Antioxidants refer to those organic compounds that can inhibit or delay the thermal oxidation of polymers and other organic compounds in the air. Generally speaking, they are substances that can prevent polymer materials from being damaged due to oxidation. It is mainly divided into two categories, main antioxidant and auxiliary antioxidant. This paper mainly introduces several kinds of main antioxidants.

The main antioxidant mainly acts as a free radical cleaner. It generally prevents the damage of free radicals in the polymer by coupling reaction (i.e. termination of the reaction) or providing a hydrogen atom. The most common main antioxidants are phenolic antioxidants, amine antioxidants and amine/phenol synergistic antioxidants. Among them, the biggest advantage of phenolic antioxidants is that they have little impact on the color of products and will not pollute plastic products. Therefore, they are widely used in plastic products. Their toxicity is generally low, and they can be used for packaging or container products in contact with food.

(1) Hindered phenolic antioxidants: phenolic antioxidants have the structure of hindered phenols. It mainly includes alkyl monophenols, alkylated polyphenols, thiobisphenols, etc. In addition, there are derivatives of polyphenols and aminophenols. Alkylated phenol, containing a hindered phenol unit, has excellent non discoloration and non pollution. However, its molecular weight is generally small, its volatility and extractability are relatively large, and its anti-aging ability is greatly reduced.

Antioxidant 1076, as a new alkylated monophenol, introduces the ester group of long-chain alkyl into its structure, thereby increasing the molecular weight, reducing the volatility and improving the anti-aging ability. Generally, the alkyl groups in alkylated monophenols mainly include tertiary alkyl group and secondary alkyl group.

Antioxidant 264 (2,6-di-tert-butyl-4-methylphenol) is a widely used product, mainly used in natural rubber and synthetic rubber products, with the dosage of 0.5~2% generally. It has the function of resisting thermal oxygen aging. It can also be used as a stabilizer for polyethylene and polyvinyl chloride to inhibit the discoloration and strength decline of polystyrene and ABS resin, and the usage is less than 1%.

Antioxidant 2246 is an antioxidant with bisphenol structure, which has the advantages of low volatility and better effect. It is widely used in thermoplastics. Antioxidant 1010, chemically named IV[ β- (3,5-di-tert-butyl-4-hydroxyphenyl] pentaerythritol ester is one of the most widely used antioxidants. It has low volatility, heat resistance, water resistance and solvent extraction resistance, and has good compatibility with most polymers. It does not change color, pollution, and odor, and is suitable for high-temperature products. It is one of the best antioxidants for polyolefin plastics, with the dosage of 0.1-0.5% generally. It is mainly used for PVC, polyformaldehyde, polyamide, polyester, ABS, and butyl benzene, isoprene E, cis-1,4-polybutadiene and natural rubber.

(2) Amine antioxidants: The antioxidant effect is better than that of phenolic antioxidants. The biggest disadvantage is that it has discoloration and pollution, which will make the polymer discolor. It is mostly used in dark or black rubber and plastic products. The amine antioxidants commonly used in industry are octyl diphenylamine; 4.4 '- II（ α,α- Dimethylbenzyl) diphenylamine; N-phenyl-N '- isopropyl phenylenediamine; Hydrogenated quinoline mixture; N. N '- bis (1,4-dimethylamyl) - p-phenylenediamine; N-phenyl-N '- (p-toluenesulfonyl) - p-phenylenediamine, etc.

(3) Amine/phenol synergism: The above amine and phenol antioxidants focus on some important free radical chain termination reactions and the application of these compounds. When the above two types of antioxidants are used together, a synergistic effect can be observed.