Antishrinking Strategy of Microcellular Thermoplastic Polyurethane by Comprehensive Modeling Analysis

A comprehensive model for shrinkage behavior of soft thermoplastic polyurethane (TPU) elastomer foams has been built, which involves in situ tensile testing of TPU under different carbon dioxide (CO2) plasticization pressures and antishrinking abilities of different cell shapes of circular, square, and hexagonal evaluated by a three-order Ogden hyperelastic equation. Combined with the nitrogen (N2)-assisted supercritical carbon dioxide CO2 foaming and aging experimental results, it was found that the hexagonal cells can match the actual shrinkage process well, and no less than 50% N2 content remaining in cells can effectively improve the antishrinking ability of TPU foams. According to the principle that there is no pressure difference between inside and outside foam, a feasible method of aging TPU foam under a variable ambient vacuum to reduce the shrinkage ratio was proposed, simulated, and proved.