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  • International Union of Crystallography
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  • 1
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    Wiley-Blackwell
    Publikationsdatum: 2024-04-07
    Beschreibung: PI3K biology; lymphoma; cancer
    Schlagwort(e): PI3K biology; lymphoma; cancer ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences
    Sprache: Englisch
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  • 2
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    Wiley-Blackwell
    Publikationsdatum: 2024-04-03
    Beschreibung: oncogenic drivers; signaling; pathways; hematologic malignancies; cancer
    Schlagwort(e): oncogenic drivers; signaling; pathways; hematologic malignancies; cancer ; thema EDItEUR::M Medicine and Nursing
    Sprache: Englisch
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  • 3
    Publikationsdatum: 2023-01-15
    Beschreibung: A Guinier camera equipped with an imaging plate is used to investigate and eliminate the sources of instrumental errors affecting the quality of the obtained scanned Guinier data. A program with a graphical user interface is presented which converts the data of the scanned images into different standard file formats for powder X‐ray patterns containing intensities, their standard deviations and the diffraction angles. The program also allows for manual and automatic correction of the 2gθ scale against a known reference material. It is shown using LaB6 that the exported X‐ray diffraction patterns provide a 2gθ scale reproducible enough to allow for averaging diffractograms obtained from different exposures of the imaging plate for the same sample. As shown on a mixture of NaCl and sodalite, the quality of the produced data is sufficient for Rietveld refinement. The software including source code is made available under a free software license.
    Beschreibung: A program for the digitization of Guinier powder diffraction images is described, which works with images from both optical and laser scanners. Thus, processing of data from storage‐phosphor‐based imaging plates and Ag‐based photographic films is possible.
    Schlagwort(e): ddc:548 ; IPreader software ; Guinier cameras ; imaging plates (IPs) ; diffraction pattern conversion into data columns ; powder X‐ray diffraction ; data processing ; Guinier method
    Sprache: Englisch
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  • 4
    Publikationsdatum: 2023-07-04
    Beschreibung: The recent diversification of macromolecular crystallographic experiments including the use of pink beams, convergent electron diffraction and serial snapshot crystallography has shown the limitations of using the Laue equations for diffraction prediction. This article gives a computationally efficient way of calculating approximate crystal diffraction patterns given varying distributions of the incoming beam, crystal shapes and other potentially hidden parameters. This approach models each pixel of a diffraction pattern and improves data processing of integrated peak intensities by enabling the correction of partially recorded reflections. The fundamental idea is to express the distributions as weighted sums of Gaussian functions. The approach is demonstrated on serial femtosecond crystallography data sets, showing a significant decrease in the required number of patterns to refine a structure to a given error.
    Beschreibung: Reflection position, size and shape prediction and partiality estimation of crystal diffraction by integrating using a Gaussian basis are described.
    Schlagwort(e): ddc:548 ; partiality estimation ; diffraction prediction ; merging ; serial snapshot crystallography
    Sprache: Englisch
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  • 5
    Publikationsdatum: 2023-07-04
    Beschreibung: Magnetic small‐angle neutron scattering (SANS) is ideally suited to providing direct reciprocal‐space information on long‐wavelength magnetic modulations, such as helicoids, solitons, merons or skyrmions. SANS of such structures in thin films or micro‐structured bulk materials is strongly limited by the tiny scattering volume vis a vis the prohibitively high background scattering by the substrate and support structures. Considering near‐surface scattering just above the critical angle of reflection, where unwanted signal contributions due to substrate or support structures become very small, it is established that the scattering patterns of the helical, conical, skyrmion lattice and fluctuation‐disordered phases in a polished bulk sample of MnSi are equivalent for conventional transmission and near‐surface SANS geometries. This motivates the prediction of a complete repository of scattering patterns expected for thin films in the near‐surface SANS geometry for each orientation of the magnetic order with respect to the scattering plane.
    Beschreibung: Near‐surface SANS is discussed for its potential as a probe of long‐wavelength magnetic modulations in specimens with reduced sample dimensions.
    Schlagwort(e): ddc:548 ; small‐angle neutron scattering ; near‐surface SANS ; magnetism ; non‐collinear magnetism ; thin films ; skyrmions ; MnSi
    Sprache: Englisch
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  • 6
    Publikationsdatum: 2023-10-24
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Complex functional materials play a crucial role in a broad range of energy‐related applications and in general for materials science. Revealing the structural mechanisms is challenging due to highly correlated coexisting phases and microstructures, especially for 〈italic〉in situ〈/italic〉 or 〈italic〉operando〈/italic〉 investigations. Since the grain sizes influence the properties, these microstructural features further complicate investigations at synchrotrons due to the limitations of illuminated sample volumes. In this study, it is demonstrated that such complex functional materials with highly correlated coexisting phases can be investigated under 〈italic〉in situ〈/italic〉 conditions with neutron diffraction. For large grain sizes, these experiments are valuable methods to reveal the structural mechanisms. For an example of 〈italic〉in situ〈/italic〉 experiments on barium titanate with an applied electric field, details of the electric‐field‐induced phase transformation depending on grain size and frequency are revealed. The results uncover the strain mechanisms in barium titanate and elucidate the complex interplay of stresses in relation to grain sizes as well as domain‐wall densities and mobilities.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉This work reports 〈italic〉in situ〈/italic〉 neutron diffraction experiments on a broad range of grain sizes of barium titanate. The study reveals the grain‐size‐dependent strain mechanisms and shows the competitiveness of neutron diffraction with high‐resolution synchrotron diffraction.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005767:jcr2vb5054:jcr2vb5054-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:550.724 ; ddc:548 ; neutron diffraction ; in situ ; applied electric fields ; barium titanate ; strain mechanisms ; grain sizes ; complex functional materials ; microstructures ; coexisting phases
    Sprache: Englisch
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  • 7
    Publikationsdatum: 2023-12-04
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉A way has been developed to measure the unit‐cell parameters of a single crystal just from an energy scan with X‐rays, even when the exact energy of the X‐rays is not well defined due to an error in the pitch angle of the monochromator. The precision of this measurement reaches 〈italic〉da〈/italic〉/〈italic〉a〈/italic〉 ∼ 1 × 10〈sup〉−5〈/sup〉. The method is based on the analysis of diffraction losses of the beam, transmitted through a single crystal (the so‐called `glitch effect'). This method can be easily applied to any transmissive X‐ray optical element made of single crystals (for example, X‐ray lenses). The only requirements are the possibility to change the energy of the generated X‐ray beam and some intensity monitor to measure the transmitted intensity. The method is agnostic to the error in the monochromator tuning and it can even be used for determination of the absolute pitch (or 2gθ) angle of the monochromator. Applying the same method to a crystal with well known lattice parameters allows determination of the exact cell parameters of the monochromator at any energy.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Diffraction losses (glitches) at certain energies of the X‐ray beam, transmitted through a single crystal, can be used for lattice parameters determination as well as for calibrating the monochromator (absolute pitch angle and the unit‐cell parameter).〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2ay5590:jsy2ay5590-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:548 ; X‐ray glitches ; diffraction losses ; unit‐cell parameter ; single‐crystal X‐ray optics ; monochromator calibration
    Sprache: Englisch
    Materialart: doc-type:article
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  • 8
    Publikationsdatum: 2023-09-12
    Beschreibung: Two data evaluation concepts for X‐ray stress analysis based on energy‐dispersive diffraction on polycrystalline materials with cubic crystal structure, almost random crystallographic texture and strong single‐crystal elastic anisotropy are subjected to comparative assessment. The aim is the study of the residual stress state in hard‐to‐reach measurement points, for which the sin2ψ method is not applicable due to beam shadowing at larger sample tilting. This makes the approaches attractive for stress analysis in engineering parts with complex shapes, for example. Both approaches are based on the assumption of a biaxial stress state within the irradiated sample volume. They exploit in different ways the elastic anisotropy of individual crystallites acting at the microscopic scale and the anisotropy imposed on the material by the near‐surface stress state at the macroscopic scale. They therefore complement each other, in terms of both their preconditions and their results. The first approach is based on the evaluation of strain differences, which makes it less sensitive to variations in the strain‐free lattice parameter a0. Since it assumes a homogeneous stress state within the irradiated sample volume, it provides an average value of the in‐plane stresses. The second approach exploits the sensitivity of the lattice strain to changes in a0. Consequently, it assumes a homogeneous chemical composition but provides a stress profile within the information depth. Experimental examples from different fields in materials science, namely shot peening of austenitic steel and in situ stress analysis during welding, are presented to demonstrate the suitability of the proposed methods.
    Beschreibung: The single‐crystal elastic anisotropy and the anisotropy of the near‐surface (residual) stress state of polycrystalline materials with random texture are exploited in energy‐dispersive X‐ray stress analysis to study samples under constrained measurement conditions.
    Schlagwort(e): ddc:548 ; X‐ray stress analysis ; energy‐dispersive diffraction ; polycrystalline materials ; single‐crystal elastic anisotropy
    Sprache: Englisch
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  • 9
    Publikationsdatum: 2023-07-20
    Beschreibung: A pseudosymmetric description of the crystal lattice derived from a single wide‐angle Kikuchi pattern can have several causes. The small size (〈15%) of the sector covered by an electron backscatter diffraction pattern, the limited precision of the projection centre position and the Kikuchi band definition are crucial. Inherent pseudosymmetries of the crystal lattice and/or structure also pose a challenge in the analysis of Kikuchi patterns. To eliminate experimental errors as much as possible, simulated Kikuchi patterns of 350 phases have been analysed using the software CALM [Nolze et al. (2021). J. Appl. Cryst.54, 1012–1022] in order to estimate the frequency of and reasons for pseudosymmetric crystal lattice descriptions. Misinterpretations occur in particular when the atomic scattering factors of non‐equivalent positions are too similar and reciprocal‐lattice points are systematically missing. As an example, a pseudosymmetry prediction depending on the elements involved is discussed for binary AB compounds with B1 and B2 structure types. However, since this is impossible for more complicated phases, this approach cannot be directly applied to compounds of arbitrary composition and structure.
    Beschreibung: Distinguishing between actual and apparent pseudosymmetry in electron backscatter diffraction patterns is nearly impossible, even for simulated patterns. However, the resulting lattice is always a superlattice as long as the signal is not a superposition of multiple patterns.
    Schlagwort(e): ddc:548 ; Bravais lattices ; pseudosymmetry ; lattice point density ; ordered/disordered structures ; lattice distortion ; electron backscatter diffraction ; backscattered Kikuchi diffraction patterns ; lattice parameters ; Funk transform
    Sprache: Englisch
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  • 10
    Publikationsdatum: 2023-07-21
    Beschreibung: Finite size effects in partial pair distribution functions generate artefacts in the scattering structure factor and scattering intensity. It is shown how they can be overcome using a binned version of the Debye scattering equation. Accordingly, reverse Monte Carlo simulations are used for very small nanoparticles of LaFeO3 with diameters below 10 nm to simultaneously analyse X‐ray scattering data and extended X‐ray absorption fine structure spectra at the La K and Fe K edges. The structural information obtained is consistent regarding local structure and long‐range order.
    Beschreibung: Computing scattering intensity using the Debye scattering equation after binning interatomic distances avoids finite size artefacts and is efficient enough for simultaneous refinement of scattering data and extended X‐ray absorption spectra by reverse Monte Carlo simulations.
    Schlagwort(e): ddc:548 ; extended X‐ray absorption fine structure ; EXAFS ; wide‐angle X‐ray scattering ; WAXS ; reverse Monte Carlo ; RMC ; nanocrystals ; LaFeO3
    Sprache: Englisch
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  • 11
    Publikationsdatum: 2023-07-21
    Beschreibung: A band width determination using the first derivative of the band profile systematically underestimates the true Bragg angle. Corrections are proposed to compensate for the resulting offset Δa/a of the mean lattice parameters derived from as many Kikuchi band widths as possible. For dynamically simulated Kikuchi patterns, Δa/a can reach up to 8% for phases with a high mean atomic number Z, whereas for much more common low‐Z materials the offset decreases linearly. A predicted offset Δa/a = f(Z) is therefore proposed, which also includes the unit‐cell volume and thus takes into account the packing density of the scatterers in the material. Since Z is not always available for unknown phases, its substitution by Zmax, i.e. the atomic number of the heaviest element in the compound, is still acceptable for an approximate correction. For simulated Kikuchi patterns the offset‐corrected lattice parameter deviation is Δa/a 〈 1.5%. The lattice parameter ratios, and the angles α, β and γ between the basis vectors, are not affected at all.
    Beschreibung: Automatically determined band widths in simulated backscatter Kikuchi patterns exhibit differences from the double Bragg angles that correlate with the scatterer density. Corrections are proposed to compensate for this.
    Schlagwort(e): ddc:548 ; mean atomic number ; Kikuchi patterns ; lattice parameters ; automated Bragg angle determination ; lattice parameter determination ; dynamical theory of electron diffraction ; electron backscatter diffraction ; Funk transform
    Sprache: Englisch
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  • 12
    Publikationsdatum: 2023-07-21
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The high‐intensity time‐of‐flight (TOF) neutron diffractometer POWTEX for powder and texture analysis is currently being built prior to operation in the eastern guide hall of the research reactor FRM II at Garching close to Munich, Germany. Because of the world‐wide 〈sup〉3〈/sup〉He crisis in 2009, the authors promptly initiated the development of 〈sup〉3〈/sup〉He‐free detector alternatives that are tailor‐made for the requirements of large‐area diffractometers. Herein is reported the 2017 enterprise to operate one mounting unit of the final POWTEX detector on the neutron powder diffractometer POWGEN at the Spallation Neutron Source located at Oak Ridge National Laboratory, USA. As a result, presented here are the first angular‐ and wavelength‐dependent data from the POWTEX detector, unfortunately damaged by a 50〈italic〉g〈/italic〉 shock but still operating, as well as the efforts made both to characterize the transport damage and to successfully recalibrate the voxel positions in order to yield nonetheless reliable measurements. Also described is the current data reduction process using the 〈italic〉PowderReduceP2D〈/italic〉 algorithm implemented in 〈italic〉Mantid〈/italic〉 [Arnold 〈italic〉et al.〈/italic〉 (2014). 〈italic〉Nucl. Instrum. Methods Phys. Res. A〈/italic〉, 〈bold〉764〈/bold〉, 156–166]. The final part of the data treatment chain, namely a novel multi‐dimensional refinement using a modified version of the 〈italic〉GSAS‐II〈/italic〉 software suite [〈ext-link ext-link-type="uri" xlink:href="http://scripts.iucr.org/cgi-bin/paper?aj5212"〉Toby & Von Dreele (2013). 〈italic〉J. Appl. Cryst.〈/italic〉〈bold〉46〈/bold〉, 544–549〈/ext-link〉], is compared with a standard data treatment of the same event data conventionally reduced as TOF diffraction patterns and refined with the unmodified version of 〈italic〉GSAS‐II〈/italic〉. This involves both determining the instrumental resolution parameters using POWGEN's powdered diamond standard sample and the refinement of a friendly‐user sample, BaZn(NCN)〈sub〉2〈/sub〉. Although each structural parameter on its own looks similar upon comparing the conventional (1D) and multi‐dimensional (2D) treatments, also in terms of precision, a closer view shows small but possibly significant differences. For example, the somewhat suspicious proximity of the 〈italic〉a〈/italic〉 and 〈italic〉b〈/italic〉 lattice parameters of BaZn(NCN)〈sub〉2〈/sub〉 crystallizing in 〈italic〉Pbca〈/italic〉 as resulting from the 1D refinement (0.008 Å) is five times less pronounced in the 2D refinement (0.038 Å). Similar features are found when comparing bond lengths and bond angles, 〈italic〉e.g.〈/italic〉 the two N—C—N units are less differently bent in the 1D results (173 and 175°) than in the 2D results (167 and 173°). The results are of importance not only for POWTEX but also for other neutron TOF diffractometers with large‐area detectors, like POWGEN at the SNS or the future DREAM beamline at the European Spallation Source.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The first real‐world neutron diffraction data have been collected with one of the POWTEX detectors (FRM II, Garching, Germany) mounted for testing at the Spallation Neutron Source (Oak Ridge National Laboratory, USA). They allow for angular‐ and wavelength‐dispersive Rietveld refinement using a modified version of 〈italic〉GSAS‐II〈/italic〉.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005767:jcr2tu5033:jcr2tu5033-fig-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:548 ; neutron detectors ; POWGEN beamline ; POWTEX detector ; DREAM beamline ; time‐of‐flight diffraction ; angular‐dispersive refinement ; wavelength‐dispersive refinement ; powder diffraction ; Rietveld refinement ; multi‐dimensional refinement
    Sprache: Englisch
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  • 13
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    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Publikationsdatum: 2023-07-21
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The paper by Gopalan [〈ext-link ext-link-type="uri" xlink:href="http://scripts.iucr.org/cgi-bin/paper?ib5086"〉(2020). 〈italic〉Acta Cryst.〈/italic〉 A〈bold〉76〈/bold〉, 318–327〈/ext-link〉] presented an enumeration of the 41 physical quantity types in non‐relativistic physics, in arbitrary dimensions, based on the formalism of Clifford algebra. Gopalan considered three antisymmetries: spatial inversion, 〈overline〉1〈/overline〉, time reversal, 1′, and wedge reversion, 1〈sup〉†〈/sup〉. A consideration of the set of all seven antisymmetries (〈overline〉1〈/overline〉, 1′, 1〈sup〉†〈/sup〉, 1′〈sup〉†〈/sup〉, 〈overline〉1〈/overline〉〈sup〉†〈/sup〉, 〈overline〉1〈/overline〉′, 〈overline〉1〈/overline〉′〈sup〉†〈/sup〉) leads to an extension of the results obtained by Gopalan. It is shown that there are 51 types of physical quantities with distinct symmetry properties in total.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉It is shown that there are 51 types of physical quantities in arbitrary dimensions with distinct transformations by wedge reversion symmetry. In the paper by 〈ext-link ext-link-type="uri" xlink:href="http://scripts.iucr.org/cgi-bin/paper?ib5086"〉Gopalan [(2020). 〈italic〉Acta Cryst.〈/italic〉 A〈bold〉76〈/bold〉, 318–327]〈/ext-link〉 only 41 types were enumerated.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:20532733:aya2ib5117:aya2ib5117-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:548 ; multivectors ; wedge reversion ; antisymmetry ; Clifford algebra
    Sprache: Englisch
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  • 14
    Publikationsdatum: 2023-07-19
    Beschreibung: The derivation of a crystal structure and its phase‐specific parameters from a single wide‐angle backscattered Kikuchi diffraction pattern requires reliable extraction of the Bragg angles. By means of the first derivative of the lattice profile, an attempt is made to determine fully automatically and reproducibly the band widths in simulated Kikuchi patterns. Even under such ideal conditions (projection centre, wavelength and lattice plane traces are perfectly known), this leads to a lattice parameter distribution whose mean shows a linear offset that correlates with the mean atomic number Z of the pattern‐forming phase. The consideration of as many Kikuchi bands as possible reduces the errors that typically occur if only a single band is analysed. On the other hand, the width of the resulting distribution is such that higher image resolution of diffraction patterns, employing longer wavelengths to produce wider bands or the use of higher interference orders is less advantageous than commonly assumed.
