THEORY OF THERMOELASTIC PROPERTIES FOR POLYMER GLASSES

We derive expressions for the extensional elastic moduli as functions of temperature and pressure by a generalization of the equation of state theory. Our previous efforts in this direction were confined to the low-temperature region, where the characteristic free volume function, defined by theory, is effectively frozen. We proceed now to higher temperatures, where the temperature and pressure dependence of this function play a decisive role. The static Young's and shear modulus and the Poisson ratio are computed, based solely on equation of state information. This is illustrated by means of applications to poly(vinyl acetate) glasses at low and elevated pressures and for different formation histories.