Modified graphene quantum dots as efficient UV stabilizers for aromatic polyurethane acrylate coatings

Solar Ultraviolet (UV) radiation significantly reduces the service life of aromatic polyurethane-based coatings by causing yellowing, loss of adhesion and deterioration of dynamic mechanical properties. Therefore, incorporating effective UV stabilizers is essential to improve the resistance of such coatings against UV aging. In this study, vinyltrimethoxysilane-modified graphene quantum dots (VGQD) were synthesized and employed as UV stabilizers in aromatic polyurethane acrylate coatings to enhance their resistance to accelerated UV aging. Characterization results revealed that the coatings containing 0.3 wt% and 0.5 wt% VGQD exhibited strong fluorescence emission at 472 nm, intense UV absorption in the 280 to 400 nm range, and excellent UV-A blockage (91.8–97.3%). Whereas the neat coating showed neither fluorescence emission nor significant UV absorption above 280 nm. After exposure to accelerated UV aging, the VGQD-containing coatings displayed considerably lower surface roughness and less color change compared to the blank coating. Moreover, the loading of VGQD markedly improved adhesion strength and preserved dynamic mechanical properties. UV aging led to a notable reduction in storage modulus, Tg and crosslink density in all samples; however, the extent of degradation was most pronounced in the neat coating and decreased in the presence of VGQD.