DIFFERENTIALLY EXPANDED SHEET MATERIAL

摘要

A process for the manufacture of a differentially expanded sheet material comprises applying an organic solvent to the surface of an expandable thermoplastic sheet containing a blowing agent and allowing the treated sheet to at least partially dry before a composition containing a metallic powder and a kicker for the blowing agent is applied to selected areas of the treated surface. The sheet is then uniformly heated to a temperature at which the blowing agent in contact with the kicker decomposes but below that at which it decomposes in the absence of the kicker, so that the areas of the sheet in contact with the kicker expand to a greater extent than the uncontacted areas.