EFFECT OF PARTIAL MISCIBILITY ON THE MODULUS OF POLYCARBONATE POLY(STYRENE-CO-ACRYLONITRILE) BLENDS/

The composition of conjugate phases in blends of polycarbonate, PC, an d poly(styrene-co-acrylonitrile), PSAN, was calculated with the aid of observed glass transition temperatures. Solubility of PSAN (or PC) in the PC-rich (or PSAN-rich) phase increases with decreasing volume fra ction of PC (or PSAN) in blends. With regard to literature data, this trend is qualitatively explained as a consequence of the polydispersit y of components because only the fractions with lower molar mass can b e exchanged between the conjugate phases. As the modulus of conjugate phases in heterogeneous blends cannot be measured, it is approximately estimated as that of the blends containing 10-15 vol% of totally misc ible minority component. Positive deviation of the moduli of partially miscible blends, which are compared with theoretical values calculate d by using the equivalent box model combined with percolation approach , is ascribed to the fact that moduli of conjugated phases are higher than those of parent polymers. The increased modulus of conjugate phas es is interpreted as a result of suppressed molecular mobility due to associative interactions between the chains of components in both pres ent phases.