    Beschreibung: The lattice parameters of more than 350 phases have been determined from simulated backscatter Kikuchi patterns. The deviations correlating with the mean atomic number correspond to those observed previously for experimental electron backscatter diffraction patterns.
    Schlagwort(e): ddc:548 ; Bragg angles ; Kikuchi bands ; Kikuchi patterns ; first derivative ; lattice parameters ; lattice parameter determination ; Bravais lattice type ; electron backscatter diffraction ; Radon transform
    Sprache: Englisch
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  • 15
    Publikationsdatum: 2023-07-19
    Beschreibung: Serial crystallography experiments produce massive amounts of experimental data. Yet in spite of these large‐scale data sets, only a small percentage of the data are useful for downstream analysis. Thus, it is essential to differentiate reliably between acceptable data (hits) and unacceptable data (misses). To this end, a novel pipeline is proposed to categorize the data, which extracts features from the images, summarizes these features with the `bag of visual words' method and then classifies the images using machine learning. In addition, a novel study of various feature extractors and machine learning classifiers is presented, with the aim of finding the best feature extractor and machine learning classifier for serial crystallography data. The study reveals that the oriented FAST and rotated BRIEF (ORB) feature extractor with a multilayer perceptron classifier gives the best results. Finally, the ORB feature extractor with multilayer perceptron is evaluated on various data sets including both synthetic and experimental data, demonstrating superior performance compared with other feature extractors and classifiers.
    Beschreibung: A machine learning method for distinguishing good and bad images in serial crystallography is presented. To reduce the computational cost, this uses the oriented FAST and rotated BRIEF feature extraction method from computer vision to detect image features, followed by a multilayer perceptron (neural network) to classify the images.
    Schlagwort(e): ddc:548 ; serial crystallography ; data reduction ; machine learning ; feature extraction
    Sprache: Englisch
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  • 16
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    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Publikationsdatum: 2023-07-19
    Beschreibung: Since high‐pressure devices have been used at synchrotron facilities, accurate determination of pressure and temperature in the sample has been a crucial objective, particularly for experiments that simulate the Earth's interior. However, in some cases using a thermocouple may have a high likelihood of failure or is incompatible with a high‐pressure assembly. To address these challenges and similar issues, we aim to expand a previously proposed solution: to jointly estimate pressure and temperature (〈italic〉PT〈/italic〉) through 〈italic〉in situ〈/italic〉 X‐ray diffraction, to cover a wider range of internal 〈italic〉PT〈/italic〉 calibrants tested over larger 〈italic〉PT〈/italic〉 ranges. A modifiable Python‐based software is offered to quickly obtain results. To achieve these aims, 〈italic〉in situ〈/italic〉 large volume press experiments are performed on pellets of intimately mixed powders of a halide (NaCl, KCl, KBr, CsCl) or MgO and a metal (Pt, Re, Mo, W, Ni) in the pressure range 3–11 GPa and temperature range 300–1800 K. Although the pressure range was chosen for practical reasons, it also covers an equally important depth range in the Earth (down to 350 km) for geoscience studies. A thermocouple was used to validate the 〈italic〉PT〈/italic〉 conditions in the cell assemblies. The key results show that choosing the appropriate calibrant materials and using a joint 〈italic〉PT〈/italic〉 estimation can yield surprisingly small uncertainties (〈italic〉i.e.〈/italic〉 〈±0.1 GPa and 〈±50 K). This development is expected to benefit current and future research at extreme conditions, as other materials with high compressibility or high thermal pressure, stable over large 〈italic〉PT〈/italic〉 ranges, may be discovered and used as 〈italic〉PT〈/italic〉 calibrants.〈/p〉
    Beschreibung: Research in high‐pressure devices, such as the diamond anvil cell and the large volume press, requires knowledge of the pressure and temperature in the sample. Here, a large volume press and an internal resistive heater were used to generate high load and heat to various combinations of intimately mixed powders of materials. X‐ray diffraction and custom software were used to jointly estimate the pressures and temperatures in the samples and establish calibrants for 〈italic〉in situ〈/italic〉 experiments at extreme conditions.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2vl5008:jsy2vl5008-fig-0001"〉
    Beschreibung: https://gitlab.desy.de/robert.farla/eoscross
    Schlagwort(e): ddc:548 ; equations of state ; X‐ray diffraction ; large volume press ; high pressure ; resistive heating
    Sprache: Englisch
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  • 17
    Publikationsdatum: 2023-01-21
    Beschreibung: X‐ray diffraction with high spatial resolution is commonly used to characterize (poly)crystalline samples with, for example, respect to local strain, residual stress, grain boundaries and texture. However, the investigation of highly absorbing samples or the simultaneous assessment of high‐Z materials by X‐ray fluorescence have been limited due to the utilization of low photon energies. Here, a goniometer‐based setup implemented at the P06 beamline of PETRA III that allows for micrometre spatial resolution with a photon energy of 35 keV and above is reported. A highly focused beam was achieved by using compound refractive lenses, and high‐precision sample manipulation was enabled by a goniometer that allows up to 5D scans (three rotations and two translations). As experimental examples, the determination of local strain variations in martensitic steel samples with micrometre spatial resolution, as well as the simultaneous elemental distribution for high‐Z materials in a thin‐film solar cell, are demonstrated. The proposed approach allows users from the materials‐science community to determine micro‐structural properties even in highly absorbing samples.
    Beschreibung: A demonstration of high‐resolution micro X‐ray diffraction at high photon energies for highly absorbing samples.
    Schlagwort(e): ddc:548 ; X‐ray diffraction ; high spatial resolution ; high photon energy ; X‐ray fluorescence ; goniometers
    Sprache: Englisch
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  • 18
    Publikationsdatum: 2023-01-21
    Beschreibung: This paper presents the Domain Auto Finder (DAFi) program and its application to the analysis of single‐crystal X‐ray diffraction (SC‐XRD) data from multiphase mixtures of microcrystalline solids and powders. Superposition of numerous reflections originating from a large number of single‐crystal domains of the same and/or different (especially unknown) phases usually precludes the sorting of reflections coming from individual domains, making their automatic indexing impossible. The DAFi algorithm is designed to quickly find subsets of reflections from individual domains in a whole set of SC‐XRD data. Further indexing of all found subsets can be easily performed using widely accessible crystallographic packages. As the algorithm neither requires a priori crystallographic information nor is limited by the number of phases or individual domains, DAFi is powerful software to be used for studies of multiphase polycrystalline and microcrystalline (powder) materials. The algorithm is validated by testing on X‐ray diffraction data sets obtained from real samples: a multi‐mineral basalt rock at ambient conditions and products of the chemical reaction of yttrium and nitrogen in a laser‐heated diamond anvil cell at 50 GPa. The high performance of the DAFi algorithm means it can be used for processing SC‐XRD data online during experiments at synchrotron facilities.
    Beschreibung: This paper presents the Domain Auto Finder (DAFi) program and its application to the analysis of single‐crystal X‐ray diffraction (SC‐XRD) data from multiphase mixtures of microcrystalline solids and powders. The DAFi algorithm is designed to quickly find subsets of reflections from individual domains in a whole set of SC‐XRD data and neither requires a priori crystallographic information nor is limited by the number of phases or individual domains.
    Schlagwort(e): ddc:548 ; single‐crystal domain auto finder ; DAFi ; single‐crystal X‐ray diffraction ; polycrystalline samples ; multiphase mixtures
    Sprache: Englisch
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  • 19
    Publikationsdatum: 2023-01-25
    Beschreibung: A newly designed setup to perform steady‐state X‐ray excited optical luminescence (XEOL) spectroscopy and simultaneous XEOL and X‐ray absorption spectroscopy characterization at beamline P65 of PETRA III is described. The XEOL setup is equipped with a He‐flow cryostat and state‐of‐the‐art optical detection system, which covers a wide wavelength range of 300–1700 nm with a high spectral resolution of 0.4 nm. To demonstrate the setup functioning, low‐temperature XEOL studies on polycrystalline CuInSe2 thin film, single‐crystalline GaN thin film and single‐crystalline ZnO bulk semiconductor samples are performed.
    Beschreibung: X‐ray excited optical luminescence (XEOL) spectroscopy is increasingly important to understand the interplay between the optical properties, structure and chemical composition, providing insights into the mechanism of radiative recombination for a wide range of materials. This study demonstrates a newly implemented setup to perform steady‐state XEOL and simultaneous XEOL and XAFS characterizations at beamline P65 of PETRA III.
    Schlagwort(e): ddc:550.2 ; XEOL ; XAS ; CuInSe2 ; ZnO ; GaN
    Sprache: Englisch
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  • 20
    Publikationsdatum: 2024-03-05
    Beschreibung: Full‐field X‐ray nanoimaging is a widely used tool in a broad range of scientific areas. In particular, for low‐absorbing biological or medical samples, phase contrast methods have to be considered. Three well established phase contrast methods at the nanoscale are transmission X‐ray microscopy with Zernike phase contrast, near‐field holography and near‐field ptychography. The high spatial resolution, however, often comes with the drawback of a lower signal‐to‐noise ratio and significantly longer scan times, compared with microimaging. In order to tackle these challenges a single‐photon‐counting detector has been implemented at the nanoimaging endstation of the beamline P05 at PETRA III (DESY, Hamburg) operated by Helmholtz‐Zentrum Hereon. Thanks to the long sample‐to‐detector distance available, spatial resolutions of below 100 nm were reached in all three presented nanoimaging techniques. This work shows that a single‐photon‐counting detector in combination with a long sample‐to‐detector distance allows one to increase the time resolution for in situ nanoimaging, while keeping a high signal‐to‐noise level.
    Beschreibung: A direct photon‐counting detector was used for different nanoimaging phase contrast techniques, increasing the temporal resolution.
    Schlagwort(e): ddc:548 ; nanotomography ; full‐field X‐ray microscopy ; near‐field holography ; near‐field ptychography ; Zernike phase contrast ; single‐photon‐counting detector ; phase contrast
    Sprache: Englisch
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  • 21
    Publikationsdatum: 2024-02-14
    Beschreibung: X‐ray crystallography has witnessed a massive development over the past decade, driven by large increases in the intensity and brightness of X‐ray sources and enabled by employing high‐frame‐rate X‐ray detectors. The analysis of large data sets is done via automatic algorithms that are vulnerable to imperfections in the detector and noise inherent with the detection process. By improving the model of the behaviour of the detector, data can be analysed more reliably and data storage costs can be significantly reduced. One major requirement is a software mask that identifies defective pixels in diffraction frames. This paper introduces a methodology and program based upon concepts of machine learning, called robust mask maker (RMM), for the generation of bad‐pixel masks for large‐area X‐ray pixel detectors based on modern robust statistics. It is proposed to discriminate normally behaving pixels from abnormal pixels by analysing routine measurements made with and without X‐ray illumination. Analysis software typically uses a Bragg peak finder to detect Bragg peaks and an indexing method to detect crystal lattices among those peaks. Without proper masking of the bad pixels, peak finding methods often confuse the abnormal values of bad pixels in a pattern with true Bragg peaks and flag such patterns as useful regardless, leading to storage of enormous uninformative data sets. Also, it is computationally very expensive for indexing methods to search for crystal lattices among false peaks and the solution may be biased. This paper shows how RMM vastly improves peak finders and prevents them from labelling bad pixels as Bragg peaks, by demonstrating its effectiveness on several serial crystallography data sets.
    Beschreibung: Attention is focused on perhaps the biggest bottleneck in data analysis for serial crystallography at X‐ray free‐electron lasers, which has not received serious enough examination to date. An effective and reliable way is presented to identify anomalies in detectors, using machine learning and recently developed mathematical methods in the field referred to as `robust statistics'. image
    Schlagwort(e): ddc:548 ; bad‐pixel masks ; robust mask maker ; machine learning ; robust statistics ; serial crystallography
    Sprache: Englisch
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  • 22
    Publikationsdatum: 2024-02-14
    Beschreibung: Machine learning (ML) has received enormous attention in science and beyond. Discussed here are the status, opportunities, challenges and limitations of ML as applied to X‐ray and neutron scattering techniques, with an emphasis on surface scattering. Typical strategies are outlined, as well as possible pitfalls. Applications to reflectometry and grazing‐incidence scattering are critically discussed. Comment is also given on the availability of training and test data for ML applications, such as neural networks, and a large reflectivity data set is provided as reference data for the community.
    Beschreibung: The status, opportunities, challenges and limitations of machine learning are discussed as applied to X‐ray and neutron scattering techniques, with an emphasis on surface scattering.
    Schlagwort(e): ddc:548 ; surface scattering ; X‐ray diffraction ; neutron scattering ; machine learning ; data analysis
    Sprache: Englisch
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  • 23
    Publikationsdatum: 2024-02-21
    Beschreibung: The storage ring upgrade of the European Synchrotron Radiation Facility makes ESRF–EBS the most brilliant high‐energy fourth‐generation light source, enabling in situ studies with unprecedented time resolution. While radiation damage is commonly associated with degradation of organic matter such as ionic liquids or polymers in the synchrotron beam, this study clearly shows that highly brilliant X‐ray beams readily induce structural changes and beam damage in inorganic matter, too. Here, the reduction of Fe3+ to Fe2+ in iron oxide nanoparticles by radicals in the brilliant ESRF–EBS beam, not observed before the upgrade, is reported. Radicals are created due to radiolysis of an EtOH–H2O mixture with low EtOH concentration (∼6 vol%). In light of extended irradiation times during insitu experiments in, for example, battery and catalysis research, beam‐induced redox chemistry needs to be understood for proper interpretation of insitu data.
    Beschreibung: With the increased brilliance at the European Research Facility–Extremely Brilliant Source (ESRF–EBS), a beam‐induced reduction of non‐stochiometric iron oxide nanoparticles (almost maghemite composition) to magnetite was observed in a mixture of ethanol and water with low ethanol concentration.
    Schlagwort(e): ddc:548 ; beam‐induced radiolysis ; radiation damage on inorganic materials ; ESRF–EBS
    Sprache: Englisch
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  • 24
    facet.materialart.
    Unbekannt
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Publikationsdatum: 2024-02-22
    Beschreibung: Small‐angle scattering is an increasingly common method for characterizing particle ensembles in a wide variety of sample types and for diverse areas of application. SASfit has been one of the most comprehensive and flexible curve‐fitting programs for decades, with many specialized tools for various fields. Here, a selection of enhancements and additions to the SASfit program are presented that may be of great benefit to interested and advanced users alike: (a) further development of the technical basis of the program, such as new numerical algorithms currently in use, a continuous integration practice for automated building and packaging of the software, and upgrades on the plug‐in system for easier adoption by third‐party developers; (b) a selection of new form factors for anisotropic scattering patterns and updates to existing form factors to account for multiple scattering effects; (c) a new type of a very flexible distribution called metalog [Keelin (2016). Decis. Anal.13, 243–277], and regularization techniques such as the expectation‐maximization method [Dempster et al. (1977). J. R. Stat. Soc. Ser. B (Methodological), 39, 1–22; Richardson (1972) J. Opt. Soc. Am.62, 55; Lucy (1974). Astron. J.79, 745; Lucy (1994). Astron. Astrophys.289, 983–994], which is compared with fits of analytical size distributions via the non‐linear least‐squares method; and (d) new structure factors, especially for ordered nano‐ and meso‐scaled material systems, as well as the Ornstein–Zernike solver for numerical determination of particle interactions and the resulting structure factor when no analytical solution is available, with the aim of incorporating its effects into the small‐angle scattering intensity model used for fitting with SASfit.
