. . . . "Exemplary thermoplastic materials include cellulose esters, e.g., cellulose acetate, cellulose propionate, cellulose butyrate; mixed esters of cellulose; cellulose ethers, e.g., ethyl cellulose; nylon and polymeric materials, e.g., polyvinyl alcohol acetals, polyvinyl chloride, polyvinyl chloride acetate, polystyral, methyl methacrylate, polyethylene, polypropylene, and other polyolefins which may" .