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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 5699-5705 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8870
    Keywords: polyphosphazene ; polystyrene ; blends ; XPS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Blends of polystyrene (PS) with poly(4-phenoxyphenoxy)phosphazene (PPA) were studied by differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). A third component, poly(2,6-dimethyl-1,4-phenylene ether) (PPE), was added to improve the compatibility. While DSC and XPS reveal that PS and PPA are incompatible, the presence of PPE increases the compatibility between the two polymers.
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  • 3
    ISSN: 1572-8870
    Keywords: polyphosphazene ; polystyrene ; blends ; X-ray photoelectron spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Blends of polystyrene (PS) with poly(phenoxy)phosphazene (PPN) were studied by differential scanning calorimetry (DSC) and X-ray photoelectron spectroscopy (XPS). A third component, poly(2,6-dimethyl-1,4-phenylene ether) (PPE), was added with the aim of increasing compatibility of the blends. T g values did not vary in the PS/PPN blends, indicating that the components are substantially incompatible. The addition of PPE did not change the situation much even though some compatibility between PPN and PPE was detected. XPS on the cast films showed that only PPN was present at the surface. The surface composition of the blends was found to be dependent on the preparation technique.
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  • 4
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Samples of poly(ethylene terephthalate) (PET), poly(ethylene terephthalate-co-naphthalene-2,6-dicarboxylate) (PENT) and poly(ethylene naphthalene-2,6-dicarboxylate) (PEN), materials which find application in textile and packaging industry, have been investigated, with the aim to obtain narrow molecular weight fractions suitable for further characterization. Preliminary results concerning with the fractionation of gram-quantities of the polyesters are reported, using a method based on the fractional precipitation from a phenol/1,2,4-thrichlorobenzene solution of the polymer, using n-heptane as non-solvent. Obtained fractions have been characterized by intrinsic viscosity measurements and Gel Permeation Chromatography analysis.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 225 (1995), S. 109-122 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(ethylenterephthalat)-(PET)-Rezyklat aus gebrauchten Getränkeflaschen wurde bei 150-220°C im Vakuum behandelt oder bei mehreren Temperaturen mit zwei unterschiedlichen Durchsatzgeschwindigkeiten extrudiert. Nach anschließender Extraktion wurden die erhaltenen niedermolekularen Verbindungen mittels Hochleistungs-Flüs-sigchromatographie (HPLC), Größenausschlußchromatographie (SEC) und Massenspektrometrie mit chemischer Ionisierung (DCI/MS) untersucht. Die Verteilung von cyclischen und linearen Oligomeren mit Polymerisationsgraden von 2 bis 6 im Extrakt wurde bestimmt. Als Folge der Vakuumbehandlung des PET nimmt der Oligomergehalt mit steigenden Temperaturen ab. Umgekehrt führt die Extrusion bei ansteigenden Temperaturen (ebenso bei längeren Aufbewahrungszeiten) zu höheren Oligomerkon-zentrationen. Außerdem wurden bei zunehmenden Aufbewahrungstemperaturen und -zeiten breitere Molekulargewichtsverteilungen beobachtet, d. h. es wurden in zunehmendem Maße größere Ringe und längere Ketten gebildet. Eine bedeutende Menge an Oligomeren mit mittlerem Molekulargewicht wurde ebenfalls nachgewiesen.
    Notes: Low-molecular-weight compounds extracted from recycled poly(ethylene terephthalate) (PET) from post-consumer soft-drink bottles, treated at 150-220°C in vacuo or extruded at several temperatures and two different mass flow rates, were characterized by high performance liquid chromatography (HPLC), size exclusion chromatography (SEC) and desorption chemical ionization/mass spectrometry (DCI/MS). Among these products, cyclic and linear oligomers (polymerization degree 2-6) were identified, and their distribution was determined.As a consequence of vacuum treatment of PET, the overall oligomer content decreases with increasing temperatures. Conversely, the extrusion at crescent temperatures causes an increase of the oligomer concentration; the same effect was observed by increasing the residence time. A further effect was represented by the enlargement of molecular weight distributions, i.e. larger rings and longer chains were formed in greater amounts at higher temperatures and residence times; a significant fraction of medium-molecular-weight oligomers (M̄n = 1400-1900) was also formed.