    Beschreibung: Recent enhancements and additions to the SASfit program are discussed, including anisotropic scattering models, flexible distributions, regularization techniques such as the expectation‐maximization method, and new structure factors, especially for ordered nano‐ and meso‐scaled material. The Ornstein–Zernike solver for numerical structure factors is also introduced. image
    Schlagwort(e): ddc:548 ; small‐angle scattering ; SASfit ; numerical models ; structure factors ; form factors ; regularization techniques
    Sprache: Englisch
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  • 25
    Publikationsdatum: 2024-02-05
    Beschreibung: A modulation of intensity with zero effort (MIEZE) setup is proposed for high‐resolution neutron spectroscopy at momentum transfers up to 3 Å〈sup〉−1〈/sup〉, energy transfers up to 20 meV and an energy resolution in the microelectronvolt range using both thermal and cold neutrons. MIEZE has two prominent advantages compared with classical neutron spin echo. The first is the possibility to investigate spin‐depolarizing samples or samples in strong magnetic fields without loss of signal amplitude and intensity. This allows for the study of spin fluctuations in ferromagnets, and facilitates the study of samples with strong spin‐incoherent scattering. The second advantage is that multi‐analyzer setups can be implemented with comparatively little effort. The use of thermal neutrons increases the range of validity of the spin‐echo approximation towards shorter spin‐echo times. In turn, the thermal MIEZE option for greater ranges (TIGER) closes the gap between classical neutron spin‐echo spectroscopy and conventional high‐resolution neutron spectroscopy techniques such as triple‐axis, time‐of‐flight and back‐scattering. To illustrate the feasibility of TIGER, this paper presents the details of its implementation at the RESEDA beamline at FRM II by means of an additional velocity selector, polarizer and analyzer.
    Beschreibung: A modulation of intensity with zero effort (MIEZE) setup is proposed for high‐resolution neutron spectroscopy at momentum transfers up to 3 Å〈sup〉−1〈/sup〉, energy transfers up to 20 meV and an energy resolution in the microelectronvolt range using both thermal and cold neutrons.
    Schlagwort(e): ddc:548 ; neutron resonant spin echo ; MIEZE ; quasielastic scattering ; thermal neutrons
    Sprache: Englisch
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  • 26
    Publikationsdatum: 2024-02-05
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Penetrating, high‐energy synchrotron X‐rays are in strong demand, particularly for high‐pressure research in physics, chemistry and geosciences, and for materials engineering research under less extreme conditions. A new high‐energy wiggler beamline P61 has been constructed to meet this need at PETRA III in Hamburg, Germany. The first part of the paper offers an overview of the beamline front‐end components and beam characteristics. The second part describes the performance of the instrumentation and the latest developments at the P61B endstation. Particular attention is given to the unprecedented high‐energy photon flux delivered by the ten wigglers of the PETRA III storage ring and the challenges faced in harnessing this amount of flux and heat load in the beam. Furthermore, the distinctiveness of the world's first six‐ram Hall‐type large‐volume press, Aster‐15, at a synchrotron facility is described for research with synchrotron X‐rays. Additionally, detection schemes, experimental strategies and preliminary data acquired using energy‐dispersive X‐ray diffraction and radiography techniques are presented.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉The operation of the P61B endstation large‐volume press and optics of P61 are reviewed. The instrumentation at P61B, including the large‐volume press, detection systems and data acquisition for 〈italic〉in situ〈/italic〉 high‐pressure experiments are described.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2ju5040:jsy2ju5040-fig-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:550.724 ; extreme conditions ; high‐pressure ; large‐volume press ; energy‐dispersive X‐ray diffraction ; radiography ; resistive heating ; ultrasonic interferometry ; acoustic emissions detection
    Sprache: Englisch
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  • 27
    facet.materialart.
    Unbekannt
    International Union of Crystallography | 5 Abbey Square, Chester, Cheshire CH1 2HU, England
    Publikationsdatum: 2023-12-12
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Studying electron‐ and X‐ray‐induced electron cascades in solids is essential for various research areas at free‐electron laser facilities, such as X‐ray imaging, crystallography, pulse diagnostics or X‐ray‐induced damage. To better understand the fundamental factors that define the duration and spatial size of such cascades, this work investigates the electron propagation in ten solids relevant for the applications of X‐ray lasers: Au, B〈sub〉4〈/sub〉C, diamond, Ni, polystyrene, Ru, Si, SiC, Si〈sub〉3〈/sub〉N〈sub〉4〈/sub〉 and W. Using classical Monte Carlo simulation in the atomic approximation, we study the dependence of the cascade size on the incident electron or photon energy and on the target parameters. The results show that an electron‐induced cascade is systematically larger than a photon‐induced cascade. Moreover, in contrast with the common assumption, the maximal cascade size does not necessarily coincide with the electron range. It was found that the cascade size can be controlled by careful selection of the photon energy for a particular material. Photon energy, just above an ionization potential, can essentially split the absorbed energy between two electrons (photo‐ and Auger), reducing their initial energy and thus shrinking the cascade size. This analysis suggests a way of tailoring the electron cascades for applications requiring either small cascades with a high density of excited electrons or large‐spread cascades with lower electron densities.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Studying electron‐ and X‐ray‐induced electron cascades in solids is essential for various research areas at free‐electron laser facilities, such as X‐ray imaging, crystallography, pulse diagnostics or X‐ray‐induced damage. To better understand the fundamental factors that define the duration and spatial size of such cascades, this work investigates the electron propagation in ten solids relevant for the applications of X‐ray lasers. Using classical Monte Carlo simulation in the atomic approximation, the dependence of the cascade size on the incident electron or photon energy and on the target parameters is studied.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005775:jsy2gb5123:jsy2gb5123-fig-0001"〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:548 ; electron cascades ; X‐ray free‐electron lasers ; Monte Carlo ; photon‐induced cascade ; electron transport
    Sprache: Englisch
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  • 28
    Publikationsdatum: 2023-12-14
    Beschreibung: In Bragg coherent diffractive imaging, the precise location of the measured crystals in the interior of the sample is usually missing. Obtaining this information would help the study of the spatially dependent behavior of particles in the bulk of inhomogeneous samples, such as extra‐thick battery cathodes. This work presents an approach to determine the 3D position of particles by precisely aligning them at the instrument axis of rotation. In the test experiment reported here, with a 60 µm‐thick LiNi0.5Mn1.5O4 battery cathode, the particles were located with a precision of 20 µm in the out‐of‐plane direction, and the in‐plane coordinates were determined with a precision of 1 µm.
    Beschreibung: A method to determine the 3D position of particles in Bragg coherent diffractive imaging experiments is proposed. Test measurements demonstrate depth‐resolution with a precision of 20 µm along the beam. image
    Schlagwort(e): ddc:548 ; extra‐thick battery cathodes ; Bragg coherent X‐ray diffractive imaging ; battery cathodes ; Bragg diffraction ; sphere of confusion ; 3D mapping
    Sprache: Englisch
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  • 29
    Publikationsdatum: 2024-01-12
    Beschreibung: A split‐and‐delay unit for the extreme ultraviolet and soft X‐ray spectral regions has been built which enables time‐resolved experiments at beamlines FL23 and FL24 at the Free‐electron LASer in Hamburg (FLASH). Geometric wavefront splitting at a sharp edge of a beam splitting mirror is applied to split the incoming soft X‐ray pulse into two beams. Ni and Pt coatings at grazing incidence angles have been chosen in order to cover the whole spectral range of FLASH2 and beyond, up to hν = 1800 eV. In the variable beam path with a grazing incidence angle of ϑd = 1.8°, the total transmission (T) ranges are of the order of 0.48 〈 T 〈 0.84 for hν 〈 100 eV and T 〉 0.50 for 100 eV 〈 hν 〈 650 eV with the Ni coating, and T 〉 0.06 for hν 〈 1800 eV for the Pt coating. For a fixed beam path with a grazing incidence angle of ϑf = 1.3°, a transmission of T 〉 0.61 with the Ni coating and T 〉 0.23 with a Pt coating is achieved. Soft X‐ray pump/soft X‐ray probe experiments are possible within a delay range of −5 ps 〈 Δt 〈 +18 ps with a nominal time resolution of tr = 66 as and a measured timing jitter of tj = 121 ± 2 as. First experiments with the split‐and‐delay unit determined the averaged coherence time of FLASH2 to be τc = 1.75 fs at λ = 8 nm, measured at a purposely reduced coherence of the free‐electron laser.
    Beschreibung: The properties of the recently installed split‐and‐delay unit at beamlines FL23 and FL24 at FLASH2 are presented. Its operational range, performance parameters and results of a first experiment are described. image
    Schlagwort(e): ddc:550.724 ; time‐resolved pump–probe ; XUV ; soft X‐rays ; free‐electron laser
    Sprache: Englisch
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  • 30
    Publikationsdatum: 2024-01-12
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉〈italic〉XDSGUI〈/italic〉 is a lightweight graphical user interface (GUI) for the 〈italic〉XDS〈/italic〉, 〈italic〉SHELX〈/italic〉 and 〈italic〉ARCIMBOLDO〈/italic〉 program packages that serves both novice and experienced users in obtaining optimal processing and phasing results for X‐ray, neutron and electron diffraction data. The design of the program enables data processing and phasing without command line usage, and supports advanced command flows in a simple user‐modifiable and user‐extensible way. The GUI supplies graphical information based on the tabular log output of the programs, which is more intuitive, comprehensible and efficient than text output can be.〈/p〉
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉A customizable stateless graphical user interface simplifies the processing, analysis and phasing of diffraction data.〈boxed-text position="anchor" content-type="graphic" xml:lang="en"〉〈graphic position="anchor" id="jats-graphic-1" xlink:href="urn:x-wiley:16005767:jcr2yr5110:jcr2yr5110-fig-0001"〉 〈alt-text〉image〈/alt-text〉 〈/graphic〉〈/boxed-text〉〈/p〉
    Schlagwort(e): ddc:548 ; X‐ray diffraction ; neutron diffraction ; electron diffraction ; data processing ; graphical user interfaces ; phasing ; XDS ; ARCIMBOLDO ; SHELX
    Sprache: Englisch
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  • 31
    Publikationsdatum: 2024-01-31
    Beschreibung: The response of permafrost to submergence can vary between ice-rich late Pleistocene deposits and the thermokarst basins that thawed out during the Holocene. We hypothesize that inundated Alases offshore thaw faster than submerged Yedoma. To test this hypothesis, we estimated depths to the top of ice-bearing permafrost offshore of the Bykovsky Peninsula in northeast Siberia using electrical resistivity surveys. The surveys traversed submerged lagoon deposits, drained and refrozen Alas deposits, and undisturbed Yedoma from the coastline to 373 m offshore. While the permafrost degradation rates of the submerged Yedoma were in the range of similar sites, the submerged Alas permafrost degradation rates were up to 170% faster. Given the abundance of thermokarst basins and lakes along parts of the Arctic coastline, its effect on subsea permafrost degradation must be similarly prevalent. Remote sensing analyses suggest that 54% of lagoons wider than 500 m originated in thermokarst basins.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 32
    Publikationsdatum: 2024-01-31
    Beschreibung: Permafrost thaw leads to thermokarst lake formation and talik growth tens of meters deep, enabling microbial decomposition of formerly frozen organic matter (OM). We analyzed two 17-m-long thermokarst lake sediment cores taken in Central Yakutia, Russia. One core was from an Alas lake in a Holocene thermokarst basin that underwent multiple lake generations, and the second core from a young Yedoma upland lake (formed ca. 70 years ago) whose sediments have thawed for the first time since deposition. This comparison provides a glance into OM fate in thawing Yedoma deposits. We analyzed total organic carbon (TOC) and dissolved organic carbon (DOC) content, n-alkanes concentrations, and bacterial and archaeal membrane markers. Furthermore, we conducted one-year-long incubations (4 °C, dark) and measured anaerobic carbon dioxide (CO2) and methane (CH4) production. The sediments from both cores contained little TOC (0.7±0.4 wt%), but DOC values were relatively high, with highest values in the frozen Yedoma lake sediments (1620 mg L-1). Cumulative GHG production after one year was highest in the Yedoma lake sediments (226±212 μg CO2-C gdw-1, 28±36 μg CH4-C gdw-1) and 3 and 1.5 times lower in the Alas lake sediments, respectively (75±76 μg CO2-C gdw-1, 19±29 μg CH4-C gdw-1). The highest CO2 production in the frozen Yedoma lake sediments likely results from decomposition of readily bioavailable OM, while highest CH4 production in the non-frozen top sediments of this core suggests that methanogenic communities established upon thaw. The lower GHG production in the non-frozen Alas lake sediments resulted from advanced OM decomposition during Holocene talik development. Furthermore, we found that drivers of CO2 and CH4 production differ following thaw. Our results suggest that GHG production from TOC-poor mineral deposits, which are widespread throughout the Arctic, can be substantial. Therefore, our novel data are relevant for vast ice-rich permafrost deposits vulnerable to thermokarst formation.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 33
    facet.materialart.
    Unbekannt
    Wiley-Blackwell
    In:  EPIC3Permafrost and Periglacial Processes, Wiley-Blackwell, 32(1), pp. 59-75, ISSN: 1045-6740
    Publikationsdatum: 2024-01-31
    Beschreibung: Thermal erosion is a major mechanism of permafrost degradation, resulting in characteristic landforms. We inventory thermo-erosional valleys in ice-rich coastal lowlands adjacent to the Siberian Laptev Sea based on remote sensing, Geographic Information System (GIS), and field investigations for a first regional assessment of their spatial distribution and characteristics. Three study areas with similar geological (Yedoma Ice Complex) but diverse geomorphological conditions vary in valley areal extent, incision depth, and branching geometry. The most extensive valley networks are incised deeply (up to 35 m) into the broad inclined lowland around Mamontov Klyk. The flat, low-lying plain forming the Buor Khaya Peninsula is more degraded by thermokarst and characterized by long valleys of lower depth with short tributaries. Small, isolated Yedoma Ice Complex remnants in the Lena River Delta predominantly exhibit shorter but deep valleys. Based on these hydrographical network and topography assessments, we discuss geomorphological and hydrological connections to erosion processes. Relative catchment size along with regional slope interact with other Holocene relief-forming processes such as thermokarst and neotectonics. Our findings suggest that thermo-erosional valleys are prominent, hitherto overlooked permafrost degradation landforms that add to impacts on biogeochemical cycling, sediment transport, and hydrology in the degrading Siberian Yedoma Ice Complex.
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  • 34
    Publikationsdatum: 2024-03-13
    Beschreibung: The PERCIVAL detector is a CMOS imager designed for the soft X‐ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free‐electron laser, holographic imaging at a storage ring and preliminary tests on X‐ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X‐ray science.
    Schlagwort(e): ddc:548 ; X‐ray detectors ; soft X‐rays ; ptychography ; holographic imaging ; XPCS ; detectors
    Sprache: Englisch
    Materialart: doc-type:article
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  • 35
    Publikationsdatum: 2024-03-22
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , peerRev
    Format: application/pdf
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  • 36
    facet.materialart.
    Unbekannt
    Wiley-Blackwell
    In:  EPIC3Reviews in Aquaculture, Wiley-Blackwell, ISSN: 1753-5123
    Publikationsdatum: 2024-05-06
    Beschreibung: Mass mortality events (MMEs) are defined as the death of large numbers of fish over a short period of time. These events can result in catastrophic losses to the Atlantic salmon aquaculture industry and the local economy. However, they are challenging to understand because of their relative infrequency and the high number of potential factors involved. As a result, the causes and consequences of MMEs in Atlantic salmon aquaculture are not well understood. In this study, we developed a structural network of causal risk factors for MMEs for aquaculture and the communities that depend on Atlantic salmon aquaculture. Using the Interpretive Structural Modeling (ISM) technique, we analysed the causes of Atlantic salmon mass mortalities due to environmental (abiotic), biological (biotic) and nutritional risk factors. The consequences of MMEs were also assessed for the occupational health and safety of aquaculture workers and their implications for the livelihoods of local communities. This structural network deepens our understanding of MMEs and points to management actions and interventions that can help mitigate mass mortalities. MMEs are typically not the result of a single risk factor but are caused by the systematic interaction of risk factors related to the environment, fish diseases, feeding/nutrition and cage-site management. Results also indicate that considerations of health and safety risk, through pre- and post-event risk assessments, may help to minimize workplace injuries and eliminate potential risks of human fatalities. Company and government assisted socio-economic measures could help mitigate post-mass mortality impacts. Appropriate and timely management actions may help reduce MMEs at Atlantic salmon cage sites and minimize the physical and social vulnerabilities of workers and local communities.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 37
    Publikationsdatum: 2024-04-25
    Beschreibung: 〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉〈italic〉INSIGHT〈/italic〉 is a Python‐based software tool for processing and reducing 2D grazing‐incidence wide‐ and small‐angle X‐ray scattering (GIWAXS/GISAXS) data. It offers the geometric transformation of the 2D GIWAXS/GISAXS detector image to reciprocal space, including vectorized and parallelized pixel‐wise intensity correction calculations. An explicit focus on efficient data management and batch processing enables full control of large time‐resolved synchrotron and laboratory data sets for a detailed analysis of kinetic GIWAXS/GISAXS studies of thin films. It processes data acquired with arbitrarily rotated detectors and performs vertical, horizontal, azimuthal and radial cuts in reciprocal space. It further allows crystallographic indexing and GIWAXS pattern simulation, and provides various plotting and export functionalities. Customized scripting offers a one‐step solution to reduce, process, analyze and export findings of large 〈italic〉in situ〈/italic〉 and 〈italic〉operando〈/italic〉 data sets.〈/p〉
    Schlagwort(e): ddc:548 ; grazing‐incidence X‐ray scattering ; time‐resolved studies ; in situ studies ; operando studies ; computer programs
    Sprache: Englisch
    Materialart: doc-type:article
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  • 38
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 9-20 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Einfluß von 3-Phenylenbismaleimid auf die Werkstoffeigenschaften von CaCO3 gefüllten Polypropylen-Verbundstoffen wurde untersucht. Die Verarbeitungstemperatur spielte eine entscheidende Rolle bei der Herstellung der Verbundwerkstoffe. Bei Verarbeitungstemperaturen oberhalb der Bismaleimid-Zersetzungstemperatur zeigte die Bismaleimid-Verbindung einen positiven Effekt. Die chemische Zusammensetzung der modifizierten Verbunde wurde mit den mechanischen Eigenschaften korreliert. Basierend auf ESCA-Analysen werden Wechselwirkungen zwischen dem Polymeren und CaCO, diskutiert.
