PERMEABILITY OF CARBON-DIOXIDE AT ELEVATED PRESSURES IN SUBSTITUTED POLYCARBONATES

Past work has shown that hysteresis in sorption, volume dilation, and permeation result when standard bisphenol A polycarbonate is conditioned by exposure to 900 psia carbon dioxide at 35°C. This article reports hysteretic permeation results for the same polycarbonate exposed to other carbon dioxide conditioning pressures. Furthermore, permeation results are reported for tetramethyl and hexafluoropolycarbonate following conditioning with carbon dioxide. Permeation measurements with these structurally related polycarbonates show qualitatively similar, but quantitatively smaller long‐lived hysteretic effects compared with standard polycarbonate dilated to similar volume percentages. The percentage increase in permeability following conditioning treatments will be discussed in terms of fractional free volume considerations. Copyright © 1990 John Wiley & Sons, Inc.