Extrusion Foaming Of Poly (Ethylene Terephthalate) Blown With Carbon Dioxide

Poly(ethylene terephthalate) (PET) foams have a wide application prospects due to their good mechanical, thermal and recyclable characteristics. However, extrusion foaming is inadaptable for fabrication of PET foams from ordinary PET resin due to their high processing temperatures and low melt strength at the processing temperatures.In this work, reactive extrusion followed with solid-state polycondensation were adopted for ordinary PET to improve its viscoelasticity. The modified PET with high melt strength has intrinsic viscosity of higher than 1.5 dL/g and melt flow index less than 3g/10min. It's rheological behavior also shows higher viscoelasticity than ordinary PET, and it's DSC traces upon heating shows two melting peaks, indicating that the modified PET has branched structure of macromolecular chains.Extrusion foaming blown with CO2 was applied for the modified PET. The results showed that the proper die temperature facilitated improving cell morphology of PET foams. With increasing the gas inlet, cell density increased and cell size decreased significantly in the meanwhile. Nucleating agent had an evident heterogeneous nucleation effect on the foaming process. High content of the nucleating agent and the high gas inlet should be matched with each other so that PET foams with small size and uniform cell distribution could be fabricated. In this work, the liner PET foams were produced continuously and steady, with the apparent density of 0.146 g/cm3, cell density of 9×105 cells/of cell density and average cell size of 100-200μm.