THE EFFECT OF MOLAR VOLUME ON THE SWELLING OF POLY(DIMETHYLSILOXANE) IN FLUOROCARBON FLUIDS

The vapour sorption of three fluorocarbon fluids (tetrafluoroethane, c hlorotetrafluoroethane, and heptafluoropropane) has been measured in c rosslinked and uncrosslinked poly(dimethylsiloxane) as a function of t he temperature in the interval 35-105 degrees C. For a given solvent, the swelling activity parameter, S, for the solvent/crosslinked polyme r system decreases as both the degree of swelling and the temperature increase. The range of experimental conditions examined allowed consid eration of S for different solvents, but constant molar volume, V-1. P lots of S as a function of degree of swelling can be reduced to famili es of curves at constant V-1 for the three solvents studied here. The dependence of S on solvent quality and temperature is then encompassed in its variation with V-1.