Miscibility in blends of poly(vinyl chloride) and chlorinated poly(vinyl chloride) with polycarbonates/

Abstract

Blends of aromatic polycarbonates with poly(vinyl chloride) (PVC) and chlorinated poly(vinyl chloride) (CPVC) have been investigated. The polycarbonates include homopolymers and copolymers based on bisphenol-A derivatives. Polycarbonate/polycarbonate blends were also studied. The primary method for studying miscibility was differential scanning calorimetry. Dynamic mechanical analysis and infrared analysis were also utilized. Blends of high molecular weight bisphenol-A polycarbonate (BPC) and tetramethylbisphenol-A polycarbonate (TMPC) were found miscible in all proportions at temperatures exceeding 300$\\sp\\circ$C. The phase behavior of BPC blended with tetrachlorobisphenol-A polycarbonate (TCPC) was found to depend strongly on the molecular weight of the homopolymers. Low molecular weight blends exhibit LCST behavior. The remaining binary combinations of BPC, TMPC, TCPC, hexafluorobisphenol-A polycarbonate (HFPC), and tetrabromobisphenol-A polycarbonate (TBPC) form two-phase blends at all blend compositions between 20 and 80% by weight. TCPC forms single-phase blends with PVC. Annealing temperatures up to 240$\\sp\\circ$C did not affect phase separation in these blends. Infrared analysis in the carbonyl stretch region does not implicate the carbonate group as a significant factor affecting miscibility in these blends. Dynamic mechanical analysis shows that the two polymers retain their own secondary relaxations. TCPC is also miscible with solution-chlorinated PVCs (solution-CPVCs) having chlorine contents up to 70.2 weight percent, by weight, chlorine. Slurry-chlorinated PVCs were also miscible with TCPC. TBPC appears to be miscible with PVC and CPVCs, though it shows more an affinity for the chlorinated PVCs. Miscibility in these blends is favorable interactions with vinyl chloride monomer and/or a repulsive, intramolecular copolymer effect within the solution-CPVC. Segmental interaction parameters, $X\\sb{\\rm ij},$ were estimated using a binary interaction, mean field theory which can be applied to miscibility data from copolymer-containing blends. The boundaries of miscibility windows in polycarbonate-copolymer/solution-CPVC blends were used to calculate $X\\sb{\\rm ij}$'s. Miscibility windows were shown to be sensitive to small changes in the $X\\sb{\\rm ij}.$