    Notizen: The effect of 3-phenylene bismaleimide on the mechanical performance of an inorganic filler-based polypropylene composite was studied. The selection of processing temperature played a significant role in the preparation of such composites. A positive effect of the bismaleimide compound was obtained for a processing temperature above the decomposition temperature of bismaleimide. The chemical composition of the modified composite was correlated to its mechanical strength by experimentation involving a rotatable design. An interaction between polymer and CaCO3 has been proposed based on ESCA analysis.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 39
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 33-48 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Chemische und mechanische Eigenschaften von Zwischenprodukten der PE-Schrumpfschlauch-Produktion wurden bei unterschiedlichen Compound-Zusammensetzungen (PE, ein aromatisches Amin oder Phenolderivat als Antioxidans und in einigen Fällen ein Flammschutzmittel und/oder eine Elastomerkomponente) untersucht.Während der Herstellung, besonders während der durch Elektronenstrahlung initiierten Vernetzung, nimmt die thermooxidative Stabilität des Materials gegenüber der des compoundierten Granulats ab. Das aromatische Amin scheint bei gleicher Zusammensetzung das wirksamere und strahlungsbeständigere Antioxidans im Vergleich zum Phenolderivat zu sein. Die Oxidationsstabilität der hergestellten Schrumpfschläuche wird nicht von der Qualität des eingesetzten PE-Ausgangsgranulats beeinflußt.Durch die Alterung des Materials ändern sich die mechanischen Eigenschaften geringfügig. Die Elastomerzugabe bewirkt keine Änderung von Zugfestigkeit und Reißdehnung. Die Stabilität des Endprodukts ist bei weitem ausreichend, um den Spannungen, die beim Schrumpfen während des Gebrauchs auftreten, standzuhalten. Die gute Zugfestigkeit des Materials wird durch die Alterung ebenfalls nicht beeinträchtigt.Bei der Extrusion des Granulats tritt keine nennenswerte Änderung des Molekulargewichts bzw. der Molekulargewichtsverteilung auf. Durch die Bestrahlung wird das Material vernetzt und zu mehr als 50% unlöslich, und seine thermooxidativen Eigenschaften ändern sich deutlich gegenüber dem ursprünglichen PE und dem daraus compoundierten Material.
    Notizen: Some chemical and mechanical properties of intermediate products obtained in the production of PE heat-shrinkable tubes were studied at different compositions of the material containing PE, antioxidant (aromatic amime or phenol) and, in some cases, flame retardant and/or an elastomer.In the course of the production phase, the thermooxidative stability decreases compared to that of compounded granulate. The greatest decrease is caused by irradiation. The aromatic amine seems to be a more effective antioxidant at similar compositions than the phenol derivative, and it shows a better resistance against irradiation. The oxidative stability of the finished shrinkable tubes is not affected by the quality of commercial granulate (initial polyethylene).Mechanical properties change slightly upon ageing, and the introduction of the elastomer did not alter the tensile strength and elongation at break. The remaining stability of the end product was still high enough to bear the stress of shrinking in use, and the good tensile strength of the material did not decrease upon thermal ageing either.In the extrusion of the granulated compound no significant change in the distribution and average molecular weight took place. Irradiation produced more than 50% insoluble fraction and the thermooxidative properties of the crosslinked sample changed significantly compared to the original PE and to the compound prepared from it.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 40
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 89-96 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: In the present work oxygen index (OI) measurements and thermogravimetric analysis (TG) for a series of polyurethanes based on diols and isocyanate were conducted. It was found that a correlation exists between some of the thermal degradation parameters obtained from TG and OI-values. Analysis of experimental results confirms that the amount of mass loss at 250°C is directly proportional to the OI-value. It was also found that the logarithmic temperatures of maximal decomposition rates are directly proportional to the OI-values.
    Notizen: In der vorliegenden Arbeit wurden für eine Serie von Polyurethanen auf der Basis von Diol und Isocyanat der Sauerstoffindex (SI) gemessen und die thermische Zersetzung mittels thermogravimetrischer Analyse (TG) untersucht. Dabei wurde ein Zusammenhang zwischen einigen Parametern der thermischen Zersetzung und den SI-Werten gefunden. Die Auswertung der experimentellen Ergebnisse zeigte, daß die Höhe des Massenverlustes bei 250°C und die SI-Werte direkt proportional zueinander sind. Derselbe Zusammenhang besteht auch zwischen dem Logarithmus der Temperatur bei der maximalen Zersetzungsgeschwindigkeit und den SI-Werten.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 41
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 109-114 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Poly(acrylsäre-co-acrylamid) wurde mit Zinkoxid und Kryolith (Na3AlF6) in unterschiedlichen Verhältnissen gemischt und bei Raumtemperatur zu Zahnzementen ausgehärtet. IPDT, Temperaturen bei maximaler Abbaugeschwindigkeit, Aktivierungsenergien und Frequenzfaktoren des thermischen Abbaus der Proben wurden aus thermogravimetrischen Messungen ermittelt. Die Probe mit 20 Gew.-% Kryolith in der Füllstoffmischung ist thermisch sehr stabil.
    Notizen: Dental cement compositions made by mixing poly(acrylic acid-co-acrylamide) and mixtures of zinc oxide and cryolite (Na3AIF6) in various proportions of 10-50 wt.-% (w/w) were cured at room temperature. From thermogravimetric analyses of the samples, the integral procedural decomposition temperatures (IPDT), maximum decomposition temperatures, activation energies and frequency factors were evaluated. The cured cement sample containing 20 wt.-% cryolite in the filler mixture is thermally very stable.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 42
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 133-144 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die wasserlöslichen aromatischen Diazonium-Doppelsalze p-Diazodiphenylaminchlorid/Zinkchlorid (DZS-1) und p-Diazoanisolchlorid/Zinkchlorid (DZS-2) wurden auf ihre Verwendbarkeit als photobleichbare Farbstoffe in der Kontrastverstärkungslithographie untersucht. Nach Untersuchung der Bleicheigenschaften der hergestellten Salze wurde DZS-1 in wäßrigen Lösungen mit Poly(vinylalkohol) als Kontrastverstärkungssystem eingesetzt. Die thermische Stabilität, der Resistkontrast, die Bestrahlungsparameter und andere Bleicheigenschaften wurden untersucht. Im Vergleich zu einem handelsüblichen i-Linien-Photoresist beträgt das Kontrastverhältnis der DZS-1/PVA CEL-Schicht 1,67.
    Notizen: Water soluble aromatic diazonium double salts, p-diazodiphenylamine chloride zinc chloride (DZS-1) and p-diazoanisol chloride zinc chloride (DZS-2), have been evaluated as photobleachable dyes for contrast enhancement lithography. After testing the bleaching characteristics, aqueous solutions of DZS-1 and poly(vinyl alcohol) were used as a contrast enhancement material. Thermal stability, resist contrast, exposure parameters and other bleaching characteristics of the photobleachable membranes were investigated. A. commercial i-line photoresist was used to evaluate the contrast ratio of the DZS-1/PVA CEL layer. The contrast ratio obtained in this investigation is 1.67.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 43
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 167-178 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Methylen-4,4′-diphenyldiisocyanat und zwei unterschiedliche Bisoxazoline wurden für Kopplungsreaktionen in mit Carboxygruppen terminierten flüssigkristallinen Poly(ethylenterephthalat-co-oxybenzoat)en eingesetzt. Um definierte Bedingungen zu gewährleisten, erfolgte die Synthese von Copolyestern mit unterschiedlichen Carboxygruppenkonzentrationen. Die Bestimmung des Carboxygruppengehalts wird beschrieben.Es erfolgt ein Vergleich des Kopplungsverhaltens beider Arten von Kettenverlängerern. Es konnte nachgewiesen werde, daß die Bisoxazoline bedeutend schneller reagieren als das Diisocyanat. Durch einen geringen Überschuß and Bisoxazolin in der Reaktionsmischung konnte einer thermischen Schädigung vorgebeugt werden. Abhängig von der Menge an zugegebenem Koppler wurden bei den modifizierten Copolyestern Oxazolinendgruppen beobachtet. Außerdem werden mögliche Vernetzungsreaktionen und die thermische Stabilität diskutiert.
    Notizen: Methylene-4,4′-diphenyldiisocyanate and two different bisoxazolines were used for coupling reactions in carboxy-terminated liquid crystalline poly(ethylene terephthalate-co-oxybenzoate). In order to guarantee defined conditions, copolyesters with different carboxylic group concentrations were synthesized. The determination of the carboxylic group content is described.The coupling behaviour of both types of chain extenders has been compared. It was evidenced that the bisoxazolines reacted significantly faster than the diisocyanate. A slight excess of bisoxazoline in the reaction mixture prevented thermomechanical degradation. Depending on the amount of coupling agent added, an oxazoline termination of the copolyester was observed. Additionally, probable crosslinking reactions and the thermal stability have been discussed.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 44
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 224 (1995), S. 201-201 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 45
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 11-20 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Einfluß von 3-Phenylenbismaleimid auf die Werkstoffeigenschaften von mit Talkum und Zeolith gefüllten Polypropylen-Verbundstoffen wurde untersucht. Durch geeignete Planung des Aufbaus kann die Produkteigenschaft optimiert werden. Die Kapazität zur Füllstoffaufnahme schwankt bei Polypropylen je nach Art des Füllstoffs. Ein hochbelastbarer Verbundstoff kann aus einem geeignet modifizierten, mit Zeolith gefüllten Polypropylen hergestellt werden, auch wenn der Füllstoff in der Verbundmatrix dominiert. Als Ursache dieser Verstärkung wird eine verbesserte Wechselwirkung zwischen dem Polymeren und dem Füllstoff angenommen.
    Notizen: The effect of 3-phenylene bismaleimide as a modifier for talc and zeolite-filled polypropylene composites has been studied. The usefulness of the experimental design to assure best product properties has also been illustrated. Polypropylene shows a variable degree of filling capacity depending on the type of filler. A high-strength composite can be prepared with suitably modified zeolite-filled polypropylene even if filler is the dominant phase in the composite matrix. An improved interfacial interaction between polypropylene and filler is proposed to be the reason for this improvement of strength.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 46
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 51-61 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die katalytische Oligomerisation von 1-Decen wurde mit Komplexverbindungen mehrerer Übergangsmetalle (Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V)) und Alkyl-aluminiumhalogeniden als Cokatalysatoren durchgeführt. Mit einem Chrom(III)-Et3Al2Cl3-Katalysatorsystem konnten Dimere (C20), Trimere (C30) und Tetramere (C40) von 1-Decen erhalten werden. Die kinematischen Viskositäten und Fließpunkte der hydrierten Oligomere wurden bestimmt und mit den Werten handelsüblicher Proben verglichen. Ein Mechanismus für die Oligomerisation von 1-Decen mit diesem Katalysatorsystem wird vorgeschlagen.
    Notizen: The catalytic oligomerization of 1-decene has been carried out employing several transition metal complexes of Co(II), Co(III), Zr(IV), Ti(IV), Cr(III), V(V) in combination with alkyl aluminum halides as cocatalysts. The chromium(III)-Et3Al2Cl3 system exhibits good oligomerizing activity yielding dimers (C20), trimers (C30) and tetramers (C40) of 1-decene. The kinematic viscosities and pour points of hydrogenated oligomers have been determined and compared with those of commercial samples. The probable mechanism of oligomerization of 1-decene on this catalyst is described.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 47
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 99-107 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Single-component formulations of epoxy resins with reactive accelerators must be storable. The preparation of several blocked accelerators is described. The basicity of tertiary amines, which correlates with accelerating effects, as well as acidity and structure of polyphenols and modified novolacs influences the extend of blocking. The curing process was investigated by measurements of gel time and viscosity.
    Notizen: Einkomponentige Epoxidharzsysteme mit effizienten Reaktionsbeschleunigern müssen lagerstabil sein. Daher wurden Versuche unternommen, Beschleuniger auf Basis von tertiären Aminen mit modifizierten Phenolnovolaken zu blockieren. Das Ausmaß der Blockierung ist sowohl von der Basizität der Amine, die mit der beschleunigenden Wirkung korreliert, als auch von der Acidität und dem strukturellen Aufbau der modifizierten Phenole abhängig. Die Bewertung der Härtungseigenschaften erfolgte über Gelzeitbestimmungen und Viskositätsmessungen.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 48
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Bruchzähigkeit von Phenolphthalein-Poly(etherketon) bei 190°C wurde mit zwei verschiedenen Methoden bestimmt, der konventionellen Rißwachstumsmethode und der „stress whitening zone“-Methode. Die gute Übereinstimmung der Ergebnisse zeigt, daß letztere Methode zur Bestimmung der Rißinitiierung einiger Polymerer herangezogen werden kann, für die das „blunting line concept“ nicht geeeignet ist.
    Notizen: Fracture toughness values of phenolphthalein poly(ether ketone) (PEK-C) at 190°C were determined by two different methods, i.e. the conventional crack growth method and the crack stress whitening zone method, which show consistent results. This indicates that the crack stress whitening zone method can be used to determine the crack initiation of some polymers for which the blunting line concept is unsuitable.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 49
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 13-22 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Stabilitätskonstanten und zugehörige thermodynamische Parameter (ΔH°, ΔS°) eines intermakromolekularen Komplexes aus Poly(acrylsäure-co-acrylamid), Poly(methacrylsäure-co-acrylamide) und Poly(N-vinylpyrrolidon) wurden mit bekannten Methoden bei verschiedenen Temperaturen bestimmt. Dabei wurde eine stufenweise Auflösung des Komplexes in Abhängigkeit von der Temperatur beobachtet, die mit den Stabilitätskonstanten und den thermodynamischen Parametern korreliert wurde.
    Notizen: Stability constant and related thermodynamic parameters (ΔH° and ΔS°) of a multicomponent intermacromolecular complex consisting of poly(acrylic acid-coacrylamide), poly(methacrylic acid-co-acrylamide) and poly(N-vinylpyrrolidone) have been determined using known methods. A distinct stepwise disintegration of the complex at different temperatures has been observed, and this could be correlated with the stability constant and thermodynamic parameters calculated at various temperatures.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 50
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 53-57 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der Einfluß von Ultraschall auf die Polymerisation und Depolymerisation von Ethylmethacrylat und der Mechanismus des Kettenabbruchs wurden untersucht. Der Polymerisationsumsatz war unabhängig von den verwendeten Ultraschallbedingungen (800 W, 35 kHz). Depolymerisationsversuche mit Ultraschall bei 20°C zeigten, daß Kettenabbruch im wesentlichen durch Disproportionierung stattfindet; dabei werden Molekulargewichte nicht unter ca. 500000 erreicht.
    Notizen: The effect of ultrasound in ethyl methacrylate polymerization and depolymerization and the chain termination mechanism for ethyl methacrylate have been studied. Polymerization conversion at 60°C did not depend on energy (80 W) and frequency (35 kHz) of ultrasound applied. In ultrasound depolymerization studies at 20°C the governing termination mechanism was found to be disproportionation and the lower limiting molecular weight was Mn = 500 000.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 51
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 71-87 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The copolymerization of acrylonitrile with maleic anhydride was investigated to synthesize acylic reactive polymers for manufacture of membranes that serve as support for covalent enzyme immobilization. The free-radical copolymer synthesis was carried out in solution (N,N-dimethylformamide (DMF), dimethylacetamide (DMAC), γ-butyrolactone, ethylene carbonate), by precipitation polymerization (dioxane) as well as bulk polymerization. The polymers were characterized using IR spectroscopy, elementary analysis, NMR spectroscopy, gel permeation chromatography, viscosity measurements, osmometry and potentiometry.The kinetic parameters were followed by dilatometric measurements up to high conversions. The anhydride content in the monomer mixtures showed a significant influence on the rate of polymerization and the molecular weight. With raised concentration of anhydride the polymerization rate and molecular weights decreased. Film forming polymers (M̄η 〉 30 000 g/mol) can be obtained by all copolymerization procedures with exception of solution polymerization in DMF and DMAC, respectively. The content of maleic anhydride in the membrane polymers did not exceed 5 mol-%, even though the maleic anhydride content in the monomer mixtures was raised up to the equimolar mixture. Nevertheless, such low maleic anhydride content of prepared membranes is enough for successful enzyme immobilization with amyloglucosidase (copolymer was prepared in γ-butyrolactone, M̄η = 49 000 g/mol, cPMSA = 0,3 mol-%).
