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  • Polymer and Materials Science  (5)
Material
Years
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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 2919-2933 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A sample of polystyrene with narrow molecular weight distribution (M̄w/M̄n = 1.03) has been formed into a 3-mm sheet and subjected to γ-irradiation at 25°C in air. Simultaneous crosslinking and scission of polymer chains resulted. Analyses by velocity and equilibrium sedimentation, gelpermeation chromatography, and osmometry of the polystyrene subjected to doses in the range 0-90 Mrad, all within the pre-gel region, have yielded average values of G(S) = G(X) = 0.022 ± 0.002 for the complete sample. Combination of these various experimental techniques has been successful in yielding consistent values of G(S) and G(X) and should be applicable with advantage to other polymers, particularly when neither G(S) nor G(X) is zero. The wide variation in literature values of G(S) and G(X) for irradiation of polystyrene under vacuum precludes any unequivocal conclusion on the effect of air on the radiation yields.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 131-139 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of γ-irradiation on poly(tert-butyl crotonate) has been investigated by velocity sedimentation and solubility studies. Evidence of significant crosslinking as well as of chain scission has been obtained, the estimates of G(X) and G(S) being 0.66 and 0.59, respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 4081-4088 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of molecular weight averages and distributions have been made on three samples of narrow molecular size distribution polystyrene with molecular weights from 100, 000 to 400, 000 subjected to 60Co γ irradiation in vacuo for various doses within the pregel region+ G(X), the radiation chemical yield of crosslinking, has been determined as 0.043 ± 0.002 and G(S)/G(X), the ratio of scission to crosslinking, as 0.02; no effect of molecular weight was observed. By comparison with previous experimental results for polystyrene irradiated in air it has been established unequivocally that an oxygen environment leads to enhanced scission at the expense of crosslinking. Literature values of G(X) and G(S)/G(X) are reviewed in the light of these results and explanations are offered to account for major discrepancies.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 24 (1979), S. 425-439 
    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: Irradiation of 3 mm polystyrene sheet in air at 30°C with γ rays caused a rapid decrease in the tensile and flexural strengths and strains to fracture. These properties were decreased to 50% of their initial values after ca. 80 Mrads and to 25% after ca. 200 Mrads, beyond which dose the rate of change was relatively small. These results contrast with the negligible changes that are observed after 600 Mrads in vacuum. The effect of irradiation in air has been correlated with decreasing molecular weight at the surface, even though crosslinking predominated over the complete sample so that a gel point was reached at a dose slightly in excess of 100 Mrads. Scission and crosslinking yields, G(S) and G(X), were determined as a function of depth by gel permeation chromatography of layers removed progressively from the surface. G(S) decreased and G(X) increased with depth, in accord with the concepts of increased scission by reaction with oxygen and a diffusion effect. Unusual transverse cracking to a limited depth occurred during tensile measurements, a phenomenon that is attributed to the nonuniform molecular weight profile.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1515-1518 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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