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  • 6
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 1859-1866 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The microstructure of aromatic copolyesters prepared by bulk polymerization was investigated by means of 1H NMR spectroscopy. The aromatic region of the spectra appears to be sensitive to the sequence distribution of aromatic rings. Line shape simulation and resolution enhancement of the time domain spectra with a Gaussian window function allow a quantitative evaluation of the relative intensities. Sequence distribution in terms of triads and diads formed by aromatic rings was then derived and compared with the one calculated on the basis of a random distribution. The results show that the distribution, as expected for this class of copolymers, is random.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 3241-3248 
    ISSN: 0887-624X
    Keywords: poly(ester-amide)s ; bis(2-oxazoline)s polymerization ; bulk polymerization ; glass transition temperature ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of linear poly(ester-amide)s from monoanhydrides, bis(2-oxazoline)s (namely 2,2′-(1,4-phenylene)bis(2-oxazoline)) and a third comonomer is discussed. The polymerization reactions were carried out in bulk between 150 and 200°C. When the third monomer is a diol, poly(ester-ester-amide)s are obtained. Diols of different structure were used: α,ω-diols having up to 12 carbon atoms, ethylene glycol oligomers (two or three repeating units), cyclic diols, etc.; glutaric, 3,3-dimethylglutaric and maleic anhydrides were used as monoanhydrides. The polymers were studied from the point of view of thermal properties, finding a substantial agreement between the structure of the monomers and the glass transition temperature of the polymers. By using primary diamines as a third comonomer, the reaction does not lead to the formation of a polymeric product. The failure of the polymerization was attributed to a competitive reaction that prevents the polymerization. After the amine group has reacted with the anhydride, cyclization of the so-formed carboxyalkylamide occurs, giving an imide derivative, unable to react further. Therefore, only a mixture of low molecular weight compounds is obtained in this case. When the diamine is secondary, the imidization reaction is not possible, and linear poly(amide-ester-amide)s are obtained. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3241-3248, 1997
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2119-2126 
    ISSN: 0887-624X
    Keywords: stereospecific polymerization ; isotactic polystyrene ; nickel catalysts ; methylaluminoxane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polymerization of styrene using catalytic systems based on nickel derivatives and methylaluminoxane (MAO) was studied. Among tested catalysts, nickel bis(acetylacetonate) and nickel dichloride show the maximum activity. Bis(phosphine)nickel dichlorides exhibit lower activity, depending on the nature of the phosphine ligand. Polymer yields decrease by lowering the catalyst concentration, by increasing the reaction temperature, or by carrying out the polymerization in a polar donor solvent. Weight average molecular weight of most of the prepared polystyrenes ranges from 9000 to 25,000, with polydispersity indexes of 1.6-3.8. However, polystyrene prepared in dioxane solvent exhibits a small fraction of very high molecular weight (about 140,000). From NMR analysis, the products seem generally to be constituted of two polymers with different steric microstructure: atactic polystyrene and partially isotactic polystyrene (ca. 75-85% meso diads). Catalytic site specificity is correlated with the type of nickel ligand, while the effect of reaction temperature is less defined. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2119-2126, 1998
    Additional Material: 1 Ill.
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  • 9
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Processing of virgin and recycled poly(ethylene terephthalate) (PET) in a twin screw extruder evidences the degradative effect caused by thermal decomposition of poly(vinyl chloride) (PVC) and other impurities, e.g. adhesives, at the processing temperature. Lower melt viscosity and molecular weight, along with higher carboxylic end group concentration, were observed for recycled PET, the extent depending on PET purity. In an attempt to investigate the correlation between the kinetics of degradation phenomena and the level of thermomechanical stress, a novel dynamic method of evaluating thermal stability in processing conditions was developed. Such a method allows the achievement of long equivalent residence times while using lab-scale extruders. As a result of these experiments, PVC-rich recycled PET was shown to reach very low melt viscosity after less than 10 min in processing conditions, while virgin PET retained high viscosity even after 30 min.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1557-1566 
    ISSN: 0887-6266
    Keywords: polyesters ; PET ; PEN ; PEI ; 13C NMR ; dynamics ; nuclear relaxation times ; gas diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamics of amorphous aromatic polyesters consisting of poly(ethylene terephthalate) (PET), poly(ethylene isophthalate) (PEI), and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) has been investigated by means of solid state CPMAS 13C NMR. Proton T2, 13C T1ρ, and proton T1ρ decays have been measured in particular, and the experimental data fitted to suitable model functions to determine best relaxation parameters. The fitting results show for proton T2 and 13C T1ρ measurements the presence of two components with different relaxation times and intensities, arising from different motional domains. The proton T1ρ, on the contrary, shows a single component which limits the dimensions of the two regions to less than 20 Angstroms. The dependence of 13C T1ρ values on two different irradiating field strengths (H1 = 38 KHz, H1 = 60 KHz) allowed the assignment of each component to relatively rigid and mobile regions. By comparing the three polymers we observe that PEN and PEI have a similar relaxation behavior, while a higher fraction of mobile components was found for PET. These differences are believed to arise mainly from local motions of the aromatic rings. The relaxation measurements have been evaluated to suggest a correspondence to O2 and CO2 gas permeabilities in PET, PEI, and PEN. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1557-1566, 1998
    Additional Material: 7 Ill.
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