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Keywords:

  • foam shrinkage;
  • elastomer;
  • elasticity;
  • CO2 diffusivity;
  • entanglement

Abstract

A microcellular foam was prepared from a thermoplastic elastomer by a batch physical foaming with CO2. Two hydrogenated polystyrene-b-polybutadiene-b-polystyrene (SEBS) copolymers with different styrene ratios were used as an elastomer basis and blended with polystyrene (PS) to control their rigidity and gas permeability. The end-blocks of the SEBS form a physical cross-link and provide a rubber-like elasticity when cooled. SEBS alone, with its lower styrene content, cannot be physically foamed while retaining a stable-shape dimension because of its higher gas permeability and lower rigidity. SEBS with higher styrene contents were used, or the PS blend ratio was increased to 80/20 or 50/50, and batch physical foaming experiments were conducted at three temperature levels (60, 100, and 120°C) while the sorption CO2 pressure was maintained at 10 MPa. Increasing the styrene content or blending PS with SEBS increased the storage modulus and decreased the gas permeability. As a result, the shrinkage of the foam was controlled, and stable microcellular elastomer foams could be prepared. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013