Volume relaxation and physical aging of amorphous polymers I. Theory of volume relaxation after single temperature jumps

Abstract

The theory of volume relaxation, based on free volume, is briefly reviewed. Emphasis is placed on demonstrating the necessity of the introduction of a retardation time spectrum for the description of the volume relaxation behavior.

For simple approach experiments after a single temperature jump from equilibrium, a comparison between experiment and theory is made, using a one-parameter model as well as a multiparameter model. In the case of isothermal contraction, a good description is obtained for both models in a temperature range down to 50 K belowT _g. Extending the investigations to isothermal expansion experiments, it becomes necessary to use the multiparameter model.