THE RELATIONSHIPS BETWEEN POLYMERS AND GLASS TRANSITION TEMPERATURES
Technical rept. for Jun 1965-May 1966
AMERICAN CYANAMID CO STAMFORD CT CENTRAL RESEARCH DIV
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The glass transition is an experimental manifestation of the extremely large activation energies for molecular motion encountered as the temperature of a liquid is lowered. As an approach to the effect of molecular structure on this phenomenon, low-shear melt viscosities were obtained as a function of temperature for three homologous series of polymers polypropylene, polychlorotrifluorethylene and polypropylene oxide. A kinetic model of the glass transition was devised for computer simulation of dilatometric behavior in the region of a transition. The assumption that the dielectric and volume relaxation times are equal was shown to be satisfactory for prediction of dilatometric results on polymers. The effects of rate of heating, activation energy and coefficients of expansion on the measurement of transitions were demonstrated. The Gibbs-DiMarzio theory of the glass transition was cast in a form suitable for very short chains and shown to agree quantitatively with To values for the lower n-alkanes. The Eyring transition state theory of relaxation processes was shown to be applicable to dielectric relaxation in polymers with modification to allow for a temperature-dependent activation free energy.
- Polymer Chemistry
- Atomic and Molecular Physics and Spectroscopy