thermoplastic surface modification is achieved with photocatalysts , such as titanium dioxide , tungsten oxide and mixtures thereof . a uniform coating of a powdered photocatalyst is applied to a thermoplastic surface that is wetted with an organic solvent . the coating is in a range between approximately 1 . 5 mg / cm 2 to approximately 2 . 5 mg / cm 2 . after the uniform coating of photocatalyst is dried , the thermoplastic surface is heated to a temperature above its softening temperature , usually in a range between approximately 80 ° c . to approximately 130 ° c . ; then , a mild pressure is applied to imbed the photocatalyst into the surface of the thermoplastic sheet . the method of modification is inexpensive , long - lasting and non - detrimental to the thermoplastic surface . a surface is provided with improved aesthetic appearance , extended lifetime and sustained protection from undesirable growth of nuisance organisms , such as algae , fungus , bacteria , mold , mildew and the like .