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  • Articles  (3,749)
  • Chemistry  (2,816)
  • Humans  (940)
  • Analytical Chemistry and Spectroscopy  (328)
  • 1985-1989  (1,828)
  • 1980-1984  (1,230)
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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 509-519 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: The deterioration of polyolefin, poly(ethylene terephthalate), and polyamide films under soil burial conditions extending up to 32 months has been investigated. Based on changes in their elongation at break, the films can be ranked in order of increasing sensitivity to degradation: Polyester ≃ polypropylene 〈 low-density polyethylene ≃ high-density polyethylene 〈 nylon 6.6. The degraded nylon 6.6 and polyethylene films were characterized by infrared and luminescence spectroscopy and scanning electron microscopy, as well as by wet analysis for hydroperoxides. From a comparison with the well-known oxidative sensitivity of nylon 6.6 in oxygenated water at slightly elevated temperatures, the rapid deterioration of nylon 6.6 film during soil burial was also concluded to be an oxidative process. The somewhat smaller, but significant, embrittlement of the polyethylenes studied could not be simply explained by thermal oxidation (with only trace oxidation products detectable) or microbiological attack (deterioration being unaffected by surface activation to enhance wettability).
    Additional Material: 5 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 22 (1978), S. 2217-2228 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: The destruction of various UV stabilizers in polypropylene films during irradiation has been examined both in the presence and absence of air and oxidation products. Although some stabilizers were destroyed in the absence of oxygen, all were more sensitive when irradiated in the presence of air. Several stabilizers were highly effective but were destroyed so rapidly that photoprotection of the polymer must have resulted from stabilizer products. Work with preoxidized polymer and with model hydroperoxides and peroxides indicated that most stabilizers were destroyed by the attack of oxygen-centered radicals, with peroxy radical attack appearing to dominate.
    Additional Material: 8 Ill.
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  • 13
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: A D2-m-dodecacarboranesiloxane containing alternating block copolymer \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}[{\rm A}\hbox{---}{\rm B}\rlap{--}]_n$\end{document} was prepared by the reaction of a ureidosilane-terminated polysulfone hard block with a carboranesilanol-terminated carboranesiloxane oligomer. The resulting block copolymer exhibited thermoplastic elastomeric behavior. This unique polymer had excellent thermal stability up to 400°C.
    Additional Material: 5 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 4959-4969 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Structure property relationship of four different diisocyanates is studied in detail. The isocyanates selected are TDI, MDI Crude, HDI, and IPDI. Physical properties such as mechanical, dynamic mechanical, electrical, and thermal are studied. Dynamic mechanical analyses are based on the compound resonance principle. Among all, IPDI-based polymer showed mediocre trend and TDI-based polymer showed best properties.
    Additional Material: 4 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 131 (1985), S. 145-155 
    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: The application of electron irradiated polypropylene granulate as a nucleating agent in extrusion has recently been suggested. This article discusses the chemical characterisation of such an electron treated granulate. Since the irradiation is carried out under atmospheric conditions, the relationship between decomposition, crosslinking and oxidation products has been determined. Oxidation is confined principally to the outermost molecular layers and leads to the formation of carbonyl groups via peroxide intermediates. As well as specific group tests, ESCA has been used to measure the degree of oxidation and for indirect determination of vinyl groups after bromination.
    Notes: In jüngster Zeit wird der Einsatz von elektronen-bestrahltem Polypropylengranulat als Nukleierungsmittel bei der Extrusion vorgeschlagen. Die vorliegende Arbeit beschäftigt sich mit der chemischen Charakterisierung der elektronen-bestrahlten Granulate. Da die Bestrahlung unter atmosphärischen Bedingungen stattfindet, werden nicht nur der Zusammenhang von Abbau und Vernetzung, sondern auch Oxidationsprodukte bestimmt. Die oxidative Schädigung findet hauptsächlich in den oberen Moleküllagen statt und führt über peroxidische Zwischenprodukte zur Entstehung von Carbonylgruppen. Neben für funktionelle Gruppen spezifischen Nachweismethoden wird die oberflächen-spezifische ESCA-Methode zur Erfassung des Oxidationsgrades und zur indirekten Vinylgruppenbestimmung nach der Bromierung eingesetzt.
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  • 16
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The provision of accurate composition-depth profiles to depths 〉 1 μm is important in the characterization and investigation of thick films, surface coatings, surface treatments and many other technologically important applications. At present, such profiles are usually achieved by sequential ion bombardment and surface analysis and hence involve many difficulties in interpretation due to the non-uniform erosion of surfaces under ion bombardment. In this paper a method of obtaining accurate depth profiles is described using a ball-cratering device. The method employs a rotating ball to fashion a well-defined spherical crater in the sample surface, the depth and width of which can be accurately controlled. The specimen is then cleaned in situ using a scanning ion beam for a short period and the composition-depth profile is obtained either by point-by-point analysis down the sloping sides of the crater wall or by using Auger line-scan techniques across the crater. Coating-substrate interface analysis can also be obtained by sputter-depth profiling at a point on the coating close to the exposed substrate. The method is not only considerably faster than ion etching, but the resulting depth profile also has a well-defined depth resolution. Composition-depth profiles through nitrocarburized mild steel surfaces and protective surface coatings are presented to illustrate the usefulness of the technique.
