Photochemical stability of partially fluorinated acrylic protective coatings. Part 3. Copolymers of 1H,1H,2H,2H-perfluorodecyl acrylate and 2,2,2-trifluoroethyl methacrylate with butyl methacrylate

Copolymers of 2,2,2-trifluoroethyl methacrylate, or 1H,1H,2H,2H-perfluorodecyl acrylate (XFDA) and butyl methacrylate (BMA) have been irradiated in air under artificial solar light and their photo-oxidative stability has been investigated. Molecular and chemical changes occurring during the treatments have been monitored by weight loss and gel content determination, size exclusion chromatography and FTIR spectroscopy. It has been determined that the overall behaviour of both copolymers is controlled by the BMA units, independently of the total fluorine content. The photo-ageing takes place mainly via the mechanism of oxidation of methacrylic polymers containing long side ester groups, whose flexibility favours macroradical coupling reactions. The tendency to crosslink is balanced only in the case of the initial stages of degradation of XFDA/BMA by the scission reactions derived from the direct attack of oxygen on the fluorinated acrylic units.