Exposure to solar ultraviolet (UV) radiation causes photochemical damage near the exposed surface, which results in the degradation of composite reinforcing elements. To minimise the UV degradation, epoxy polymers are being applied as protective coatings to composite materials to retain properties during their design service life. In this study, the effects of UV exposure on the physical, mechanical, and thermo-mechanical properties, including the microstructure particulate-filled epoxy-based polymer coating, were investigated. The polymer coating contains up to 60% by volume of hydrated alumina powder fire retardant (FR) and fillers such as an industrial waste like fly ash (FA) and is exposed to simulated UV conditions either 1000 h or 2000 h. Physical observations showed yellowing at the surface of neat epoxy coating after UV exposure but the presence of particulate FR and FA fillers minimised fading and weight loss. Similarly, no reduction in the flexural strength was observed for polymer coating containing at least 40% fillers, indicating that the FR and FA retained the structural performance of the coating. SEM observation revealed formation of microcracks in the surface of the neat epoxy resin but a dense microstructure in particulate filled epoxy resin after exposure to UV radiation. FTIR analyses indicated that photo-degradation due to UV radiation was limited only on the thin surface of the coating. From the results of this study, a coating thickness of at least 11 mm is required for epoxy based polymer coating with 60% by volume fillers, which is 5 times thinner than neat epoxy resin, to provide 100 years of UV resistance.

暴露于太阳紫外线（UV）辐射会在裸露的表面附近造成光化学损伤，从而导致复合增强元件的性能下降。为了最大程度地减少UV降解，将环氧聚合物作为保护性涂料施加到复合材料上，以在其设计使用寿命内保留其性能。在这项研究中，研究了紫外线对物理，机械和热机械性能的影响，包括微结构颗粒填充的环氧基聚合物涂层。聚合物涂料包含高达60％（体积）的水合氧化铝粉末阻燃剂（FR）和填料（如工业废料，如粉煤灰（FA）），并暴露于1000 h或2000 h的模拟紫外线条件下。物理观察表明，暴露于紫外线后，纯净的环氧涂料表面发黄，但是颗粒状FR和FA填料的存在使褪色和重量损失最小化。类似地，对于包含至少40％填料的聚合物涂层，未观察到弯曲强度的降低，表明FR和FA保留了涂层的结构性能。SEM观察表明，在暴露于UV辐射之后，在纯净环氧树脂的表面中形成了微裂纹，但是在填充微粒的环氧树脂中具有致密的微观结构。FTIR分析表明，紫外线辐射引起的光降解仅在涂层的薄表面上受到限制。根据这项研究的结果，含60体积％填料的环氧基聚合物涂层要求涂层厚度至少为11 mm，