Expanded polypropylene sheet for thermoforming - by extruding a compsn. contg. polypropylene, blowing agent and nucleating agent through a sheet die

摘要

Expanded polypropylene or ethylene propylene copolymer sheets are made by extruding a compsn., comprising polypropylene, a blowing agent and a nucleating agent, through a sheet die without cooling on leaving the die. The sheet may be compacted lightly through rollers after extrusion to give a smooth surface. The new sheets are generally 0.7-1.3 mm.thick, with a density of 0.65-0.75, and are esp. useful for vacuum forming. The sheets have improved tensile strength and high chemical inertness.