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 (CO 2 ) 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 (N 2 )-assisted supercritical carbon dioxide CO 2 foaming and aging experimental results, it was found that the hexagonal cells can match the actual shrinkage process well, and no less than 50% N 2 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.