Modification of styrene-acrylic emulsion by organic UV absorber in synergy with fluorine and silicon monomers for weatherable coatings

To improve the weather ability and thermal stability of styrene-acrylic polymer emulsion coatings, a series of novel styrene-acrylic polymer emulsion modified with 2-[2-hydroxy-5-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole (HMEB), hexafluorobutyl methacrylate (HFMA), and vinyl-trimethoxysilane (VTMS) were prepared through semi-continuous seed emulsion polymerization. The emulsions and their coatings were characterized by Fourier transform infrared spectroscopy, ultraviolet absorption spectroscopy (UV-Vis), X-ray photoelectron spectroscopy, dynamic laser scattering, transmission electron microscopy, zeta potential, thermogravimetric analysis, and artificially accelerated aging test. According to the results, the new polymer emulsion had superior UV absorption from 308 to 364 nm. Moreover, the coating performed the best anti-aging stability when the content of HMEB, HFMA, and VTMS reached 4%, 2%, and 3%, respectively. After the 1000 h aging test, the color difference (ΔE) and rate of loss of gloss (ΔG) were only 6.86% and 51.10%, while the unmodified coatings were 16.05% and 72.22%, respectively. Furthermore, the thermal stability and water resistance of the coating were improved by fluorine and silicon monomers. The initial decomposition temperature was increased from 327 to 339°C. Moreover, the UV stabilization mechanism is preliminarily discussed.