    Notizen: Die Copolymerisation des Acrylnitrils mit Maleinsäureanhydrid (MSA) wurde mit dem Ziel untersucht, acylfunktionalisierte Reaktivpolymere mit Filmbildungseigenschaften herzustellen, um diese in der Anwendung als Membran für kovalente Enzymfixierungen zu nutzen. Die radikalinitiierte Synthese der Copolymeren wurde in Lösung (Dimethylformamid (DMF), Dimethylacetamid (DMAC), γ-Butyrolacton, Ethylencarbonat), durch Fällungscopolymerisation (Dioxan) sowie in Substanz durchgeführt.Die Polymercharakterisierung erfolgte durch IR-Spektroskopie, Elementaranalyse, Kernresonanzspektroskopie, Gelpermeationschromatographie, Viskosimetrie, Osmometrie und Potentiometrie.Die Kinetik wurde durch dilatometrische Untersuchungen bis zu hohen Umsätzen verfolgt. Danach weist der Anhydridgehalt im Monomergemisch einen signifikanten Einfluß auf die Bruttopolymerisationsgeschwindigkeit und die Molmasse der Polymeren auf. Mit steigendem Anhydridanteil wird die Bruttopolymerisationsgeschwindigkeit herabgesetzt und eine Verringerung der Molmasse herbeigeführt. Die Copolymerisation von Acrylnitril und Maleinsäureanhydrid führt mit Ausnahme der Lösungspolymerisation in DMF bzw. DMAC zu Polymeren mit Molmassen oberhalb 30 000 g/mol, was ihre Anwendung als Membran ermöglicht. Die Einbaurate an Maleinsäureanhydrid in den Membranpolymeren ist bis einschließlich einer äquimolaren Zusammensetzung des Monomergemischs nicht größer als 5 mol-%. Derartig niedrige MSA-Reaktivgruppenanteile erweisen sich jedoch als ausreichend, um an einer aus einem Lösungspolymerisat (γ-Butyrolacton, M̄η = 49 000 g/mol, cPMSA = 0,3 mol-%) formierten Membran eine Enzymimmobilisierung mit Amyloglucosidase nachzuweisen.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 52
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 143-160 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Synthesen einer Aryl-alkyl-azodiisocyanat-Verbindung und einer Azoharnstoff-Modellsubstanz werden beschrieben. Aus dem Azodiisocyanat wurden durch Grenzflächen-Polyaddition neuartige Azoharnstoff-Polymer hergestellt. Die zahlenmittleren Molekulargewichte, bestimmt mit der Gelpermeationschromatographie (GPC), lagen zwischen 6000 und 9000. Die Photolyse- und Thermolysereaktionen der Modellsubstanzen und der Polymeren wurden mittels UV-Spektroskopie und Differentialkalorimetrie (DSC) verfolgt und mit den Ergebnissen von ähnlichen Azoamiden verglichen. Der photochemische Polymerabbau wurde mittels GPC untersucht.
    Notizen: The synthesis of an aryl alkyl azo diisocyanate and a model azo urea is described. From the azo diisocyanate new azo polyureas were created by interfacial polyaddition. Molecular weights Mn in the range of 6000 to 9000 were determined by gel permeation chromatography (GPC). Photolysis and thermolysis of both, model compounds and polymers, were studied by UV-spectroscopy and differential scanning calorimetry (DSC), respectively, and the results were compared with those of similar azo amides. Photochemical polymer degradation was followed by GPC.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 53
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 219-219 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 54
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 69-85 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Thermotrop flüssigkristalline Copolyester aus Vanillinsäure (V), 4-Hydroxybenzoesäure (B) und Polyethylenterephthalat (E) wurden mittels 1H-NMR-Spektroskopie und Gelpermeationschromatographie (GPC) untersucht. Die neun möglichen Diaden konnten detektiert und zugeordnet werden. Die Abfolge der Grundeinheiten der V/B/E-Copolyester ändert sich mit zunehmendem B-Anteil von statistischer Verteilung zur Blockbildung und ist außerdem geringfügig von der Katalysatorkonzentration und der Polykondensationsdauer abhängig. Die GPC-Ergebnisse deuten darauf hin, daß die V/B/E-Copolyester engere Molekulargewichtsverteilungen aufweisen als die B/E-Copolyester. Mit von 0 bis 5 mol-% steigendem V-Anteil verengt sich die Molekulargewichtsverteilung. Die Gelpermeationschromatogramme der meisten V/B/E-Copolyester weisen im Unterschied zu den Einzelsignalen der B/E-Copolyester Dublett-Peaks auf.
    Notizen: Thermotropic liquid-crystalline copolyesters made from vanillic acid (V), 4-hydroxybenzoic acid (B) and poly(ethylene terephthalate) (E) were examined by 1H-NMR and GPC investigations. Nine possible diads could be identified and assigned. The sequence distribution of V/B/E copolyesters tends to change from random to block with an increase of B content in the copolyesters. The sequence distribution also varies slightly with catalyst concentration and polycondensation time. GPC results suggest that the V/B/E copolyesters have narrower molecular weight distribution (MWD) than B/E copolyesters. The MWD of the copolyesters narrows gradually with increasing V content from zero to 5 mol-%. The GPC chromatograms of the most V/B/E copolyesters show double peaks, which is different from the single peak of the GPC chromatograms of the B/E copolyesters.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 55
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 111-120 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Strahlungsbeständigkeit von vorbestrahltem Polypropylen mit 2,5 Gew.-% Ethylenanteil wurde mitr einem Copolymeren aus Polypropylen und einem nukleierenden Agens im Hinblick auf die Strahlungssterilisation von medizinischen Geräten verglichen. Die Transparenz des Propylen-Ethylen-Copolymeren wurde durch die Vorbehandlung verbessert. Im Vergleich mit der ebenfalls verbesserten Transparenz des Copolymeren aus Polypropylen und dem nukleierenden Agens wurde durch die Vorbestrahlung die Strahlungsbeständigkeit während der Bestrahlung und bei der Lagerung des bestrahlten Materials verbessert. Dies wird auf die geringere Kristallinität des vorbestrahlten Polypropylens aufgrund von bei der Bestrahlung gebildeten Verzweigungen zurückgeführt.
    Notizen: The radiation stability of the pre-irradiated copolymer of polypropylene containing 2.5 wt.-% ethylene units is compared with a copolymer of polypropylene with a nucleating agent with regard to radiation sterilization of medical devices. It is found that transparency property of the propylene-ethylene copolymer is improved through pre-irradiation processes. This finding was compared with the co-polypropylene with nucleating agent which also gives a better transparency property. In comparison, it is found that pre-irradiated copolymer exhibits better radiation stability during irradiation and during storage after irradiation. The radiation stability of the pre-irradiated copolymer is due to its lower crystallinity caused by the formation of branches during the pre-irradiation process.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 56
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 193-193 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 57
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Polydiaryldiazosulfide wurden durch Grenzflächenpolykondensation aus aromatischen Bisdiazoniumionen und Benzol-1,3-dithiol erhalten. Auf diese Weise wurden Molekulargewichte Mn von 3400 bis 11700 erreicht (GPC).Die neue Polymerklasse zeichnet sich durch hohe Photolabilität und relativ geringe Thermostabilität aus. Mittels UV-Spektroskopie wurde die Photolyse von Modellver-bindungen und Polymeren verfolgt, wobei in nahezu allen Fällen ein Zerfall 1. Ordnung beobachtet wurde. Der photochemische Kettenabbau konnte durch GPC-Untersuchungen verfolgt werden. Die thermische Stabilität der polymeren Diazosulfide wurde durch DSC-Messungen untersucht.
    Notizen: Poly(diaryl diazosulfide)s were synthesized from aromatic bisdiazonium ions and benzene-1,3-dithiol via interfacial polycondensation. Number-average molecular weights Mn in the range of 3400 to 11700 were determined by gel permeation chromatography (GPC).The new polymer class is distinguished by high photosensitivity and low thermostability. First order kinetics during photolysis of nearly all polymers and model compounds under investigation was observed by means of UV spectroscopy. Polymer degradation upon irradiation was verified by GPC measurements. Thermal decay was followed by differential scanning calorimetry (DSC).
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 58
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 228 (1995), S. 161-178 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Three different titration methods were proved with respect to accuracy, reproducibility and handling for the determination of maleic anhydride (MSA) content in acrylonitrile (AN) copolymers in form of poly(AN-co-MSA) and poly(AN-co-styrene-co-MSA). The comparison comprises (i) the combined method A/H characterized by the reaction of anhydride groups (AG) with aniline and titration of the formed monoacid with methanolic KOH (A) and the complete hydrolysis of AG and titration of acid groups (SG) with aqueous NaOH (H), (ii) method B based on the conversion of AG with n-butylamine (BA) and back-titration of unreacted amine with HClO4 in glacial acetic acid and (iii) method C consisting of the reaction of AG with p-chloroaniline (pCA) followed by Cl-determination after the Schöniger-decomposition. Whereas all mentioned methods are suitable for the determination of AG in the presence of initial SG, the combination of A/H additionally allows the simultaneous determination of AG and SG. In comparison with the other methods the combination of A/H is to be favoured due to the possibility to obtain additional information about SG and because of the better results in accuracy, reproducibility and handling. By means of FTIR spectroscopy the content of AG and SG was estimated qualitatively and a correlation between the spectroscopic and potentiometric data of AG was discovered.
    Notizen: Zur Bestimmung des Maleinsäreanhydrid(MSA)-Gehaltes in Acrylnitril(AN)-Copolymeren des Typs Poly(AN-co-MSA) bzw. Poly(AN-co-Styrol-co-MSA) wurden drei verschiedene Titrationsmethoden hinsichtlich ihrer Richtigkeit, Reproduzierbarkeit sowie ihres Zeitaufwandes geprüft. Miteinander verglichen wurden (i) eine Methodenkombination A/H bestehend aus dem Teilschritt A, einer Umsetzung der Anhydridgruppen (AG) mit Anilin einschließlich der Titration der Monosäuregruppen mit methanolischer KOH, und dem Teilschritt H, einer vollständigen Hydrolyse der AG und Titration der Säuregruppen (SG) mit wäßriger NaOH, (ii) Methode B basierend auf der Reaktion der AG mit n-Butylamin (BA) und der Rücktitration des nicht umgesetzten Amins mit Perchlorsäure (HClO4) in Eisessig und (iii) Methode C, beruhend auf der Umsetzung der AG mit p-Chloranilin (pCA) und nachfolgender Chlorbestimmung durch Schöniger-Aufschluß. Während sich alle genannten Methoden prinzipiell für die AG-Bestimmung in Gegenwart initialer SG empfehlen, ist darüber hinaus über A/H eine simultane Bestimmung von AG und SG möglich. Wegen dieses zusätzlichen Informationsgewinns, ihrer besseren Reproduzierbarkeit, der erhöhten Richtigkeit sowie des geringeren zeitlichen und apparativen Aufwandes ist die Kombination A/H zu favorisieren. Mit Hilfe der FTIR-Spektroskopie wurde der Gehalt an AG und SG qualitativ verfolgt und eine Korrelation zwischen den Bandenintensitäten der AG und den potentiometrisch erhaltenen Werten gefunden.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 59
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 15-27 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Härtung eines ungesättigten Polyesterharzes mit niedrigem Exotherm-Peak wurde mit der Standardmethodik und der Differential-Kalorimetrie (DSC) untersucht. Ein Kupfersalz und α-Methylstyrol wurden als Polymerisationsverzögerer benutzt. Der Einfluß der Verzögerer auf die Temperatur des exothermen Peaks, die Gelzeit, die Härtungsenthalpie und die Polymerisationskinetik wurden untersucht.
    Notizen: The curing behavior of an unsaturated polyester resin with low exotherm peak was studied by a standard procedure and by differential scanning calorimetry (DSC). A copper salt and α-methylstyrene were used as the polymerization retarders. The influence of the retarders on the exotherm peak temperature, gelation time, exothermic heat and the polymerization kinetics was investigated.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 60
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 93-112 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Propen und 1-Octen wurden mit dem syndiospezifischen Metallocen-Katalysator Me2C(Cp)(Flu)ZrCl2/MAO copolymerisiert. Es wurde ein hoher, statistischer Octeneinbau beobachtet. Niedrige Octenkonzentrationen beeinflußten die Aktivität des Katalysators nur wenig; Molekulargewicht, Kristallinität, E-Modul und Glastemperatur wurden dagegen mit ansteigendem Octengehalt erniedrigt. Blends aus ataktischem Oligopropen und syndiotaktischem Polypropen bzw. Poly(propen-co-octen) wurden aus einer Toluol-Lösung hergestellt. Diese Lösungsblends wurden mit einem Reaktorblend verglichen, der mit einem Hybrid-Katalysator bestehend aus einer Mischung von syndiospezifischem Me2C(Cp)(Flu)ZrCl2/MAO und unspezifischem Cp2ZrCl2/MAO hergestellt wurde. Das ataktische Oligopropen wirkte als Weichmacher, der E-Modul und Glastemperatur der Blends erniedrigte.
    Notizen: Propene and 1-octene were copolymerized with the syndiospecific homogeneous metallocene catalyst Me2C(Cp)(Flu)ZrCl2/MAO. Large amounts of octene were incorporated randomly. While catalyst activity was not affected markedly by low octene content, molecular weight, crystallinity, Young's modulus, and glass transition temperature were reduced with increasing octene content. Blends of atactic oligopropene with syndiotactic polypropene and poly(propene-co-octene) were prepared from toluene solution and compared with a reactor blend prepared with a hybrid catalyst containing a mixture of syndiospecific Me2C(Cp)(Flu)ZrCl2/MAO and non-specific Cp2ZrCl2/MAO. Atactic oligopropene acted as plasticizer reducing Young's modulus and glass transition temperature of the blends.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 61
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 175-184 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die innere Oberfläche und das Hohlraumsystem von verschiedenartigen Celluloseregeneratfasern werden mit Röntgenkleinwinkelstreuung untersucht. Dabei wird gefunden, daß alle Fasern ein Hohlraumsystem von 0,01 bis 0,1% (Volumenanteil 10-4-10-3) aufweisen. Es zeigt sich jedoch, daß die Größe des Hohlraumsystems für die mechanischen Eigenschaften wenig Bedeutung hat. Es ist vielmehr die Gestalt der Hohlräume und ihre Orientierung, die hier wesentlich sind. Es wird gefunden, daß langgestreckte Hohlräume, vermutlich orientiert, für gute mechanische Eigenschaften verantwortlich sind. Damit können auch verbesserte textile Eigenschaften von Lyocellfasern des NMMO-Typs erklärt werden.
    Notizen: Both the inner surface and the void system of different cellulose regenerate fibers are investigated with X-ray small angle scattering. Thereby it turns out that all fibers have a void system of 0.01 to 0.1% (volume fraction 10-4-10-3). However, the amount of the void system has little influence on the mechanical properties. Rather, it is the shape of the voids and their orientation which proves essential. It is found that elongated voids, probably well oriented, are responsible for superior mechanical properties. This explains also improved textile properties of lyocell fibers of the NMMO type.
    Zusätzliches Material: 6 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 62
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 230 (1995), S. 1-12 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die mit γ-Strahlen induzierte Polymerisation von Methacrylsäure (MA) und Acrylsäure (AA) mit Acrylamid (AAm) (M2) in Substanz wurde untersucht. Die nach Kelen-Tüdős berechneten Copolymerisationsparameter betragen r1 = 1.35 und r2 = 0.22 für MA-AAm bzw. r1 = 1.75 und r2 = 0.10 für AA-AAm. Die Polymerisationsgeschwindigkeit hängt sowohl von der Temperatur als auch von der Comonomerzusammensetzung ab. Die differentialkinetischen Kurven sind unimodal, was darauf hinweist, daß nur der Copolymerisationsprozeß abläuft. Ein zweites Maximum in diesen Kurven wird mit Vernetzung und der Bildung wasserunlöslicher Bestandteile erklärt. Die Copolymeren sind weiße Pulver; die wasserlöslichen Fraktionen sind im Gegensatz zu den wasserunlöslichen nicht giftig, aber als Immunmodulatoren weniger aktiv.
    Notizen: A study was made of the γ-radiation-induced bulk copolymerization of the methacrylic acid-acrylamide (M2) (MA-AAm) and acrylic acid-acrylamide (M2) (AA-AAm) monomeric pairs. The copolymerization reactivity ratios deterined according to the Kelen-Tüdő method were: r1 = 1.35, r2 = 0.22 for the MA-AAm pair, and r1 = 1.75, r2 = 0.10 for the AA-AAm pair. It has been established that the polymerization rate depends both on the composition of the starting reaction mixture and on the reaction temperature. The differential kinetic curves obtained are unimodal ones, suggesting the occurrence of only one process, i.e. copolymerization. A second maximum in these curves, appearing at elevated temperature, is explained by crosslinking and formation of a water-insoluble fraction. The copolymers obtained are white powders; in contrast to their water-insoluble fractions, the water-soluble ones are not toxic but they are less active as immunomodulators.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 63
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 228 (1995), S. 201-219 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Hydrolyse von Poly(ester-urethan-harnstoffen) (PURUs) wurde untersucht. Es handelt sich dabei um einen komplexen Vorgang, der die Analyse der Beziehung zwischen der Zusammensetzung der PURUs und ihrer Hydrolysebeständigkeit erschwert. Es wurde gefunden, daß die Hydrolysebeständigkeit mit Zunahme (i) der Polyol-Acidität, (ii) des Estergruppen-Gehaltes, (iii) der Beweglichkeit der Hauptketten und (iv) deren Hydrophilie abnimmt; die Molmasse des Polyols scheint keinen merklichen Einfluß darauf zu haben. Der negative Einfluß von Ethergruppen (obwohl hydrolysebeständiger als Estergruppen) ist möglicherweise auf eine Zunahme der Hauptkettenbeweglichkeit und den dadurch leichteren Zugang von Wassermolekülen zu Estergruppen zurückzuführen. Der positive Effekt von aromatischen Ringen in Polyolen kann einer erhöhten Steifigkeit der Hauptkette als auch einer ansteigenden Hydrolysebeständig-keit benachbarter Estergruppen durch Resonanzeffekte zugeschrieben werden. Insgesamt kann angenommen werden, daß die beschriebenen Effekte sich überlagern und gleichzeitig die resultierende Hydrolysebeständigkeit vorherbestimmen. Es sollte daher möglich sein, qualitative Vorhersagen bezüglich der Hydrolysebeständigkeit in Abhängigkeit von der Zusammensetzung der PURUs zu treffen.
