Preparation of low density microcellular thermoplastic polyurethane with high compression properties based on micro-phase separation structure

Abstract

A new foaming strategy was proposed to prepare microcellular thermoplastic polyurethane (TPU) with high volume expansion ratio, low shrinkage and stable mechanical properties at low temperature by modulating micro-phase separation structure of TPU through the synergistic effect of water as co-blowing agent and polytetrafluoroethylene (PTFE). Molecular dynamics simulation was conducted to screen co-blowing agent (water) interacted well with CO2 and TPU. The interaction of water and CO2 improved the solubility of blowing agents in TPU. The hydrogen bond interaction between water and TPU regulated the arrangement of soft/hard segments and micro-phase separation structure. The volume expansion ratio of microcellular TPU at 100 °C and 15 MPa increased from 4.0 to 9.0 when the water content was 5 wt%. The synergistic effect of water and PTFE improved the regularity of the hard segment. The water and in-situ fibrillated PTFE significantly improved the initial expansion ratio of microcellular TPU and effectively reduced the shrinkage. Eventually, microcellular TPU with 6.5-fold was prepared at 100 °C and its mechanical properties was evaluated.