Volume and enthalpy relaxation in a-PMMA after temperature up-jumps

Abstract

The volume and enthalpy relaxation in a-PMMA subjected to temperature jumps in T-g region has been analysed. The measured Hand Vdata were compared with respect to aging time and proportionality between them as a slope of (partial derivativeH/partial derivativeV)(T) dependencies has been found. According to previous works the slope was identified as an apparent bulk modulus, K-a. This method is applied to aging following temperature up-jumps after consolidation periods of varying lengths. The main finding is a marked increase of K-a with consolidation time, approaching a limiting value in an asymptotic fashion.