Recent industry research has uncovered the core mechanism behind epoxy resin's tendency to yellow and lose luster under sunlight, providing key support for the upgrading of relevant protective technologies. Epoxy resin is widely used in coatings, adhesives, composite materials and other fields due to its excellent adhesion, chemical resistance and insulation properties, but the yellowing problem after outdoor use has long plagued the industry. Studies show that epoxy yellowing is essentially a reversible photo-oxidative degradation process initiated by UV light, with over 90% of products being "high-risk" due to their bisphenol A structure. The benzene rings in bisphenol A and the C-N bonds in amine curing agents easily absorb UV energy, leading to chemical bond breakage and the generation of highly reactive free radicals, which in turn trigger a chain reaction of hydrogen abstraction and oxidation. With the participation of oxygen, the reaction ultimately produces chromophores such as carbonyl groups that absorb visible blue light, making the material appear yellow. Conjugated carbonyl structures like quinones can exacerbate the yellowing effect. To address this pain point, the industry has developed a variety of solutions. Adding UV absorbers and light stabilizers is cost-effective and simple in process, but the dosage must be precisely controlled. Replacing bisphenol A with aliphatic epoxy resin can improve yellowing resistance, but it has drawbacks such as high cost and insufficient mechanical properties. The method of applying polyurethane or fluorocarbon protective coatings on the surface is widely used in scenarios such as outdoor floors and ship decks, but it increases construction costs. Switching to anhydride-based curing agents can effectively improve weather resistance. Experts suggest that enterprises can choose suitable solutions according to application scenarios. For high-frequency outdoor use, combining surface protection and resin modification technologies can balance effectiveness and cost. With the development of material technology, precise prevention and control of epoxy yellowing is expected to achieve new breakthroughs, further expanding its application potential in outdoor fields.
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