Interaction Parameters and Heats of Dilution for Ethylene Propylene Rubber in Various Solvents

Crosslinked ethylene propylene rubber gels were swollen in five solvents at 25–100° C. The solvent polymer interaction parameter μ for each system was determined as a function of temperature and polymer concentration. A thermodynamic criterion of the sign of the heat of dilution, ΔH1, was pointed out. For three of the systems ΔH1 was negative. The entropy contribution to the interaction parameter was found to be smaller than usual for systems having a temperature-dependent heat of dilution. The heats of dilution and the entropy terms may be consistently interpreted in terms of Prigogine's theory of solutions.