SORPTIVE DILATION AND RELAXATIONAL PROCESSES IN GLASSY POLYMER GAS SYSTEMS - I - POLY(SULFONE) AND POLY(ETHER SULFONE)

The volumetric behaviour of glassy poly(sulfone) and poly(ether sulfon e) under gas pressures of CO2, N2O and CH4 up to 50 bar was investigat ed at 35 degrees C using a new experimental technique based on a capac itive distance measurement. Corresponding gas concentrations within th e polymers were determined by gravimetric gas sorption measurements. T he time-dependent dilation after a pressurising step reveals two disti nct dilation modes. The analysis of the first dilation mode according to mass transport kinetics is in good agreement with diffusion coeffic ients from time-lag experiments, whereas the slower secondary process has to be considered as volume relaxation resulting from the enhanced polymer chain mobility and the stress exerted by the sorbed gas molecu les. (C) 1998 Elsevier Science Ltd. All rights reserved.