    Notizen: Hydrolysis of poly(ester urethane ureas) (PURUs) is a complex phenomenon which impedes the analysis of the relationships between their composition and hydrolytic stability. Hydrolytic stability of PURUs decreases due to rising (i) polyol acidity, (ii) content of ester groups, (iii) flexibility and (iv) hydrophilicity of the backbones; molar mass of polyols does not seem to have any appreciable effect on it. Negative influence of ether groups (which have better hydrolytic stability than ester groups) is probably linked to the increase in the backbone flexibility and, consequently, to easier access of water molecules to ester groups. Positive effect of aromatic rings in polyols can be ascribed to enhanced rigidity of the backbones as well as to increased hydrolytic stability of adjacent ester groups due to the resonance effect. It can be presumed that the mentioned effects will superpose and simultaneously predestine the resulting hydrolytic resistance. Considering the observed tendencies, it is possible to qualitatively predict the trends how the hydrolytic stability will respond to changes in PURUs composition.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 64
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 63-72 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Eine neuartige lichtempfindliche Naphthochinondiazid-Verbindung (NQD) wurde aus 2,6-Bis(hydroxymethyl)-3,4-dimethylphenol und Toluoldiisocyanat synthetisiert und mit IR-, NMR- und Elementaranalyse identifiziert. Die Bleicheigenschaften unter Lichteinwirkung wurden mit UV-Spektrophotometrie bestimmt. Die Anwendung von NQD in der Photolithographie als positiver Photoresist sowie einer wäßrigen Lösung von NQD, Novolak, Cellosolve-Acetat und DMF als lichtempfindliches Material wurde untersucht. Das hergestellte NQD erwies sich als effektive Komponente in positiven Photoresists. Die optimalen Bedingungen der UV-Dosis, Schichtdicke und Resistzusammensetzung wurden abgeschätzt. Die Auflösung des positiven Photoresists wurde durch Rasterelektronenmikroskopie bestimmt. Außerdem wurde der Einfluß von UV-Dosis und -Wellenlänge, Einwirkungsdauer und Entwicklungszeit auf die Empfindlichkeit und die Auflösung des Photoresists untersucht.
    Notizen: A new photosensitive naphthoquinonediazide (NQD) was synthesized from 2,6-bis-(hydroxymethyl)-3,4-dimethylphenol and toluene diisocyante. NQD was identified by using IR, NMR and elemental analyses. Photobleachable characteristics were evaluated by UV spectrophotometry. Applications of the NQD on the photolithography as a positive working photoresist were investigated. The aqueous solution of NQD, novolak, cellosolve acetate, and DMF was used as a photosensitive material. It was found that NQD synthesized in this investigation can be used as an effective component in a positive photoresist. Optimal conditions of the UV dose, coating thickness, and development of the resist system were estimated. Resolution of the positive resist was evaluated by SEM technique. Effects of UV dose, exposure time, development time, and exposure UV wave length on the sensitivity and resolution of the photoresist were investigated.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 65
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 123-132 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die radikalinduzierte Polymerisation von phenlysubstituierten 2-Methylen-1,3-dioxanen wurde untersucht. Es kann gezeigt werden, daß die grundlegende Polymerisationstendenz derartiger Ketenacetale darin besteht, über die Doppelbindung zu hochmolekularen Polyacetalen ohne eine nennenswerte Ringöffnung zu polymerisieren. Einflußfaktoren, wie z. B. resonanzstabilisierte Kettenenden oder sterische Hinderungen während des Wachstumsschrittes sind nicht in der Lage, die Polymerisation in die Richtung der gewünschten Ringöffnung zu lenken.Mittels Dichtemessungen wurden Informationen über das Schrumpfungsverhalten gewonnen. Es konnte gezeigt werden, daß raumerfüllende Substituenten am 2-Methylen-1,3-dioxansystem bei der Homopolymerisation grundsätzlich eine geringe Volumenschrumpfung bewirken und die Schrumpfung von herkömmlichen Monomeren bei der Copolymerisation herabsetzen können.
    Notizen: We have investigated the free radical polymerization of phenyl-substituted 2-methylene-1,3-dioxanes. It was shown that there is a basic tendency of such ketenacetals to undergo exclusively a vinyl polymerization forming high-molecular polyacetals without any detectable ring opening. The polymerization with the desirable ring opening reaction cannot be controlled by factors like resonance stabilized chain ends or steric hindrance in the growing step.From densitometric measurements we got new information about the shrinkage behaviour. It was demonstrated that bulky substituents attached to the 2-methylene-1,3-dioxane system result in a significant low shrinkage in homopolymerization and the shrinkage of common comonomers can be decreased by copolymerization.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 66
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 133-143 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Polymerisation von Acrylamid (AAM) in einer konzentrierten bikontinuierlichen Mikroemulsion wurde studiert. Die Initiierungsstelle bei Verwendung von radikalischen Initiatoren mit verschiedener Wasserlöslichkeit wurde untersucht. Es wurde festgestellt, daß ein vollständig oder teilweise wasserlöslicher radikalischer Initiator die Acrylamidpolymerisation in der untersuchten Mikroemulsion effektiv initiieren kann. Die dadurch entstandenen Polymeren weisen eine Spezialstruktur auf, die von der Zusammensetzung der ursprünglichen Mikroemulsion abhängig ist.
    Notizen: The polymerization of acrylamide (AAM) in concentrated bicontinuous microemulsion systems was studied. The locus of initiation using radical initiators with various water-solubility was investigated. It was found that water-soluble and partially water-soluble initiators initiate the AAM polymerization in the reaction systems under investigation very effectively. The polymers thus formed have special structures dependent on the composition of the original concentrated bicontinuous microemulsion.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 209-209 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 68
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 229 (1995), S. 185-198 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Bacteriorhodopsin is a component of the purple membrane of Halobacterium halobium. It shows photochemical activity and undergoes a series of photocyclic-associated conformational changes. Incorporated in a matrix it is suitable as a light energy/electrical current transducer. Very important is an orientation of purple membrane fragments.The reaction between solutions of a polyelectrolyte and multivalent ions leads to a ionotropic gel, that is a gel with an ordered structure. If the gel formation was carried out in the presence of purple membrane fragments, the Bacteriorhodopsin is highly oriented and produces a photoelectrical signal. It consists a correlation between the light direction and the orientation of the purple membrane due to the gel formation.
    Notizen: Bacteriorhodopsin ist Bestandteil der sogenannten Purpurmembran des Mikroorganismus Halobacterium halobium. Es zeigt photochemische Aktivität und kann als biologischer Lichtwandler fungieren. Voraussetzung hierfür ist eine orientierte Anordnung der Purpurmembran in einer Matrix.Das Prinzip der ionotropen Gelbildung, d. h. die geordnete Strukturbildung einer Polyelektrolytlösung infolge eines gerichteten Diffusionsstromes von mehrwertigen Ionen gestattet die orientierte Anordnung der Purpurmembran. Durch Lichteinwirkung werden elektrische Signale induziert. Es besteht ein Zusammenhang zwischen der Richtung des Strahlungseinfalls und der durch die Gelwachstumsrichtung festgelegten Orientierung der Purpurmembran.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 69
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The thermal oxidation of β ray-crosslinked polyethylene (XLPE) was studied in temperatures ranging from 90 to 180°C. Various analytical methods were used for determination of an end of the induction period on bulk samples: gravimetry, ultimate tensile properties, density and color change. On microtome slices of ∼30 μm thickness the depth distribution of oxidation products, phenolic antioxidant, density and tensile ultimate properties were followed as a function of exposure time by respectively IR and UV spectrophotometry, densitometry and Microfoil Tensile Testing.Depending on the testing method different durations of induction period (DIP) were obtained. They increase in following order:Phenol depletion 〈 Ultimate elongation 〈 Density 〈 Carbonyl build-up ≤ Color change 〈 Weight loss.The difference between phenol depletion DIP and carbonyl build-up DIP can be considered as negligible at temperatures higher than the melting point (about 30%) but it reachs more than 100% at T〈 Tm.Different kinetic regimes of phenol consumption were observed depending on the exposure temperature. A mechanistic interpretation is proposed explaining the role of the stabilizer system in initially homogeneous and later heterogeneous oxidation of the bulk material.The Arrhenius law was applied to different durations of induction period. A discontinuity appeared in the melting point region (120-130°C) which is tentatively interpreted in terms of different stabilizer concentration in amorphous phase of semicrystalline material (T 〈 Tm) and in melt material (T 〉 Tm). On the basis of the presented complex study of polyethylene thermo-oxidation, different aspects of lifetime predictions are discussed.
    Zusätzliches Material: 10 Ill.
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  • 70
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Most plastics are produced from oil and have a high potential as hydrocarbon sources for the chemical industry. Pyrolysis is a practicable way to pyrolyze mixed plastics. The fluidized bed pyrolysis has turned out to be particularly advantageous. 25 to 45 percent of product gas with a high heating value and 30 to 50 percent of an oil rich in aromatics, could be recovered. The oil is comparable to that of a mixture of light benzene and bituminous coal tar. Up to 60 percent of ethene and propene are produced by using mixed polyolefins as feedstock. Under appropriate conditions the pyrolysis could be successful on the market.
    Zusätzliches Material: 1 Ill.
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  • 71
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: When poly(methyl methacrylate) films containing UV absorbers are exposed to UV light, the absorbers undergo photodegradation resulting in loss of absorbance. If the data extend for less than one half-life, both zero and first order kinetic treatment give fairly linear fits, but the rate constants so derived are dependent on the initial absorbance of the films. When the zero order rate constants are corrected to account for the higher rate of degradation near the surface compared with the bulk that occurs in highly absorbing films, consistent “infinite absorption” zero order rate constants are derived. The inhomogeneous degradation is due to only the highly absorbed, higher energy light contributing significantly to the degradation. For the benzophenone and benzotriazole classes of absorber, at least 65% of the degradation is due to light with wavelengths 〈 350 nm. Structural variations generally caused only small differences in the rates of degradation of these classes of absorbers unless the substitutions disrupted the intramolecular hydrogen bonds that are critical for stability. If the hydrogen bond is weakened, the absorber is less stable.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 72
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Aus Cardanol, einem Bestandteil der Schale der Cashewnuß, wurde durch Kondensation mit Formaldehyd und substituierten aromatischen Verbindungen unter saurer oder basischer Katalyse eine Reihe von Harzen hergestellt und anhand ihrer IR-Spektren charakterisiert. Sie lassen sich als selektive Ionenaustauscher für bestimmte Ionen verwenden, was mittels einer Gleichgewichtsmethode geprüft wurde. Das thermische Verhalten der Harze wurde untersucht, und ein plausibler Abbaumechanismus wird vorgeschlagen.
    Notizen: A large number of resins have been synthesized by reacting cardanol, a constituent of cashewnut shell liquid, with formaldehyde and substituted aromatic compounds in the presence of acidic and basic catalysts. The resins have been characterized by IR spectra. They were shown to be selective ion exchangers for certain metal ions. A batch equilibrium method was used for studying the selectivity of the metal ions. The thermal behaviour of the resins has been studied and a plausible degradation mechanism has been suggested.
    Zusätzliches Material: 3 Ill.
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  • 73
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Bisphenol A polycarbonate (BPA-PC) is an important high performance engineering thermoplastic well known for its outstanding combination of toughness, transparency and heat resistance. These properties make it an idel material for demanding applications where it is exposed to external stresses such as elevated temperatures, ultraviolet light and γ-ray sterilization. However, on extended exposure to these conditions, BPA-PC slowly degrades, turning progressively more yellow, eventually leading to a decrease in its physical properties. Over the years, there has been numerous studies made to understand these degradative processes so as to better design more stable BPA-PC formulations. In this paper, this chemistry is briefly reviewed along with more recent work in this area with a special emphasis on the efforts made to identifying the actual chemical species responsible for the observed yellow color and the chemistry responsible for their formation.
    Zusätzliches Material: 7 Ill.
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  • 74
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Hindered Amine Light Stabilizers (HALS) are know to inhibit the photo-oxidation of polymers. A key reaction in their stabilization mechanism is believed to be the conversion of a hindered aminoether into a nitroxyl radical. Several different possible mechanisms for this conversion were explored. One, the elimination of the aminoether to form an olefin and hydroxylamine (an intermediate in the formation of a nitroxyl), while possible at high temperatures, cannot account for the inhibitory activity we observed for secondary and primary aminoethers. Direct radical displacement by peroxy radicals was also considered. However, the products predicted by this reaction pathway were not observed. Finally, oxidation of the nitrogen by a peroxy radical, by either electron transfer or a radical attack on the nitrogen, was investigated. While electron transfer was shown to be unlikely, direct oxidation of the aminoether nitrogen was supported by our results. A detailed mechanism for the reaction of both alkyl- and acyl-peroxy radicals with aminoethers is proposed.
    Zusätzliches Material: 2 Ill.
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  • 75
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die thermischen und dynamisch-mechanischen Eigenschaften einiger linearer kautschukelastischer Polyurethane mit chemisch unterschiedlichen starren Segmenten wurden untersucht und zur chemischen Zusammensetzung in Beziehung gesetzt. Interessante Zusammenhänge wurden zwischen der Kristallinität der elastischen Polyurethanharnstoffe und der aromatischen oder cycloaliphatischen Natur der Diisocyanat-Komponenten gefunden. Darüber hinaus scheinen die Ergebnisse bei einem bestimmten Verhältnis zwischen starren und flexiblen Segmenten und bei gegebener Zusammensetzung der flexiblen Gruppen auf eine bessere Phasenseparation bei den Polyurethanharnstoffen mit cycloaliphatischen starren Segmenten als bei solchen mit aromatischen, starren Einheiten hinzuweisen.
    Notizen: Experimental batches of linear rubber-like polyurethanes characterized by the presence of chemically different hard segments are studied and their thermal and dynamic-mechanical properties are related to the differences in chemical compositions. Interesting correlations are found between the development of crystallinity in such elastomeric poly(urethaneurea)s and the aromatic or alicyclic nature of the diisocyanate. Moreover, for a fixed ratio between hard and soft segments, and for a given composition of the soft segment, the results seem to indicate a better degree of phase separation in cycloaliphatic-based hard segment poly(urethaneurea)s than in aromatic-based hard segment poly(urethaneurea)s.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 76
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 135-144 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Makromonomere Polyethylenoxid-Azoinitiatoren (Makroinimere) MIM-400 und MIM-1500 wurden synthetisiert und IR- und NMR-spektroskopisch sowie mit Hilfe der DSC-Analyse charakterisiert. Die mit diesen Makroinimeren initiierte Dispersions-polymerisation von Styrol bzw. Methylmethacrylat (MMA) in Ethanol/Wasser bei 60°C wurde untersucht. Dabei wurde gefunden, daß die Polymerisationsgeschwindig-keit mit zunehmender MIM-Konzentration ansteigt, wobei der Anstieg im Styrolsystem ausgeprägter war. Im Bereich von mittleren Umsätzen konnte gezeigt werden, daß die Polymerisationsgeschwindigkeit von MMA proportional der Potenz 1,7 bzw. 1,6 von [MIM-400] bzw. [MIM-1500] ist, während für Styrol eine Potenz von 2,5 bezüglich [MIM-400] gefunden wurde.
    Notizen: Macromonomeric poly(oxyethylene) azoinitiators (macroinimers) MIM-400 and MIM-1500 were synthesized and characterized by IR and NMR spectroscopy and DSC techniques. The dispersion polymerizations of styrene and methyl methacrylate (MMA) initiated by poly(oxyethylene) macroinimers (MIM-400 and MIM-1500) in water/ethanol were investigated at 60°C. The rate of polymerization was found to increase with increasing concentration of MIM and the increase was more pronounced in the styrene system. In the range of medium conversions the rate of polymerization was found to be proportional to the 1.7th and 1.6th power of [MIM-400] and [MIM-1500] for MMA and to the 2.5th power of [MIM-400] for styrene, respectively.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 77
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 231 (1995), S. 187-198 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Glass transition temperatures of binary and ternary blends of chemically uniform poly(styrene-co-n-butyl methacrylate)s with a mean content of 30.8 wt.-% of n-butyl methacrylate and number-average molar masses in the range of 4900 and 67000 g/mol have been investigated in relation to their composition. The blends showed significant deviations from an ideal behaviour with reference to a linearity between glass transition temperature and composition.This phenomenon is described by a mathematical model where polynoms are particularly well suited to represent the glass transition temperatures of the blends, partly exceeding those of the pure components. Finally, various reasons of these deviations were discussed. Here, energetical interactions seem to be of considerable importance combined with a nonadditivity of volumes.
