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    Home > Chemicals Industry > New Chemical Materials > Epoxy resin is easy to turn yellow!

    Epoxy resin is easy to turn yellow!

    • Last Update: 2022-03-20
    • Source: Internet
    • Author: User
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    Due to the advantages of high bonding strength, wide bonding surface, low shrinkage, good stability, excellent electrical insulation, high mechanical strength, and good processability, epoxy resin is widely used in electrical insulation casting, anti-corrosion coatings, Metal bonding and other fields
    .
    In recent years, epoxy resin has flourished as an industry

    .
    ? But the weather resistance of most epoxy products is relatively weak, especially when producing epoxy adhesives, LED potting adhesives, epoxy resin ornaments, etc.
    , the product color requirements are strict, and the epoxy system is also resistant to yellowing Performance puts forward higher requirements

    .
    ? There are many factors that cause epoxy products to turn yellow:? 1.
    The structure of aromatic epoxy resin bisphenol A is easy to oxidize to produce carbonyl groups to form yellowing groups; 2.
    The free amine component of the amine curing agent directly interacts with the epoxy resin Polymerization leads to a local temperature increase and accelerates yellowing; 3.
    Tertiary amine accelerators and nonylphenol accelerators are easy to change color under hot oxygen and UV irradiation; 4.
    The temperature is too high during the reaction, and the remaining impurities in the system , Metal catalysts can induce yellowing

    .
    ? The effective solution is:? Adding antioxidants and ultraviolet absorbers can effectively prevent and delay yellowing

    .
    However, there are many types of antioxidants, and selecting suitable products from them requires certain technical support and experience accumulation

    .
    ? Classification of antioxidants? One is the main antioxidant: capturing peroxide free radicals, mainly hindered phenol antioxidants;? One is the auxiliary antioxidant: decomposing hydroperoxides, mainly phosphites , Thioesters

    .
    Under normal circumstances, it is recommended to use different antioxidants according to the production process and raw materials, solvents, auxiliaries, and fillers of various manufacturers, which stage of yellowing and the degree of yellowing are different

    .
    ? The important culprit that causes the oxidative yellowing of epoxy systems is also ultraviolet rays, which are mainly from sunlight.
    Therefore, especially for customers who need to use the products outdoors, we will recommend adding a certain amount of ultraviolet rays to the products.
    Absorbent, can effectively absorb ultraviolet rays and delay yellowing

    .
    Moreover, the use of ultraviolet rays and antioxidants together can have a synergistic effect, with the effect of 1 plus 1 being greater than 2.

    .
    ? Of course, the use of antioxidants and ultraviolet absorbers cannot fundamentally solve the yellowing problem, but within a certain range and within a certain period of time, it can still effectively prevent the product from oxidizing yellowing, keep the product water color transparent, and improve the product.
    The grade

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