PHASE MICROHETEROGENEITY IN BISPHENOL-A POLYCARBONATE POLY(METHYL METHACRYLATE) BLENDS/

The controversial equilibrium phase behaviour in the blend system of p oly(methyl methacrylate) and bisphenol-A polycarbonate was re-examined by using differential scanning calorimetry, optical and scanning elec tron microscopy. This study has shown that the 'transparent' blends of PC/PMMA actually displayed micro-heterogeneity, with domain sizes of ca. 100-300 Angstrom. The micro-heterogeneous domains were so small th at the blends exhibited a single glass transition point (T-g) and appe ared transparent. Upon heating above the T-g of the matrix components of the blends, the original micro-phase domains suddenly expanded at 1 80 degrees C, increasing rapidly to about 1-3 mu m in size, with incre ased cloudiness. This present study has also shown that the 'transpare nt' blends when heated above 240 degrees C also displayed micro-phase separation. Consequently, the phase behaviour in the PC/PMMA blends ar e re-interpreted from kinetic points of view. Copyright (C) 1996 Elsev ier Science Ltd.