Corrugated thermoplastic polyurethane foams with high mechanical strength fabricated by integrating fused filament fabrication and microcellular foaming using supercritical CO2

Thermoplastic polyurethane (TPU) has been widely implemented in many fields due to its good elasticity. Microcellular foaming not only can achieve weight reduction, but also can enhance the elasticity of TPU products. However, the enhancement of elasticity by foaming is limited, while the introduction of corrugated structures can significantly improve the elasticity of TPU foams. Considering the difficulties to produce TPU parts with corrugated structures for conventional processes, fused filament fabrication (FFF) combined with microcellular foaming was developed to fabricate TPU foams with high elasticity. An FFF 3D printer was used to prepare solid TPU samples with corrugated structures, and microcellular foaming was used to fabricate foamed TPU samples. As expected, the corrugated structures have been successfully and precisely preserved in the obtained TPU foams, and further, the TPU foams have expansion ratio of more than 7 and cell density of higher than 1012 cells/cm3. Thanks to the corrugated structures and refined cellular morphology, the 7.09 expanded TPU foams exhibited outstanding compressive properties with an energy loss coefficient of 28% and a maximum stress of higher than 0.25 MPa. It is further found that introducing the corrugated structures or enlarging cell sizes could improve the elasticity and buffering performance of TPU foams.