Open-Cell Microcellular Foams From Thermoplastic Polyester Elastomer/Ethylene-Vinyl Acetate Blends: Insights Into Structure Formation and Properties

Open-cell polymer foams are highly valued for their exceptional shrinkage resistance and energy absorption properties, making them promising for advanced practical applications. However, fabricating open-cell foams from polymeric materials remains a significant challenge. In this study, thermoplastic polyester elastomer (TPEE)-based microcellular foams with high open-cell content (OCC) and low shrinkage were successfully prepared by blending TPEE with a specified proportion of ethylene-vinyl acetate copolymer (EVA) and employing supercritical carbon dioxide (scCO2) as a physical blowing agent. Experimental results revealed that TPEE and EVA exhibit good compatibility during melt blending. Furthermore, due to the difference in melt strength between TPEE and EVA under identical temperature and pressure conditions, TPEE undergoes normal foaming, while EVA, having lower melt strength, experiences excessive biaxial stretching. This leads to the rupture of the cell walls in TPEE, significantly increasing the OCC. The resultant TPEE/EVA microcellular foam achieved an impressive OCC of 90.6% and a shrinkage rate below 5.0%. In contrast, the pure TPEE microcellular foam exhibited an OCC and shrinkage rate of 66.0% and 54.9%, respectively. Compression cycle tests further demonstrated that the energy absorption performance of the TPEE/EVA open-cell foam surpasses that of the TPEE microcellular foam.