Polymer Elasticity Nature in the Transition Zone

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Abstract
In the zone of transition from the glass-like to rubber-like state the change of polymer elasticity mechanism takes place from entropy to energy nature. On the basis of phenomenological photoelasticity theory in non-equilibrium state the separation method for the energy and entropy components of stress is suggested. It is pointed out that the correction for kinetic factor T/T 0 (T and T 0 are experimental and reduction temperatures, correspondingly) has to be introduced not for the entire stress but for its entropy component only while using the time-temperature reduction principle. The results of combined measurements on stress and birefringence relaxation in butadiene-acrylonitrile vulcanizate are presented within the temperature limits from – 26.4 to 25°C and time limits from 0.4 to 1000 sec. From the data obtained the reduced master curves of entropy modulus component and entropy relaxation spectrum have been calculated. The latter has the form in accordance with the predictions of the molecular theory of polymer viscoelasticity.