Preparation and properties of thermoplastic polyurethane foams with bimodal structure based on TPU/PDMS blends

It is still challenging to fabricate polymer foams with bimodal structure via a simple technique in the both industrial and academic fields. In this work, by mixing polydimethylsiloxane (PDMS) into thermoplastic polyurethane (TPU) and utilizing the difference of foaming dynamics between TPU and PDMS, the target foams with bimodal structures were successfully prepared through a one-step foaming process. It was shown that under the optimal conditions (i.e. PDMS content of 15 wt%, foaming temperature of 100 °C and foaming pressure of 13.8 MPa), the resultant foam possessed distinct bimodal structures with large cells of ~12 µm and small cells of ~3 µm. Such bimodal structures also help the forms to have the excellent compress strength and modulus of 506 kPa and 1618 kPa, which are much higher than the foam with uniform structure. In addition, bimodal structure foam has ~3 dB higher sound insulation than uniform structure foam.