Foam extrusion characteristics of thermoplastic resin with fluorocarbon blowing agent. III. Foam sheet extrusion of polystyrene and low‐density polyethylene

An experimental study was conducted on the extrusion of polystyrene and low‐density polyethylene foam sheets, using fluorocarbon blowing agents and a tubular die. The effects of the type and concentration of blowing agent, die temperature, and takeoff speed on foam extrusion characteristics were investigated. They are foam density, tensile modulus, and cell morphology. It has been found that die temperature greatly influences the open cell fraction and foam density and that the takeoff speed greatly influences cell orientation, which, in turn, has a profound influence on the tensile modulus of the foam sheets produced.