Interrelationship between the crystallization behavior,injection molding conditions,and morphology of poly(ethylene terephthalate)/poly(methyl methacrylate) alloys

The thermal and isothermal crystallization behavior of PET/PMMA (poly(ethylene terephthalate)/poly(methyl methacrylate)) alloys was investigated. The crystallization of PET is accelerated significantly by alloying with PMMA. As a result, crystalline specimens could be injection molded with the alloy at low mold temperatures of 19°, 55° and 90°C., whereas a mold temperature of about 130°C is normally required for crystallinity to develop in the virgin PET grade. The impact strength of the alloy specimens increased significantly with decreasing mold temperature despite a comparable degree of crystallinity. The increase in impact strength is correlated to the reduction in the crystallite size and broadening of the crystal size distribution with decreasing mold temperature.