a 0 . 005 - 0 . 020 inch thick thermoplastic sheet containing 20 - 80 weight percent metal alloy biocide particulate , such as 50 micron copper powder , protects submarine structures from adhesion of flora and fauna . the sheet is isotropic and inelastically deformable in the plane of the sheet . the sheet is heated to form and adhere it to the ship hulls and the like . an intermediate lower melting point film and other aids are employed in the adhering step . heating of the sheet prior to the adhering process minimizes liberation of environmentally harmful volatiles . the sheet is removable by heating , so the material may be recycled .