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Modification additives improve the weather resistance of engineering plastics

2022-12-23

Antioxidant

The auxiliary agent whose main function is to inhibit thermal oxidation degradation of polymer resin belongs to the category of antioxidant. Antioxidants are the main type of plastic stabilization additives and almost all polymer resins involve the use of antioxidants. According to the mechanism of action, the traditional antioxidant system generally includes primary antioxidants, auxiliary antioxidants and heavy metal ion deactivators. The main function of the primary antioxidant is to trap polymer peroxyl radicals, and it is also known as peroxyl radical scavenger and chain terminating antioxidant. It involves two main types of aromatic amine compounds and hindered phenolic compounds. range of products. Auxiliary antioxidants have the function of breaking down polymeric peroxygen compounds, also known as peroxide degraders, including thiodicarboxylates and phosphite compounds, and are usually usedUsed in conjunction with primary antioxidants. Heavy metal ion deactivators are commonly known as anti-copper agents, which can complex transition metal ions and prevent them from catalyzing the oxidative degradation of polymer resins. Typical structures are hydrazide compounds, etc.

With the in-depth study of the theory of polymer antioxidants, the classification of antioxidants has also undergone some changes. Its outstanding feature is the introduction of the concept of carbon free radical scavenger. This kind of free radical scavenger differs from the main antioxidant in the traditional sense. They can scavenge polymer alkyl free radicals, which is equivalent to adding a line of defense to the traditional antioxidant system. Such stabilizing additives reported today mainly include aryl benzofuranone compounds, bisphenol monoacrylate compounds, hindered amine compounds and hydroxylamine vebonds. The ternary anti-oxidation system composed of additives can greatly improve the anti-oxidation stabilization ion effect of plastic products. It should be pointed out that amine antioxidants

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have coloring and contamination and are mostly used in rubber products, while Phenols Antioxidants and their composite antioxidant systems with supporting antioxidants and carbon free radical scavengers are mainly used in plastics and colorful rubber products.

Heat Stabilizer

If not specified, heat stabilizer refers to the stabilizer used in the processing of polyvinyl chloride and vinyl chloride copolymer. Polyvinyl chloride and vinyl chloride copolymers are heat-sensitive resins, which readily release hydrogen chloride during thermal processing, which in turn causes degradation reactions due to thermal aging. Heat stabilizerears generally achieve the purpose of heat stabilization by absorbing hydrogen chloride, replacing active chlorine and adding double bonds.

The types of heat stabilizers widely used in industry generally include main stabilizers such as basic lead salts, metal soaps, organic tin, organic antimony, epoxy compounds, phosphite, polyols, diketones and other auxiliary organic stabilizers. Compound stabilizers, consisting of main stabilizers, auxiliary stabilizers and other additives, play a vital role in the heat stabilizer market.

Light Stabilizer

Light stabilizer, also known as ultraviolet stabilizer, is a class used to inhibit the photo-oxidative degradation of polymer resins and improve the weather resistance of plastic products. Stabilizing additives. Photo stabilizers can be classified according to different stabilization mechanismseld in light shielding agents, ultraviolet absorbers, excited state quenchers and free radical scavengers.

Light shielding agents are usually carbon black, zinc oxide and some inorganic pigments or fillers, and their function is realized by shielding ultraviolet rays. Ultraviolet absorbers have a strong absorbing effect on ultraviolet rays, converting harmful light energy into harmless heat energy through intramolecular energy transfer, preventing polymer resins from absorbing ultraviolet energy and causing photo-oxidation reactions. There are many kinds of compounds involved in ultraviolet absorbers, mainly including benzophenone compounds, benzotriazole compounds, salicylate compounds, substituted acrylonitrile compounds and triazine compounds. The quencher in the excited state is intended to quench the energy on the excited polymer molecule so that it returns toreturns to the ground state, preventing further breakage of the polymer chain. Excited state quenchers are usually nickel complexes. The free radical scavenger uses hindered amine as the functional group, and the corresponding nitroxide radical is the basis for polymer free radical scavenging, and because this nitroxide radical is regenerated during the stabilization process, the light stabilization effect is very prominent. So far, it has developed into the light stabilizer category with the most varieties and the largest production and consumption. Of course, the effect of hindered amine light stabilizers is not limited to scavenging free radicals. Studies have shown that hindered amine light stabilizers often have the functions of simultaneously decomposing hydroperoxides and quenching singlet oxygen.

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