Microcellular PETs with High Expansion Ratio Produced by Supercritical CO2 Molding Compression Foaming Process and Their Mechanical Properties

Abstract

Supercritical CO2 molding compression foaming is an emerging technology for preparing thick microcellular polymer sheets. In a temperature range of 245–255 °C and CO2 foaming pressure range of 5–20 MPa, the molding compression foaming behavior of polyethylene terephthalate (PET) is systematically studied. The maximum expansion ratio of the prepared PET foams is above 30, while the bubble size is only ≈20 μm. It is observed that during the foaming process, the temperature drop caused by rapid depressurization reaches up to 57 °C, which greatly changes the viscoelasticity of PET and limits its foaming behavior. The nucleation and bubble growth behavior of PET is simulated and analyzed based on this change in viscoelasticity. Microcellular PET foams have excellent compression performance due to their smaller cell size and thinner cell wall, and the compression elastic modulus of the prepared microcellular PET sample is twice that of the extrusion foaming PET sample with a similar expansion ratio.