This study investigated the effects of dissolved CO2 on the crystallization of hard segment (HS) to generate double crystal melting peak for expanded thermoplastic polyurethane (ETPU) bead foam manufacturing. The double crystal melting peak is generated while annealing at elevated temperatures in a autoclave-based ETPU foaming process. The influence of saturation temperature, time, and pressure on the generation of double melting peak structure in TPU was investigated. It was observed that higher saturation temperature assisted in the improvement in the size and perfection of the smaller HS crystals and resulted in formation of double melting peak close to the melting point of TPU. However, the saturation pressure was the most critical parameter to enhance the double melting peak. Furthermore, in the presence of dissolved CO2, the saturation temperature required to generate the double melting peak in the TPU decreased significantly due to the plasticization effect of CO2. The longer saturation time increased the amount of perfected HS crystals with a high melting temperature.
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