Reactive Extrusion And Microcellular Injection Molding Of PET

Polyethylene terephthalate (PET) foams have a wide range of applications due to its excellent performance-to-price ratio and special performance. The PET with high melt strength for foaming was prepared by using reactive extrusion. Microcellular injection molding process for the PET was optimized, and the ways how to improve the crystallinity of the molding specimens were also explored.The results showed that the modification PET (M-PET) was prepared with high viscosity and good fluidity when the content of MA was 0.5%. The results of a design of experiments matrices indicated that the influence order of the operating parameters on the tensile strength was:shot size> injection speed> SCF content> melting temperature> mold temperature. The large shot size, moderate SCF content and melt temperature, and low injection speed and mold temperature were favorable to produce tensile specimens with high tensile strength. The dependence of tensile strength and bending strength on weight reduction was linear. The impact strength and its specific strength of microcellular specimen both increased in comparison with those of specimen without foaming.The viscosity could be enhanced and the properties of the microcellular injection molding specimens could be changed by adding appropriate amount of nucleating agent. The results showed that the rigidity was enhanced with the improvement of the crystallinity, while some toughness was lost at the same time. It was demonstrated that the crystal structure generated during the forming process had adverse effect on cell morphologies.