Research on the cyclic compression performance of polycarbonate-based thermoplastic polyurethane foams prepared by microcellular foaming

Polycarbonate-based thermoplastic polyurethane (TPU) is an advanced thermoplastic elastomer that has excellent yellowing, oxidation and corrosion resistances, as well as outstanding mechanical properties. Polycarbonate-based TPU foams have potentially important applications in sport goods, biomedical, and chip polishing fields. In this study, two microcellular foaming strategies including Heating-Foaming (H-foaming) and Cooling-Foaming (C-foaming) with carbon dioxide as blowing agents were proposed to prepare structure-tunable polycarbonate-based TPU foams. Firstly, TPU foams with similar cellular morphology were prepared by H-Foaming and C-Foaming, and they were used to explore the effect of foaming strategy on the cyclic compression properties of the TPU foam. Secondly, TPU foams with the same expansion ratio but with different cell sizes were prepared by H-Foaming, which were further used to explore the effect of cell sizes on the cyclic compression properties of the TPU foam. Thirdly, TPU foams with similar cell size but with different expansion ratios were prepared, and they were used to explore the dependences of the cyclic compression properties on the expansion ratio of TPU foams. It was found that the compression strength of the TPU foam prepared by C-Foaming can be enhanced by more than 15%, in comparing with that of the TPU foam prepared by H-Foaming. Furthermore, it was demonstrated that the expansion ratio of TPU foam is the key structural factor in determining its compression strength. The compression strength reduced from 5.91 to 0.17 MPa with the expansion ratio increasing from 0 to 7.2. Reducing cell size leads to enhanced compression strength but deteriorated compression resilience. Increasing expansion ratio will firstly deteriorate and then benefit the compression resilience.