Morphology development and crystallization behavior of a poly(ethylene terephthalate)/polycarbonate blend

The morphology development and crystallization behavior of an extruded poly(ethylene terephthalate)/polycarbonate blend were studied with optical microscopy, light scattering, and differential scanning calorimetry (DSC). During annealing at 280 degrees C, liquid-liquid phase separation via spinodal decomposition proceeded in a melt-extruded specimen. After the formation of the domain structure, the blend slowly underwent phase homogenization by transesterification between the two polymers. The specimen, annealed for various times (t(s)'s) at 280 degrees C, was subjected to a temperature drop to 180 degrees C for the isothermal crystallization, and then the effects of liquid-phase changes on crystallization were investigated. The crystal growth rate decreased with t(s). The slow crystallization with a large t(s) value was associated with the composition change of the separated phases and the change of the sequence distribution in the polymer chains during annealing. The influence of t(s) on the endothermic behavior of the samples was examined. As t(s) increased, the recrystallization rate was retarded during the DSC scan, displaying multiendothermic behavior. The DSC data also suggested that the increased level of transesterification would give rise to a higher number of species being rejected from the primary crystals, leading to enhanced secondary crystallization. (c) 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2220-2225, 2006