Microcellular morphology evolution of polystyrene/thermoplastic polyurethane blends in the presence of supercritical CO ₂

In this article, a facile melt blending and solid batch foaming approach was proposed to prepare microcellular polystyrene/thermoplastic polyurethane (PS/TPU) blending foams with supercritical carbon dioxide (CO ₂ ). Compared with those of pure PS and pure TPU, an interesting phenomenon about the enhanced complex viscosity and storage modulus, as well as decreased loss factor of PS/TPU blends, was found. The solubility of CO ₂ in the PS/TPU blends was enhanced, owing to the CO ₂ solubilization effects of TPU. An interesting bimodal cell structure (BCS) was observed in the PS/TPU blending foams with the TPU content of 10, 15, and 20%. Consequently, a significant conclusion could be speculated that the generation of BCS in the PS/TPU blending system depended on not only the viscosity and morphology of the polymer blends but also the solubility and diffusivity of the CO ₂ as well as the type of cell nucleation. The thermal insulation property of PS foam was improved by the introduction of TPU.