UV epoxy resin solution to yellowing problem

lencolo 2022-10-11 582

Epoxy UV photocurable resin is widely used in electrical insulation casting, anti-corrosion coatings, metal bonding and other fields due to its high bonding strength, wide bonding surface, low shrinkage, good stability, excellent electrical insulation, high mechanical strength, good workability and other advantages. In recent years, epoxy UV photocurable resin as an industry has been booming.

However, the weather resistance of most epoxy products is relatively weak, especially in the production of epoxy adhesives, LED potting adhesives, epoxy UV light-curing resin accessories adhesives, etc., the product color requirements are strict, which also puts forward higher requirements for the anti-yellowing performance of epoxy system.

There are many factors that cause the epoxy products to yellow easily: 1. The structure of the aromatic epoxy UV photocurable resin bisphenol A is easy to oxidize and produce carbonyl group to form the yellow group; 2. 2. The free amine component in the amine curing agent is directly polymerized with the epoxy UV photocuring resin, resulting in local temperature rise and accelerated yellowing; 3. Tertiary amine promoters and nonylphenol promoters are easy to change color under hot oxygen and UV irradiation; 4, the reaction process temperature is too high, the residual impurities in the system, metal catalyst will induce yellowing.

The effective solution is to add antioxidants and UV absorbers, which can effectively prevent and delay yellowing. However, there are many kinds of antioxidants, and the selection of suitable products requires certain technical support and experience accumulation.

The classification of antioxidants, one is the main antioxidant: capture peroxide free radicals, mainly blocked phenolic antioxidants; One is auxiliary antioxidant: decomposition of hydroperoxides, mainly phosphite esters, thioesters. In general, according to the production process of each manufacturer and raw materials, solvents, additives, fillers, which stage of yellowing, yellowing degree of different, and it is recommended to use different antioxidants.

Ultraviolet light is the main culprit causing the oxidation and yellowing of the epoxy system, which is mainly from sunlight. Therefore, especially in the face of the production of products need to be used outdoors customers, we will recommend to add a certain amount of UV absorbent in the product, can effectively absorb UV, delay yellowing. In addition, ultraviolet light and antioxidants used together, can play a synergistic effect, play one plus one is greater than two effect.

Of course, the use of antioxidant and ultraviolet absorbent can not fundamentally solve the yellowing problem, but in a certain range and a certain time, or can effectively prevent the product oxidation yellowing, keep the product water color transparent, improve the grade of products.

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