    Additional Material: 10 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 2 (1980), S. 5-10 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mean free paths for inelastic scattering (λ) of low energy electrons in poly(methylmethacrylate) (PMMA) have been determined by measuring Al Kα excited C 1s and Si 2s photoelectron signal intensities as a function of ellipsometrically determined thicknesses of PMMA overlayers on silicon substrates. The λ values obtained are 29 ± 4 Å for 1196 eV electrons and 33 ± 5 Å for 1328 eV electrons. These data are necessary for the quantitative analysis of the surface region of PMMA and similar polymers by X-ray photoelectron spectroscopy (XPS). The magnitude of the λ values determined indicates that XPS measurements can provide chemical information about the surface region of polymers, such as PMMA, in the depth range of ∼6 to 100 Å. The results of this study are compared and discussed with respect to λ values determined for other organic compounds.
    Additional Material: 7 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 10 (1987), S. 338-342 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Multi-element (52Cr, 56Fe and 66Zn) implanted GaAs samples have been prepared specially for SIMS calibration. Absolute chemical measurements gave retained ion doses which agreed to within 12% of the nominal implanted dose (2.0 × 1014 atoms cm-2). Comparative SIMS depth profiles with five instruments gave Cr mode depth data which showed a variability of 5%. After data normalization to a common mode depth (168 nm) the shape of all profiles showed good agreement. SIMS anàlysis of similar samples containing lower dose implants (1.0 × 1013 atoms cm-2) showed that ∼50% of the Cr was contained in the near surface region (0-0.03 μm). This surface peak was not observed in profiles of samples which had been singly implanted with Cr. It is proposed that the Cr surface peak results from radiation enhanced out-diffusion initiated by the subsequent Fe implant. Whilst the high dose multi-implant samples showed a similar Cr surface accumulation, its magnitude in relation to the ion implanted dose, was smaller. These samples therefore form reliable calibration specimens for the simultaneous determination of the secondary ion responses of Cr, Fe and Zn in GaAs.
    Additional Material: 4 Ill.
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  • 19
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The supermolecular structures of polyethylene filaments prepared by crystallization from solution in extensional flow at different crystallization temperatures as well as of annealed and zone-drawn samples have been characterized by means of X-ray diffraction methods. The lattice distortions in the crystallites of such samples are quantitatively determined for the first time. The results show that a direct correlation between the crystallite dimensions and the amount of lattice distortions on the one hand and the axial Young's modulus on the other hand can be excluded. Based on X-ray, mechanical and shrinkage investigations, some parameters of the structure of the non-crystalline regions are estimated. A structure model for the high-modulus polyethylene filaments is discussed.
    Notes: Die übermolekulare Struktur scherkristallisierter PE-Fäden unterschiedlicher Kristallisationstemperatur sowie getemperter und zonengereckter Proben wird mittels Röntgenbeugung charakterisiert. Erstmalig an derartigen Fäden werden die Gitterstörungen in den Kristalliten quantitativ angegeben. Die Ergebnisse zeigen, daß ein direkter Zusammenhang zwischen den Kristallitgrößen und dem Ausmaß der Gitterstörungen einerseits und dem axialen E-Modulandereseits ausgeschlossen werden kann. Auf Basis von Röntgen-, Modul- und Schrumpfmessungen werden Abschätzungen zum Aufbau der ungeordneten Bereiche durchgeführt und daraus Modellvorstellungen zur Struktur hochmoduliger PE-Fäden mitgeteilt.
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  • 20
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Mittels der Feldgradienten-Impuls-NMR wurden die Selbstdiffusionskoeffizienten Ds der Makromolekiile in an Luft γ-hestrahlten Polyethylenproben in Abhangigkeit von Ds von der Schichttiefe gemessen. Auf Basis der chemischen Reaktionen der Radikale wird eine Gleichung abgeleitet, die die Abhangigkeit von 8,von der Schichttiefe in Gebieten mit kinetisch und diffusiv kontrollierter Oxidation beschreibt. Der Einflulß der Kristallinitat sowic der Intensitat und Temperatur der Bestrahlung auf die Dicke der oxidiertcn Schicht wird untcrsucht.
    Notes: Layer-by-layer study of commercial polyethylene samples, γ-irradiated in air, was carried out by measuring the selfdiffusion coefficient Ds of macromolecules by means of pulsed field gradient NMR. On the basis of chemical reactions of the radicals an equation is obtained, describing the dependence of Ds on the layer depth in the kinetic and diffusive oxidation regions. The effect of crystallinity, radiation intensity and temperature on the thickness of the oxidized layer is examined.
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