Crystallization of hard segment domains with the presence of butane for microcellular thermoplastic polyurethane foams

This paper presents the effects of dissolved butane on the crystallization of hard segment (HS) and its effects on enhancement of cell nucleation to manufacture microcellular thermoplastic polyurethane foams (TPU). The TPU samples were first reprocessed by melt compounding through a twin-screw extruder. A broad distribution of HS domains was generated after this processing, including some perfected HS nano-crystals with a higher melting temperature. In addition to the processing effect, the saturation temperature and the plasticizing butane significantly induced a larger number of HS crystalline domains. Consequently, cell nucleation was significantly promoted in the vicinity of the largely distributed HS crystalline domains over a wider saturation temperature range of 150 °C-170 °C at a saturation pressure of 55 bar.