SORPTION AND PARTIAL MOLAR VOLUMES OF ORGANIC GASES IN RUBBERY POLYMERS

Sorption of organic gases (C2H4, C2H6, C3H6, C3H8, n-C4H10, iso-C4H10, and n-C5H12) in two rubbery polymers, 1,2-polybutadiene and poly(ethylene-co-vinyl acetate), and dilation of the polymers due to sorption are measured as a function of gas pressure at 25-degrees-C. Sorption isotherms for all the gases are well described as the Flory-Huggins dissolution. Dilation isotherms are similar in shape to the corresponding sorption isotherms. From sorption and dilation data, partial molar volumes V(R)BAR of the dissolved gases are determined. A linear relation is found between partial molar volume and van der Waals volume V(W)BAR, i.e., V(R)BAR = 1.6 V(W)BAR + 18.5 in cm3/mol. This relation is almost the same as that between molar volume and V(W)BAR for liquid n-alkanes.