(1) Phenolic antioxidants
Phenolic antioxidants are the most widely used and most abundant antioxidants in polymer materials. The phenolic hydroxyl group in phenolic antioxidants can release active hydrogen to capture the ‘key offender’ free radicals in polymer degradation. Natural products such as VE, tea polyphenols, and low molecular compounds such as 2,6-di-tert-butylphenol (BHT) are phenolic antioxidants. Hindered phenolic antioxidants are a class of compounds with substituents on one or both sides of the hydroxyl group (-OH) on the benzene ring. Because the hydroxyl group is spatially hindered, the H atom is easily dislodged from the molecule with peroxyl radicals (ROO .) , alkoxyl radicals (RO.), hydroxyl radicals (.OH), etc. to combine to make them inactive, thus terminating the chain reaction of thermo-oxidative aging. Hindered phenolic antioxidants are non-polluting products and are suitable for colourless or light-coloured products. Moreover, hindered phenolic antioxidants have large molecular weight, good compatibility with polymer materials and low toxicity, so the consumption ratio of high molecular weight hindered phenolic varieties represented by 1010 and 1076 increases year by year, while 1010 becomes the most excellent product among polymer antioxidants with high molecular weight, good compatibility with polymer materials, excellent antioxidant effect, good safety, and the largest consumption.
(2) Phosphite antioxidants
Phosphite antioxidant main role is to remove hydroperoxides, not only polymer degradation will produce hydroperoxides, and the main antioxidant to inhibit the addition of hydroperoxides at the same time will also produce hydroperoxides. Therefore, as an auxiliary antioxidant, phosphite antioxidants are not very effective when used alone, but have a significant effect when used together with the main antioxidant. Phosphite antioxidant representative product 168 is the domestic production and consumption of antioxidant varieties second only to 1010. 626 and 618 are mainly used for high temperature processing of polymer materials or products around 300 ℃, the role of the polymer materials to effectively improve the resistance to high-temperature thermal oxidation, while maintaining the good appearance of polymer products.
(3) Sulfur antioxidants
Sulfur antioxidants and phosphorus antioxidants similar to the role of the main role is to remove hydroperoxides, but also as an auxiliary antioxidant. Domestic production of sulfur-containing antioxidants according to the molecular structure can be divided into sulfur ester antioxidants, sulfur bisphenol antioxidants and sulfur ether phenolic antioxidants 3 varieties. Thiobisphenol antioxidant molecule contains hindered phenol structure, in the polymer materials show high oxygen resistance, heat resistance, usually thiobisphenol antioxidant is divided into the main type of hindered phenol antioxidant.
(4) Metal ion passivator
Metal ion passivators contain hydrazide, oxime and aldehyde-amine condensate and other coordination groups, complexation of metal ions. The most representative product is 1024, which is a dihydrazide-type compound and also contains a combined hindered phenol functional group, which gives the product both copper resistance and resistance to heat and oxygen aging.
(5) Aromatic amine antioxidants
Aromatic amine antioxidants are generated by the condensation of aminophenol or hydroquinone with aniline, this type of product is darker in colour, is a polluting antioxidant, and most of the products have a certain degree of toxicity, a large number of rubber products, other polymer materials, the use of less, and this type of antioxidant is also known as antioxidant.
