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  • Polymer and Materials Science  (2)
  • Electron microscopy
  • 1960-1964  (2)
Collection
Keywords
  • Polymer and Materials Science  (2)
  • Electron microscopy
  • Chemistry  (2)
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 42 (1960), S. 35-48 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular weight distributions have been found for fractions of polystyrene degraded ultrasonically in benzene solution at very low concentrations (0.002% w/v). The distributions show that little, if any, of the degradation products include molecules of molecular weight less than 50,000. The variation of the rate constant for the degradation of the molecules with molecular weight follows the theoretical relation being proportional to M2.82 derived in Part I up to molecular weights of 106. Beyond this value the rate constant increases at a slower rate. This is attributed to a change in the variation of the shock pressure and rear flank of the shock wave with distance from the cavity. The rate constant for a given fraction reaches a peak at a concentration of about 0.01% w/v after which it falls rapidly with increasing concentration. This is attributed to the formation of a network by the polymer which reduces the rate of the cavity collapse.
    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 Part A: General Papers 2 (1964), S. 2875-2882 
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Some graft copolymerizations of monomers with substrates previously irradiated in air to form polymeric peroxides have been studied at pressures up to 8000 atm. In the heterogeneous system styrene-irradiated polyethylene, the rate of grafting increases considerably with pressure up to about 3000 atm. At higher pressures the reaction is retarded, and this is attributed to diffusion control of the propagation reaction. The rate of homopolymerization increases exponentially with pressure over the range 1-4000 atm. Irreproducible results were obtained when methyl methacrylate was used in place of styrene, possibly because the substrate is not swollen by this monomer. No grafting was observed between five different chloro-substituted ethylenes and irradiated polyethylene at pressures up to 5000 atm. The rate of grafting in the homogeneous system vinyl acetate-irradiated polystyrene increases considerably with pressure up to 8000 atm., and there is no indication of diffusion control of the propagation reaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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