Polymeric Materials for Use as Binders and Transparent Films.

摘要

Significant improvements have been made in the ultraviolet stability of silicone coatings. Purified octamethylcyclotetrasiloxane was converted to pure poly(dimethylsiloxane), and coatings made from this polymer were cured with gamma radiation or chemical reagents. The change in absorption of the gamma-cured coating upon ultraviolet irradiation was significantly less than that of any previously prepared coating. As far as is known, this is the best ultraviolet radiation-resistant silicone coating available. The change in absorption of the chemically cured coating was almost the same as that of the gamma-cured coating. In addition, commercial poly(dimethylsiloxane) was purified by gel filtration and by column chromatography. A coating from commercial poly(dimethylsiloxane) purified by column chromatography with neutral alumina experienced less change in absorption upon ultraviolet irradiation than any previously prepared coating, but a greater change than the pure poly(dimethylsiloxane) coatings above. Improvements have also been made on infrared-transparent coatings. Curing of a high viscosity hexafluoropropylene-vinylidene fluoride copolymer, which previously required heating, has been accomplished at room temperature with benzoyl peroxide plus 1, 4-diazabicyclooctane without changing the infrared transmission of the coating.