Experimental aspects of compatible polymer mixtures

Abstract

Recent investigations on the possible applications of thermodynamic concepts to experimental studies of polymer mixtures by using the phase diagram are presented. Phase separation behavior may be classified into three categories, namely amorphous-amorphous polymer, crystalline-amorphous polymer, and crystalline-crystalline polymer mixtures. In the theoretical part of this paper, Scott's treatment of polymer mixtures based on the classical Flory-Huggins equations are used to calculate the spinodal, binodal, and melting point depressions. In the case of amorphous-amorphous polymer mixtures, phase diagrams were gathered from the literature. Lower critical solution temperature type phase diagrams for polystyrene-poly(vinyl methyl ether) were introduced and analyzed. As to the phase separation behavior, both spinodal decomposition and nucleation and growth mechanisms were observed. For crystalline-amorphous polymer systems, crystalline polymer melting point depressions were analyzed for a poly(vinylidene fluoride)-poly(methyl methacrylate) mixture. Radial growth rates of crystalline polymer in the mixtures were well described by extending the recent Lauritzen-Hoffman theory for homopolymers to polymer mixtures. For crystalline-crystalline polymer systems, the possibility of eutectic solidification was predicted.