Such materials include, for example, polyolefin resins such as polyethylene, polypropylene; fluorocarbon polymers such as polytetrafluoroethylene; ethylene copolymers such as ethylene-ethyl acrylate copolymer and ethylene vinyl acetate copolymer; polyesters; styrene polymer or copolymers such as polystyrene, styrene-butadiene copolymer, and styrene-acrylate copolymers; higher fatty acids such as p