KINETICS OF CO2 CONDITIONING OF COPOLYMERS AND BLENDS CONTAINING MMA UNITS

Long‐term, high‐pressure CO2 permeation experiments were conducted for styrene/methyl methacrylate (SMMA) random copolymers and bischloral polycarbonate/poly (methyl methacrylate) miscible blends to investigate the effects of gas conditioning. The extent and rate of CO2 permeability changes with time increased dramatically with content of MMA units in both series when compared at a constant upstream CO2 pressure of 20 atm. The higher solubility of CO2 in PMMA than polystyrene or the polycarbonate was found to be responsible for a part but not all of this response as shown by isobaric versus isoconcentration experiments. The rate of conditioning cannot be described by a single relaxation time. The conditioning process discussed here seems to be intimately connected to the plasticization process reported earlier for these same systems. Copyright © 1990 John Wiley & Sons, Inc.