    Notizen: Die Glasübergangstemperaturen binärer und ternärer Mischungen chemisch einheitlicher Poly(styrol-co-n-butylmethacrylat)e mit einem mittleren n-Butylmethacrylat-Anteil von 30,8 Gew.-% und unterschiedlichen zahlenmittleren Molmassen im Bereich von 4900 bis 67000 g/mol wurden in Abhängigkeit von der Zusammensetzung untersucht. Es wurden wesentliche Abweichungen vom idealen Verhalten bezüglich einer linearen Abhängigkeit zwischen Glasübergangstemperatur und Zusammensetzung festgestellt.Dieses Verhalten konnte mit einem mathematischen Modell dargestellt werden, wobei sich insbesondere Polynome zur Beschreibung der teilweise über den Werten der Ausgangskomponenten liegenden Glasübergangstemperaturen der Mischungen als geeignet erwiesen. Schließlich wurden verschiedene Ursachen für diese Abweichungen diskutiert, wobei offensichtlich energetische Wechselwirkungen verbunden mit einer Nichtadditivität der Volumina von wesentlicher Bedeutung sind.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 78
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 233 (1995), S. 133-148 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: ε-Caprolactam (CL) and phenyl glycidyl ether (PGE) were homopolymerized using the initiator/accelerator-systems Na-caprolactam/N-acetyl-caprolactam (NaCL/AcCL) and Na-caprolactam/N-acetyl imidazole (NaCL/AcImi). In a one-pot reaction both monomers gave different oligomeric reaction products depending on the reaction temperature (100°C to 140°C, max. 240°C) but no regular copolymers. Soluble products were separated by HPLC and identified by means of spectroscopic methods. In acetone insoluble products were investigated by IR- and NMR-spectroscopy, mass spectrometry and elemental analysis.
    Notizen: Es wurden Versuche zur Homopolymerisation von ε-Caprolactam (CL) und Phenylglycidether (PGE) mit den Initiator/Beschleuniger-Systemen Na-Caprolactam/N-Acetylcaprolactam (NaCL/AcCL) und Na-Caprolactam/N-Acetylimidazol (NaCL/AcImi) durchgeführt, um die für eine mögliche Copolymerisation von CL und PGE geeigneten Reaktionsbedingungen zu ermitteln. CL und PGE wurden in unterschiedlichen molaren Verhältnissen (CL : PGE = 1 : 5 bis 1 : 0,05) und bei Temperaturen zwischen 100°C und 140°C (max. 240°C) in einer Eintopfreaktion polymerisiert.Die löslichen Produkte wurden mittels HPLC getrennt und spektroskopisch identifiziert. Die in Aceton unlöslichen Produkte wurden mit IR- und NMR-Spektroskopie, Massenspektrometrie (MS) und Elementaranalyse untersucht.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 79
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 236 (1996), S. 111-127 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Neuartige Fluoropolyether-Polyol-Harze, die mit konventionellen Härtern wie Polyisocyanaten oder Melaminen aushärtbar sind, wurden hergestellt. Zunächst wurden oligomere NCO-terminierte Prepolymere durch Addition von Fluorpolyether-Makrodiolen unterschiedlicher Molekulargewichte an Isophorondiisocyanate erhalten. Durch die Reaktion dieser Prepolymeren mit Trimethylolpropan wurden endständige Hydroxygruppen eingeführt. Die Viskosität von Lösungen dieser Harze wurde bei unterschiedlichen Konzentrationen (Massenbruch 0,4-0,8) und Temperaturen (25°C-65°C) gemessen. Die erhaltenen Werte wurden auf der Basis der Erickson-Gleichung (Konzentrationsabhängigkeit von η) und unter Berücksichtigung des WLF-und des Arrhenius-Modells (Temperaturabhängigkeit von η) diskutiert. Das thermische Verhalten der Harze und von ausgehärteten Filmen wurde mit DSC bestimmt. Dabei wurden zwei Glasübergange beobachtet, die den separierten fluorhaltigen und nicht-fluorhaltigen Phasen zugeordnet werden können. Die Analyse des Zugverhaltens der Filme zeigte besonders bei den mit Isocyanat gehärteten Proben ein ausgeprägtes hart-plastisches Verhalten. Diese Werkstoffe erscheinen für die Anwendung als hoch-wertige, dauerfeste und klare Beschichtungen geeignet.
    Notizen: New fluoropolyether polyolic resins are presented suitable to be cured with conventional hardeners as polyisocyanates or melamines. These resins are prepared by addition of fluoropolyether macrodiols (Fomblin® ZDOLTX) of various molecular weights to isophorone diisocyanate (IPDI) to give oligomeric NCO-terminated prepolymers. The final hydroxy functionality is obtained by the reaction of those prepolymers with trimethylolpropane (TMP). The viscosity of the resins is measured at various concentrations (weight fraction 0.8 - 0.4) and temperatures (T = 25-65°C). The results are discussed in terms of the Erickson equation (η vs. concentration) and using the WLF and Arrhenius models (η vs. T). The thermal behavior is studied by DSC for both the resins and cured films indicating the presence of two Tgs, corresponding to the segregated fluorinated and hydrogenated phases, the former particularly evident with the highest molecular weights of the fluorinated macromer. Tensile curves of selfsupported films are then analyzed showing an evident tough-plastic behavior especially for the isocyanate-cured films. The application of such materials as high-durability clear coats is finally proposed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 80
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 237 (1996), S. 1-44 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Zur Verbesserung der Maßhaltigkeit und der Zähigkeit von gehärteten Melamin-Formaldehyd-Harz-Formmassen (MF) wurden teilverträgliche, methylolgruppenhaltige Epoxidharze (EP) auf Bisphenol A-Basis hergestellt und charakterisiert. Die Vernetzung solcher Epoxyresolharze durch 2-Ethyl-4-methylimidazol in Gegenwart von MF-Harz wurde untersucht. Spritzgepreßte Probekörper zeigen eine Zweiphasenstruktur; die EP-Phase kann als Wirt für carboxy-funktionalisierte, oligomere NBR-Kautschuke (CTBNX) dienen, die für sich allein in MF-Harzen nicht wirksam sind. Unter der Voraussetzung von kovalenten Bindungen in der Phasengrenzfläche kann durch den Zusatz von 0,5 bis 4 Gew.-% CTBNX zur MF-Formmasse bei EP-Anteilen bis 20 Gew.-% eine 50 bis 100proz. Steigerung von Bruchdehnung und Schlagzähigkeit erreicht werden, ohne daß Steifigkeit und Wärmeformbeständigkeit wesentlich abfallen. Bei moderaten EP/CTBNX-Gehalten wird zusätzlich die Nachschwindung von MF-Formteilen vermindert.
    Notizen: In order to improve dimension stability and toughness of melamine formaldehyde moulding materials (MF), compatible bisphenol A epoxy resins (EP) with additional methylol groups were synthesized and characterized. Crosslinking of those epoxyresol resins with 2-ethyl-4-methylimidazole in the presence of MF resin was investigated. Transfer-moulded specimens revealed a two-phase morphology in which the EP phase is used as a host for modification with carboxylic functionalized oligomeric NBR rubber (CTBNX), which is not effective in MF moulding materials alone. The addition of 0.5 - 4 wt.-% CTBNX to the MF moulding materials at an epoxy content of maximum 20 wt.-% results in 50-100 % increase of elasticity and toughness without serious decrease in stiffness and heat deflection temperature, provided that covalent interfacial bonds exist. In addition, the post-shrinkage of MF parts decreases if a moderate EP/CTBNX content is introduced.
    Zusätzliches Material: 26 Ill.
    Materialart: Digitale Medien
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  • 81
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 11-30 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Der gleichzeitige Einfluß des Verhältnisses von Fließhilfsmittel (Paraloid K 120N), Rußart und Schlagzähmodifikator (CPE 3615 und Kane Ace B56 A) auf die wichtigsten physiko-mechanischen Eigenschaften unplastifizierter PVC-Mischungen wurde studiert.Die erhaltenen Resultate wurden mathematisch verarbeitet und graphisch als Funktionsflächen dargestellt. Bemerkenswert ist, daß die Einführung von 2,5 und 5 Teilen Ruß eine Verbesserung der physico-mechanischen Eigenschaften ermöglicht. Dieses Resultat ist durch die Anwesenheit der Schlagzäh- und Fließmodifikatoren zu erklären.
    Notizen: The concurrent influence of the processing aid (Paraloid K 120N) and the carbon black ratio, as well as the nature and the ratio of the impact modifier (CPE 3615 and Kane Ace B56 A) on the main physico-mechanical characteristics of the poly(vinyl chloride)-based unplasticized mixtures have been studied. The results obtained, processed mathematically and plotted graphically in the form of response surfaces, evidenced that the improvement of certain physico-mechanical properties becomes possible by the introduction of 2.5 parts and 5.0 parts carbon black into these compounds. This is due to the introduction of impact modifiers and processing aids into the mixtures.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 82
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 63-71 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Eine Reihe neuartiger Polyhydrazide mit endständigen Phenoxygruppen wurde aus äquimolaren Anteilen von Dicarbonsäuredichloriden und Phenoxyterephthalsäuredihydrazid durch Lösungspolykondensation in N-Methyl-2-pyrrolidinon (NMP) bei niedriger Temperatur hergestellt. Durch thermische Cyclisierung der Polyhydrazide wurden die entsprehchenden Poly(1,3,4-oxadiazol)e mit endständigen Phenoxygruppen erhalten. Die Polymeren wurden durch Viskosimetrie, Löslichkeitsuntersuchungen, IR-Spektroskopie, Differentialkalorimetrie und Thermogravimetrie charakterisiert.
    Notizen: A series of new polyhydrazides containing pendent phenoxy groups has been synthesized by low-temperature solution polycondensation of equimolar amounts of diacid dichlorides and 2-phenoxyterephthalic dihydrazide in N-methyl-2-pyrrolidi-none (NMP). The thermal cyclization of the polyhydrazides gave the corresponding poly(1,3,4-oxadiazole)s containing pendent phenoxy groups. The polymers were characterized by viscometry, solubility measurements, IR spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 83
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 105-117 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Ein Ethylen-Vinylacetat-Copolymeres (EVA) mit 12% Vinylacetat-Gehalt wurde mit Trimethylolpropantrimethacrylat (TMPTMA) als Sensibilisator mit Elektronen bestrahlt. Die mechanischen und elektrischen Eigenschaften der bestrahlten Copolymerproben wurden untersucht. Die Resultate zeigen, daß sich Zugfestigkeit und Bruchdehnung zunächst mit zunehmender Strahlungsdosis verbessern und bei Überschreiten einer optimalen Strahlungsdosis und Sensibilisatorkonzentration wieder verschlechtern. Durch die Bestrahlung wird eine Vernetzung des Polymeren ausgelöst, die auf den sich mit der Strahlungsdosis erhöhenden Gelanteil zurückgeführt wird. Im Vergleich mit den Originalproben nehmen sowohl die Dielektrizitätskonstante als auch der dielektrische Verlustfaktor durch die Elektronenbestrahlung ab.
    Notizen: Ethylene-vinyl acetate (EVA) copolymer (12% vinyl acetate content) is subjected to electron beam irradiation using trimethylolpropane trimethacrylate (TMPTMA) as a radiation sensitizer. Mechanical and electrical studies of these irradiated samples show that the strength properties (tensile strength, elongation at break) are increased with radiation dosage up to an optimum radiation dose and sensitizer level above which the properties begin to deteriorate. Crosslinking of the polymer takes place on irradiation which is attributed to an increased gel content with increasing radiation dose. Compared to the original samples both dielectric constant and dielectric loss factor decrease for samples subjected to irradiation.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 84
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 238 (1996), S. 143-163 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Cellulose-p-toluolsulfonsäureester (Cellulosetosylate) lassen sich durch homogene Umsetzung von Cellulose in einer Lösung aus N,N-Dimethylacetamid und LiCl mit Tosylchlorid (Tos-Cl) und Triethylamin in 24 h bei 8°C in hoher Ausbeute und mit minimalem Einbau von Chlordesoxy-Gruppen herstellen. Die unterschiedlichen Celluloseausgangsmaterialien hatten durchschnittliche Polymerisationsgrade von 280 bis 5100. Die Produkte wurden mit Elementaranalyse, 13C-NMR- und FTIR-Spektroskopie und durch Bestimmung der Grenzviskositäten charakterisiert. Die Erhöhung des Molverhältnisses Tos-Cl/Anhydroglucose-Einheit (AGU) von 0.6 auf 9.0 führte zu einem Anstieg des Substitutionsgrades (DS) von 0.4 bis auf einen Maximalwert von 2.3. Die Cellulosetosylate sind in herkömmlichen organischen Lösungsmitteln wie Dimethylsulfoxid (im gesamten DS Bereich) und in N,N-Dimethylacetamid, N,N-Dimethylformamid, Aceton, Tetrahydrofuran und Trichlormethan (in Abhängigkeit von DS) löslich. Durch 13C-NMR-Spektroskopie wurde nachgewiesen, daß die Tosylierung am O-6 Atom der AGU schneller als an den O-2/3 Atomen erfolgt. Die Analyse der korrespondierenden Ioddesoxycellulosen, die durch Umsetzung mit NaI in Acetylaceton synthetisiert wurden, bestätigte dies zusätzlich. Darüber hinaus wurden wichtige Eigenschaften der Cellulosetosylate wie die Stabilität gegenüber Alkali und thermischer Beanspruchung untersucht.
    Notizen: Pure cellulose p-toluenesulfonates (tosylates) with an insignificant formation of chlorodeoxy groups were prepared by reacting cellulose dissolved in a solution of N,N-dimethylacetamide and LiCI with tosylchloride (Tos-CI) in the presence of triethylamine within 24 h at 8°C. Various cellulosic starting materials with a degree of polymerization from 280 to 5 100 were used. The samples obtained were characterized by means of elemental analysis, FTIR and 13C NMR spectroscopy, and their intrinsic viscosities. The rise of the molar ratio of Tos-CI/anhydroglucose unit (AGU) from 0.6 to 9.0 leads to an increase in the degree of substitution (DS) from 0.4 up to a maximum value of 2.3. The cellulose tosylates are readily soluble in common organic solvents like dimethyl sulfoxide (within the whole DS range) and in N,N-dimethylacetamide, N,N-dimethylformamide, acetone, tetrahydrofuran and trichloromethane depending on DS. As revealed by 13C NMR spectroscopy a faster tosylation takes place at the O-6 atom of AGU compared with the O-2/3 atoms. This was additionally confirmed by analysis of the corresponding iododeoxy celluloses synthesized with NaI in acetylacetone. Furthermore, some important properties as stability against alkaline and heat were studied as well.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 85
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 27-32 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Herstellung einer SiC-Oberfläche auf Kohlefasern unter Verwendung einer Sol-Gel-Mischung von Tetraethylorthosilikat (TEOS) und Phenolharz wurde untersucht. FTIR- und SEM-Untersuchungen zeigten, daß die SiC-Oberfläche durch carbothermische Reduktion der Sol-Gel-Mischung bei 1 420°C innerhalb von 15-20 min in einer Argon-Atmosphäre gebildet werden kann. Mittels TGA konnte gezeigt werden, daß die SiC-Beschichtung die thermo-oxidative Stabilität der Kohlefasern erhöht. Bei der erreichten SiC-Schichtdicke von 0,47 μm, bei einem C/Si-Verhältnis von 4, zeigt sich keine Beeinflussung der mechanischen Stabilität der Kohlefasern.
    Notizen: The preparation of a SiC coating on a carbon fiber surface using a sol-gel mixture of tetraethyl orthosilicat (TEOS) and phenolic resin was studied. FTIR and SEM investigations indicated that the SiC coating can be formed by carbothermal reduction of the sol-gel mixture at 1420°C for 15-20 min in an argon atmosphere. TGA of the coated fiber was also performed, showing that the SiC coating improves the thermooxidative stability of the carbon fiber. With the thickness of the obtained coating of 0.47 μm using a C/Si ratio of 4, this treatment does not affect the carbon fiber strength.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 86
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 55-62 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Diese Mitteilung behandelt den Einfluß von oligomeren Polypropylen- und Polybutylenölen mit unterschiedlichem Molekulargewicht auf die adhäsiven Eigenschaften von ataktischem Polypropylen (aPP) und dessen Mischungen mit einem Styrol-Ethylhexylacrylat-Copolymeren. Die mechanische Adhäsionsarbeit Am von Mischungen, die ataktisches Polypropylen und das Oligomere enthalten, steigt mit dem Molekulargewicht des Oligomeren, was im Fall des Propylenöls signifikanter ist. Im Fall der ternären Mischungen des ataktischen Polypropylens mit dem Styrol-Ethylhexylacrylat-Copolymeren und Oligomeren wird ein Adhäsions-Maximum beobachtet, wenn der Gehalt an Styrol-Ethylhexylacrylat-Copolymeren in der Mischung ungefähr 30 Gew.-% erreicht. Wenn kein Oligomeres in der Mischung vorhanden ist, kann man bei dieser Zusammensetzung ein Adhäsions-Minimum beobachten, was auf die Unverträglichkeit der übrigen Komponenten zurückzuführen ist.
    Notizen: This paper deals with the influence of oligomers, namely propylene oil and butylene oil, of different molecular weight on the adhesive properties of atactic polypropylene (aPP) and its mixtures with styrene-2-ethylhexyl acrylate (S-EHA) copolymer. The mechanical work of adhesion Am of the mixture containing atactic polypropylene and oligomer increases with the molecular weight of the oligomer, which was more significant in the case of propylene oil. For ternary mixtures aPP-S-EHA copolymer/oligomer a maximum of adhesion can be observed if the content of the S-EHA copolymer in the mixture reaches about 30 mass-%. In the absence of oligomers in the mixture a minimum of adhesion can be observed for this composition, which can be attributed to the incompatibility of the remaining components.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 87
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 107-119 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: After comparison of three catalyst systems, i.e. [Nd(Oct)3/Al2Cl3ET3/Al(i-But)3, Ni(Oct)2/BF3OEt2/AlEt3 and Al(i-But)3/I2/TiCl4] the titanium catalyst system was used for the copolymerization of 1,3-butadiene with propylene oxide. The effects of monomer ratio on copolymer composition, conversion, microstructure, molar mass and molar mass distribution as well as of time of polymerization and of the aluminium/titanium ratio were evaluted. The copolymerization parameters were determined according to Kelen-Tüdős as rbutadiene = 0,9 and rpropylene oxide = 3,9. Copolymerization was confirmed by 13C NMR spectroscopy and extract evaluation combined with 1H NMR spectroscopy.
