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 morphology were designed and prepared by sequential compounding of poly(butylene terephthalate)/glass-fiber (PBT/GF) composite with a reactive elastomer, ethylene-co-glycidyl methacrylate (E-GMA), and/or polycarbonate (PC). The microstructures 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 varying between 0.5 and 1 μm, were encapsulated by the PBT phase. The PBT and PC formed an interconnected phase structure with a PBT domain thickness of about 1 μm and the PC domain thickness of less than 0.5 μm. It was found that when the PBT/GF was mixed with the E-GMA in the first step of the sequential blending, the epoxide groups in the E-GMA tended to homo-polymerize through ring-opening rather than to react with the carboxyl and/or hydroxyl groups 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 during the second step of the sequential blending with the PC. On the other hand, the transesterification between the PBT and the PC resulted in a decrease in the PBT chain regularity, leading to a lower crystallization rate and formation of crystallites with low perfection.