MISCIBILITY OF POLY(METHYL METHACRYLATE) BLENDS WITH HALOGEN-CONTAINING POLYCARBONATES AND COPOLYMERS

Blends of poly(methyl methacrylate) (PMMA) and bisphenol-A polycarbonate (PC) having high molecular weights do not form homogeneous mixtures at equilibrium above the glass transition temperature. In this paper, the possibility of developing blends of PMMA with polycarbonates that can be melt processed into homogeneous materials was examined by adding a comonomer to the polycarbonate. Hexafluorobisphenol-A appears to be an extremely effective comonomer for this purpose. The phase behaviour of PMMA blends with hexafluorobisphenol-A polycarbonate (HFPC) and with PC-HFPC copolycarbonates containing various amounts of hexafluorobisphenol-A was determined. The blends of PMMA and HFPC are miscible and do not phase separate prior to thermal decomposition. The phase separation temperatures of PMMA blends with the copolycarbonates increase dramatically as the hexafluorobisphenol-A content increases. Blends of PMMA with copolycarbonates containing 15 wt% hexafluorobisphenol-A or higher have phase separation temperatures above the temperature range required for melt processing. Additionally, the interaction energies for blends of PMMA with PC, bisphenol chloral polycarbonate and PC-HFPC copolymers were calculated from the phase boundaries using the lattice fluid theory and binary interaction model.