The microcellular foaming of chain-extended polyethylene terephthalate (CPET) by crystallization induction method was reported in this article. The crystallization behaviors of various polyethylene terephthalate (PET) samples which were affected by the combined effect of pyromellitic dianhydride, Surlyn, and CO2 were investigated. After Surlyn was added to CPET, the crystal nucleation of various CPET samples was improved, and numerous but small spherulites were generated. Two kinds of CPET samples with the content of 0 phr and 1 phr Surlyn were foamed at various temperature by batch foaming method. Changing the saturation temperature could adjust the appearance of high-temperature melting crystals which would affect the final cellular structures in various CPET foams. With the decrease of saturation temperature, the cell size decreased while cell density increased. At the saturation temperature of 265°C and 250°C, the cell density of CPET foam with Surlyn was one magnitude larger than CPET foam without Surlyn. At the saturation temperature of 247°C, the microcellular PET foams with the cell density of 109 cells cm−3 and the cell size less than 10 µm had been developed successfully.
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