Method for making a corrugation-free foam and foams made by the method

摘要

A method is disclosed for extruding a corrugation-free polystyrene foam with 100% carbon dioxide as the blowing agent, by extruding the extrudate through an annular die opening 38 so that it contacts a choke ring inner surface 31. A foam made by the method will have no visible corrugations and an average cell size of 0.20 to 0.35 millimeter.