    Notizen: Für die Copolymerisation von 1,3-Butadien mit Propylenoxid wurde nach dem Vergleich der drei Katalysatorsysteme Nd(Oct)3/Al2Cl3ET3/Al(i-But)3, Ni(Oct)2/ BF3OEt2/AlEt3 und Al(i-But)3/I2/TiCl4 das Titankatalysatorsystem eingesetzt. Neben dem Einfluß der Monomerzusammensetzung auf den Umsatz, die Microstruktur, die Copolymerzusammensetzung, die Molmassen sowie die Molmassenverteilungen wurden auch die Polymerisationszeit und das Aluminium/Titan-Verhältnis untersucht. Die Copolymerisationsparameter wurden nach Kelen-Tüdős zu rButadien = 0,9 und rPropylenoxid = 3,9 bestimmt. Der Copolymernachweis erfolgte über 13C-NMR-Spektroskopie und Extraktionsuntersuchungen in Verbindung mit 1H-NMR-Spektroskopie.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 88
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 191-199 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Phosphorhaltige Polyurethane (PU-P) auf der Basis von Bisphenol A wurden durch N-Alkylierung hergestellt und mittels IR- und 1H NMR-Spektroskopie charakterisiert. Physikalische und thermische Eigenschaften dieser Polyurethane wurden mittels Differentialkalorimetrie, Thermogravimetrie, Röntgenbeugung und Untersuchungen der Löslichkeit, der Feuerbeständigkeit (Sauerstoffindex, LOI) und der reduzierten Viskosität bestimmt. Die Glastemperaturen der N-alkylierten Polymeren sanken von 120°C für das Ausgangspolymere bis auf 29°C für das N-alkylierte Polyurethan mit 2 Gew.-% Phosphor. Die Viskosität der N-alkylierten Polyurethane nahm von 0,36 dL g-1 auf 0,24 dL g-1 ab. Die phosphorhaltigen Polyurethane besitzen eine geringere thermische Stabilität und bessere Löslichkeit sowie höhere Feuerbeständlgkeit als das Ausgangspolymere. Die Röntgenstreuexperimente ergaben, daß ein erhöhter Phosphorgehalt der Polyurethane die Kristallinität herabsetzt.
    Notizen: Phosporus-containing polyurethanes (PU-P) based on bisphenol A were prepared by N-alkylation. The structures of N-alkylated polyurethanes were characterized by IR and 1H NMR spectra. Physical and thermal properties of the phosphorus-containing polyurethanes were investigated with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction, tests of solubility, limiting oxygen index (LOI) and reduced viscosity. Tg of the N-alkylated polymers decreased from 120°C for the starting polymer to 29°C of the 2.0 wt.-% phosphorus-containing polyurethanes. The viscosity of N-alkylated polyurethanes also decreased from 0.36 dL g-1 to 0.24 dL g-1. The thermal stability of polyurethanes decreased on the introduction of phosphorus groups. The LOI values of polyurethanes showed that fire resistance of phosphorus-containing polyurethanes was enhanced. X-ray diffraction measurements showed that the increased phosphorus content was accompanied by decreased crystallinity of the polyurethanes. The solubility of PU-P was improved.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 89
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: This question was addressed using various methods to monitor the process of curing and state of the final network. Attention was particularly focused on the possible inhomogeneous network formation as a consequence of the crosslinking process. An analysis of experimental data has revealed that some cured resins can be considered as homogeneous as the corresponding uncrosslinked materials. Resins cured by simple stepwise alternating chemistries, with good compatibility of components, usually fulfill the criterion of homogeneity. A family of epoxy resins cured with polyamines belongs to this category. Nodular structures seen by electron microscopy are a result of interaction of the electron beam or etching. Such structures are also observed for uncrosslinked polymers investigated under the same conditions. Formation of inhomogeneities in a number of thermoset systems is due to (a) chainwise mechanism of network formation with fast propagation inducing cyclization and steric volume exclusion and (b) poor compatibility of components of the system made stronger by increasing molecular weights and crosslinking during curing. Networks formed by freeradical polymerization and copolymerization of polyvinyl monomers can serve as an example of crosslinking-driven formation of inhomogeneities.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 90
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The base and transition metal catalyzed isomerization of allyl and crotyl ethers affords a facile, high yield route to the preparation of a variety of mono-, di-, and multifunctional 1-propenyl and 1-butenyl ethers. Employing this novel method, monomers containing epoxide, ester, ether carbonate and urethane groups can be prepared from their readily available allyl and crotyl precursors. In general, these monomers display very high reactivity in cationic polymerizations. In our work, we have focused on photoinduced cationic polymerizations of these monomers using diaryliodonium and triarylsulfonium salt photoinitiators. To study these very fast photopolymerizations, extensive use of real-time infrared spectroscopy was made. Employing this technique, the effects of monomer and photoinitiator structure on the rates of polymerization were studied.
    Zusätzliches Material: 1 Ill.
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  • 91
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 137-149 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Rubber elasticity is associated with changes in configurational entropy of a long chain. Because the chain cannot change its configuration instantaneously, there is a time delay in deformation to an applied force. This delayed response is the source of viscoelasticity and hysteresis energy loss of elastomer networks. Many tire performance properties are related to the viscoelasticity of tire components. Wet and dry traction of tire is related to the energy loss of the tread material at very high frequencies. On the other hand, rolling resistance of tire is characterized by the energy loss of tread material at relatively low frequencies. The dynamic viscoelastic properties of elastomer network shows characteristic zones on a frequency scale. At very high frequencies the energy loss is controlled by the segmental motions of the polymer chain. At lower frequencies the energy loss is related to the longer range motions of the chain. A series of polymers was synthesized to study the effect of micro- and macro-structure of the polymer on the viscoelastic properties of tread compounds and their tire performance properties. As expected from the theory, the wet traction of the tire was highly correlated to the segmental motions of the chains; namely, the glass transition temperature of the polymer. The energy loss of the compounds at a higher temperature, however, was related to the macrostructure of the polymer chain. Those examples illustrate that the fundamental understanding of the theory of elastomer network allows a tire engineer to obtain the best balance of tire performance characteristics.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 92
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 171-180 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Cationic, anionic, and radical ring-opening polymerization of spiro and bicyclic monomers, and their application to network polymers have been developed. Bicyclo orthoesters (BOEs), spiro orthoesters (SOEs), and spiro orthocarbonates (SOCs) were polymerized by cationic double ring-opening. Bicyclobis(γ-butyrolactone)s and spirobis(γ-butyrolactone)s were copolymerized with epoxides by anionic alternating ring-opening. Polymers from SOCs bearing exomethylene groups consisted of ring-opened and vinyl polymerized units. The degree of ring-opening of SOCs depended upon the number of rings and steric hindrance. The radical polymerization of vinylcyclopropanone cyclic acetals depended on the ring-size. With the monomers bearing 5- and 6-membered acetal rings, single ring-opened polymers were obtained. With the monomer bearing 7-membered acetal ring, the polymer mainly consisted of double ring-opened unit. These monomers could be crosslinked by bifunctionalization. Poly(cyclic orthoester)s linked by covalent bonds with dithiols to bifunctional SOEs were crosslinked by acid catalysts, and the reversible crosslinking-depolymerization system could be controlled by temperature.
    Zusätzliches Material: 1 Ill.
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  • 93
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 240 (1996), S. 205-211 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polyester urethane network elastomers with incorporated hard segment oligomers have been prepared by poly(ethylene adipate)glycol (PEA), 2,4-tolylene diisocyanate (TDI), and 1,4-butanediol (BD). These hard segment oligomers were hydroxy-terminated oligomers ([BD-TDI]n-BD; n=1,3), obtained by reacting BD with TDI. Concentrations of allophanate as a cross-linking site were determined by the amine degradation method. Hard segment moieties were obtained by a novel selective hydrolysis of soft segments in the elastomers. Molecular weight distributions of hard segment were measured by means of GPC. Mechanical and thermal properties were measured. Dependence of rubber elasticity on physical cross-linking between normal elastomers and the elastomers with incorporated hard segment oligomers were discussed.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 94
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Poly (vinyl alcohol) with pendent styrylpyridinium groups (SbQ) is insolubilized by photoirradiation. An association takes place in SbQ groups. The association of polymer chains becomes marked with increasing the number of SbQ groups. Mainly intermolecular crosslinks were formed. Transparent and homogeneous macrogels consisting of several intermolecular crosslinks are obtained.The proportion of the free water to the bound water in PVA-SbQ gels was 3.3-2.9 despite of the large change in conversion of photodimerization of SbQ groups, x=0.27-0.58. The water uptake after swelling of the gels in water increased 6-27 times compared to the original weight at pH=7. The higher the degree of photocrosslinking, the lower was the degree of swelling. The water diffusion coefficients, D, were (2.2-5.8) × 10-5 cm2 S-1 for a 88% saponified PVA with 1 . 3 mol% SbQ groups. The volume of the gel increased discontinuously about 10-fold for the 99% saponified PVA with 0 . 096 mol% SbQ and 51% water (49% acetone). The acetone concentration at the transition decreased with increasing the degree of saponification of the PVA.
    Zusätzliches Material: 10 Ill.
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  • 95
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 151-160 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Durch anionische Copolymerisation von Allylmethacrylat und Methylmethacrylat wurden Makromonomere unterschiedlicher Kettenlänge mit durchschnittlich drei Allyl-Doppelbindungen pro Kette hergestellt́ und mit NMR-Spektroskopie und Gelpermeationschromatographie charakterisiert. Durch Copolymerisation der Makromonomeren mit 1-Vinyl-2-pyrrolidon wurden dreidimensionale Strukturen erhalten. Die optischen und mechanischen Eigenschaften der Produkte wurden untersucht, und die Quellungseigenschaften und Vernetzungsgrade wurden bestimmt. Die Copolymereigenschaften wurden durch Makromonomere mit Kettenlängen bis 40 Einheiten nur wenig beeinflußt. Bei Kettenlängen über 50 Einheiten wurde eine leichte Abnahme der Wasseraufnahmefähigkeit und eine deutliche Erhähung des Elastizitätsmoduls beobachtet. Die Vernetzungsgrade hängen von der Makromonomer-Kettenlange ab; eine merkliche Erhöhung aufgrund der groößeren Zahl an Methyl-Methyl-Wechselwirkungen wurde bei Kettenlangen über 50 Einheiten festgestellt. Die Copolymeren zeigen günstige Festigkeits-Dehnungs-Eigenschaften und einen geringen Gehalt an wasserlöslichen Extrakten, in denen durch IR-Spektroskopie 1-Vinyl-2-pyrrolidon-Homopolymere identifiziert wurden. Obwohl mit allen untersuchten Makromonomeren gute Resultate erzielt wurden, scheint für die Copolymerisation mit 1-Vinyl-2-pyrrolidon das Makromonomere mit 50 Einheiten am besten geeignet.
    Notizen: Macromonomers of various chain lengths with an average of three allyl double bonds per chain were prepared by anionic copolymerization of allyl methacrylate with methyl methacrylate. The macromonomers were characterized by gel permeation chromatography and nuclear magnetic resonance. The macromonomers were then copolymerized with 1-vinyl-2-pyrrolidone to form three-dimensional structures. Their optical, swelling and mechanical properties were studied and the crosslinking efficiency was determined. The copolymer properties are not greatly affected by macromonomer chain lengths up to 40-mers; above 50-mers there is a slight decrease in the equilibrium water content and a significant increase in the modulus of elasticity. The crosslinking efficiency depends on the macromonomer chain length; a marked increase was observed for the 50-mer because of a greater number of methyl-methyl interactions. Copolymers have favourable strength-strain properties and a low content of water-soluble extracts, in which the IR analysis demonstrated the presence of 1-vinyl-2-pyrrolidone homopolymers. In spite of the good results obtained for all the macromonomers described in this work, the 50-mer seems to be optimal for copolymerization with 1-vinyl-2-pyrrolidone.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 96
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 239 (1996), S. 201-213 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: The curing of diglycidyl ether of bisphenol A (DGEBA) with 2,6-dimethylol-p-cresol modified by hexahydrophthalic acid anhydride was investigated and compared with the analogous in situ curing of DGEBA, hexahydrophthalic acid anhydride and 2,6-dimethylol-p-cresol. The chemical reactions were investigated by means of titration and different spectroscopic and chromatographic methods. It was examined whether the less complicated and therefore cheaper in situ reaction delivers postcured products with equal or better properties. Furthermore, it was investigated whether the results are similar using technical phenolic hardeners.
    Notizen: Die Härtung von Diandiglycidylether (DDGE) mit hexahydrophthalsäureanhydridmodifiziertem 2,6-Dimethylol-p-kresol (HHPSA-DMPK) wurde untersucht und mit der in situ durchgeführten Vernetzung von DDGE mit Hexahydrophthalsäureanhydrid (HHPSA) und 2,6-Dimethylol-p-kresol (DMPK) verglichen. Die chemischen Reaktionen wurden durch Titration der Epoxidgruppen und mit verschiedenen spektroskopischen und chromatographischen Methoden untersucht. Es wurde geprüft, ob die weniger aufwendige und daher preiswertere in situ-Härtung zu Produkten mit gleichen oder besseren Endeigenschaften führt. Weiterhin wurde die Übertragbarkeit der Ergebnisse auf den Einsatz technischer Phenolharzhärter getestet.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 97
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Zur Entwicklung neuartiger ökologisch verträglicher makromolekularer Schlichtemittel wurden in früheren Arbeiten Copolymerisationsreaktionen zwischen Polyvinylalkohol (PVA) und Stärke unter Verwendung von chemisch reaktiven bifunktionellen Verbindungen wie N-Methylolacrylamid beschrieben. Im Rahmen dieser Arbeit werden die physikochemischen Eigenschaften des resultierenden Copolymeren untersucht. Von Bedeutung sind hierbei insbesondere Merkmale wie Molekulargewichtsverteilung, Klebekraft, Stabilität, Löslichkeit sowie rheologische Eigenschaften. Derartige Kenntnisse über die physikochemische Beschaffenheit der PVA-Ausgangsverbindung sowie des makromolekularen Endproduktes sind eine wesentliche Voraussetzung für die Entwicklung von neuen Produkten, die als wasserlösliche, recycelbare Schlichtemittel zur Anwendung in der Textilindustrie kommen können.
    Notizen: A macromolecular sizing agent based on the copolymerization of poly(vinyl alcohol) (PVA) with hydrolysed starch was prepared using the chemically reactive bifunctional compound N-methylolacrylamide. Detailed characteristics of the resultant PVA/N-methylolcarbamoylethylated starch copolymer were studied where emphasis has been placed on solubility, rheological properties, molecular weight distribution, adhesive power and stability. Elucidation of the nature of the macromolecular segments of both N-methylolcarbamoylethylated PVA as well as PVA/N-methylolcarbamoylethylated starch copolymer fulfilled the prerequisite to tailor PVA/starch copolymer which is appropriate for application as a water-soluble recyclable sizing agent by ultrafiltration.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Seismic isolation was reconfirmed to be extremely efficient for the protection of buildings, and hence human life, on the occasion of the Great Hanshin Earthquake. Rubber bearings are placed under the buildings for isolation, and thus the type of rubber bearings is a dominant factor for efficient isolation. In this report, the performance of peripherally restraining type rubber bearing (PRB) was examined where its contracted model was found to simulate the performance of full scale PRB precisely. Damping ratio and vertical spring constant of PRB are as good as the existing ones. PRB showed lower critical shear strain, but it was concluded that no problems were found for the actual use of PRB.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The network formation of phenol-formaldehyde resin was investigated by the Monte Carlo (MC) simulation technique. The observed value of the gel point, pc, was exactly determined as a critical extent of reaction, where the Mw/Mn in soluble parts is maximum. The MC simulation with the cubic percolation theory was applied to the gelation of phenolic resins and gave an exact gel point, which was in excellent agreement with the observed value of pc. The simulation showed that the intramolecular reaction occurred frequently with increasing the gel fraction beyond the gel point. The structural analysis of the maximum cluster with the computer strongly supported the contribution of the intramolecular reaction to the network formation of the gel.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The structure of the hydrogel of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA) was investigated by small angle X-ray scattering (SAXS) of synchrotron radiation. A physically crosslinked blend gel, which was prepared by repetitive freezing and thawing of an aqueous solution of PVA and PAA, could be chemically crosslinked by esterfication of PVA with PAA even in the hydrogel state. The chemical crosslinking induced the destruction of physical crosslinks into a folded structure, indicating that the chemical crosslinking proceeds at the sites around the physical crosslinks that contain PVA and PAA in much higher concentration than other portion of the gel. The pH-induced structure changes of the PVA hydrogels, chemically crosslinked with poly(acrylic acid) (PAA) were investigated by SAXS on the samples of various chemical crosslinking time. The gels were shrunk at pH4, and swollen at pH8. The results of SAXS showed, that the Porod slope changed with chemical crosslinking time from -3.5 to -2.9 at pH4, and from -2.9 to -2.4 at pH8. The results suggest that a folded structure as a structural domain, which is characterized by fractally rough interface, tends to change into the structure that corresponds to percolation cluster, particularly at pH8. The gels immersed in pH8 showed a remarkable structure change accompanying swelling. The results revealed that a conformational change of PAA chains, induced by the pH change, can be explained by the presence of a structural domain in the gel network, where both PVA chains and PAA chains get entangled and partially form a interpenetrating polymer network(IPN).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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