Miscibility and phase behaviors in PVC / acrylate copolymer blends

Abstract

Miscibility and phase behavior in blends of poly(vinyl chloride)[PVC] with poly(methyl-co-hexyl acrylate)[MHA] or with poly(methyl-co-2 ethyl hexyl acrylate) [MEH] were studied. It was found that both blend systems, PVC/MHA and PVC/MEH, exhibited LCST behavior and had a miscibility window. By applying the mean field theory to the composition-composition diagram [C-C plots] of MHA copolymer blend system and temperature-composition diagram [T-C plots] of PVC/MHA or PVC/MEH blend system, segmental interaction parameters which represent the binary interaction between three different monomer units, were estimated. The calculated segmental interaction parameters reflect that miscibility windows observed for PVC/MHA and PVC/MEH copolymer blend systems, were attributed to the effect of repulsion between methyl acrylate and hexyl acrylate (or 2 ethyl hexyl acrylate) units within the copolymer. By using the calculated segmental interaction parameters, blend interaction parameters $\chi_{\mbox{blend}}$ for the PVC/MHA and PVC/MEH blend systems were calculated as a function of copolymer composition according to the temperature. As the temperature increased, the values of $\chi_{\mbox{blend}}$ increased and the miscible region of $\chi_{\mbox{blend}}<\chi_{\mbox{blend}}^{\mbox{crit}}$ was reduced. Above results describe the LCST behavior of these blend systems quantitatively. To investigate the effect of specific interaction on the miscibility for these blend systems, it was also attempted to describe blend interaction parameter as a function of polar group concentration in the acrylate copolymer. The blend interaction parameter values exhibited U-shape curve as a function of weight fraction of C=O groups in the copolymer, which was related to the specific interaction between the acrylate carbonyl groups and methine protons of PVC. The miscibility behavior in copolymer-copolymer blend system of poly (vinyl chloride-co-vinyl acetate) [PVC-VAc] with poly(methyl-co-hexyl acryl...