Microstructures and fracture behavior of glass-fiber reinforced PBT/PC/E-GMA elastomer blends - 1: microstructures

A group of glass-fiber-reinforced polymer composites with controlled morpho logy were designed and prepared by sequential compounding of poly(butylene terephthalate)/glass-fiber (PBT/GF) composite with a reactive elastomer, et hylene-co-glycidyl methacrylate (E-GMA), and/or polycarbonate (PC). The mic rostructures of the composites were characterized by means of AFM, SEM and thermal analysis. The results indicate that the glass fiber was surrounded by a dead layer of PBT. In the matrix, the E-GMA particles, of sizes varyin g between 0.5 and 1 mum, were encapsulated by the PBT phase. The PBT and PC formed an interconnected phase structure with a PBT domain thickness of ab out 1 mum and the PC domain thickness of less than 0.5 tm. It was found tha t when the PBT/GF was mixed with the E-GMA in the first step of the sequent ial blending, the epoxide groups in the E-GMA tended to homo-polymerize thr ough ring-opening rather than to react with the carboxyl and/or hydroxyl gr oups of the PBT. Consequently, a slightly cross-linked structure formed in the E-GMA phase, which kept the E-GMA domains to stay in the PBT phase duri ng the second step of the sequential blending with the PC. On the other han d, the transesterification between the PBT and the PC resulted in a decreas e in the PBT chain regularity, leading to a lower crystallization rate and formation of crystallites with low perfection. (C) 2001 Elsevier Science Lt d. All rights reserved.