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  • Articles  (2)
  • Physics  (2)
  • 1970-1974  (1)
  • 1965-1969  (1)
  • 1
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Nylon 66 films exhibiting form I melting behavior show the γ mechanical relaxation at -140°C. Samples which have form II melting behavior do not show this relaxation. The γ relaxation disappears when material having form I behavior is converted to material having form II behavior by annealing or by cold drawing. The form I and form II types of melting behavior are also found in poly(ethylene terephthalate); the interconversions and thermal behavior of the forms are analogous to the nylon 66 case. In poly(ethylene terephthalate), the β relaxation at -40 to -60°C is present only when form I melting behavior is found. Conversion to form II melting behavior by annealing or drawing (80°C) again causes the relaxation to disappear. No β relaxation was found in amorphous polymer. The γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) can therefore be associated with the crystalline structure responsible for form I melting behavior. Form I melting behavior has been associated with foldedchain crystals based on previous work. It is therefore postulated that the γ dispersion in nylon 66 and the β dispersion in poly(ethylene terephthalate) are associated with motions in the chain folds. This assignment is not inconsistent with the change in the γ dispersion of nylon 66 with the number of backbone CH2 units, since these will affect the fold structure.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A technique for estimating Mc, the molecular weight between crosslinks, of amine-cured epoxy resins is described. The technique is based upon the stoichiometry of the curing reaction and the amount of primary amino and epoxy groups remaining in the polymer at a given time. The Mc values so calculated are shown to be consistent with Mc results obtained from separate measurements of swelling and the polymer-solvent interaction parameter χ1 for the range of polymer concentration in which both measurements could be obtained. A means of estimating the relative reaction rates of the primary and secondary amino groups with the epoxy groups is given. Under proper curing conditions the amine-epoxy reaction goes very nearly to completion. The presence or absence of an exotherm has no noticeable effect on the course of the reaction between bisphenol A-epichlorohydrin (Epon 828) and methylene dianiline.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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