Among the thermoplastic materials which may be employed in the practice of this invention are cellulose esters, such as cellulose acetate, 4cellulose propionate, cellulose butyrate, cellulose nitrate, cellulose acetate-butyrate or cellulose acetate-propionate; cellulose ethers such as ethyl cellulose or benzyl cellulose; extrudable polyamides such as nylon; polyesters such as polyethylene adipate