For example, polymers and copolymers of a-olefins such as high density polyethylene, polypropylne or ethylene propylene copolymers ,of polytmethyl-pentene-l, of polyesters such as polyethylene terephthalate and polyethylene-1,2-di-phenoxy ethane,4,4- dicarboxylate, and of the various nylons may be processed.