Studies on the Interaction Parameter in Polysiloxane Solutions

Abstract

The thermodynamic properties of solutions of polydimethylsiloxane and silicon resin in non-polar solvents have been studied in a moderate concentration range at temperatures from 26 to 40°C. Applying Flory's theory, the interaction parameter x1 was calculated from the activity of solvent, which was determined from the lowering of its vapor pressure. It was found that the value of x1 and its temperature dependency are characteristic of the interaction of polysiloxane with solvent. The heat term (JWh) and the entropy term (JW.) in x1 were calculated from the temperature dependency of x1 at the average temperature. It was confirmed that the obtained relation between JWh and JW. is represented by a smooth curve, independent of concentration and solvent which goes nearly through the origin.