MODEL FOR THE SOLID-LIQUID PHASE-TRANSITIONS (MELTING) OF UNDILUTED RANDOM SEMICRYSTALLINE COPOLYMER OF VINYLIDENE-CHLORIDE WITH METHYL ACRYLATE MONOMERS

A comprehensive pseudoequilibrium melting model for pure random copoly mers of vinylidene chloride (VDC) with methyl acrylate (MA) monomers i s developed. The model incorporates a composition-dependent surface fr ee energy contribution to the melting point depression of these copoly mers. Total exclusion of noncrystallizable copolymer units from the cr ystal phase is assumed for this copolymer system, and this leads to a thin lamellar crystal morphology. A physical model for these crystals is shown, and a large lateral surface area relative to the volume of t he crystal is suggested. The surface to volume ratio increases with in creasing copolymer composition. The model developed in this work has a n excellent fit to experimental melting point data. A nonlinear compos ition dependence was observed for the measured melting temperatures of these copolymers, and this was well predicted by the model.