Preparation of expanded polymers

Abstract

Abstract Cellular thermoplastic material is prepared by heating thermoplastic material mixed with discrete particulate matter to above the softening point of the thermoplastic material under pressure of a gas soluble in and essentially saturating the thermoplastic material, and extruding the resultant composition into a zone of lower pressure under conditions such that the thermoplastic material is super-saturated with respect to the gas, the discrete particulate matter having a thermal conductivity of 0.001 to 1.0 (cal) (cm.)/(sec.)(cm.sq.) ( DEG C.) and a specific heat of 0.003 to 0.3 cal/g., whereby the gas leaving solution nucleates at the sites of the said particulate matter. The particulate matter may be a metal such as lead, silver, zinc, tin, mercury, aluminium, copper, palladium and bismuth, an alloy such as Wood's metal and molybdenum-Permalloy and a metal compound such as an acetate, halide or oxalate which decomposes to the metal. Suitable thermoplastic material is that obtained by polymerizing or copolymerizing compounds such as ethylene, propylene, vinyl chloride, styrene and methylmethacrylate. The gas soluble in the thermoplastic material may be argon, nitrogen, helium, air and carbon dioxide. Wire may be covered with the cellular material using a wire covering crosshead attached to the extruder (see Division B5).

Inventors

• 👤 Ralph H Hansen

Bibliographic Details