Polymer and its related products such as plastics, rubber and synthetic fiber, during the process of usage and storage, due to the environmental impact, under the combined effects of heat, oxygen, water, chemical medium, light, and microorganisms, will undergo series changes in their chemical composition and structure. There will be also corresponding deterioration in the physical properties of becoming sticky, hard, brittle, and stiff, being cracked, or having color as well as losing intensity. All these changes are collectively called aging. Antioxidant refers to substance that can delay the aging process of polymer compound with most of these substances being able to inhibit oxidation, and some can inhibit the action of heat and light, thereby extending the life of the product.
There are various kinds of reasons that can lead to the aging of the polymer with various kinds of corresponding Antioxidants. General antioxidants, anti-ozone agents, radical inhibitors, inhibitors of harmful metals, UV stabilizers, preservatives, stabilizers, light stabilizers, retarders and a polymerization inhibitor can all be used as an antioxidant. Moreover, for different polymers, in different environmental conditions, the choice of antioxidant also varies. According to their chemical properties, it can be divided into the following five categories.
1. Ketone amine condensate: this kind of condensate is effective in preventing the aging caused air and ozone. For example, the cryogenic condensate of acetone and diphenylamine has good anti-aging effect on the polymer. The condensate of acetone and phenylacetate naphthylamine appears as a light brown, non-toxic powder, being able to be dissolved in acetone and dichloroethane. It is applicable to natural rubber adhesives, neoprene adhesives and nitrile adhesives.
2. Aldehyde amine condensate: condensate of aldehyde amine has moderate efficacy on the aging caused by air. It is applicable to natural rubber adhesives and synthetic rubber adhesive. With the increased usage amount, it can improve the heat resistance of the adhesive. For example, the condensate of aldehydes and naphthylamine is a non-toxic orange or dark red resinous solid.
3. The aromatic amine: the aromatic amine a kind of Antioxidants of specific efficacy with different Antioxidants having different special effects. For diene type of adhesive (natural rubber or some synthetic rubber adhesive), people mostly use phenyl-2-naphthylamine and phenyl -β-naphthylamine. Another example is the meta-toluenediamine which has moderate efficacy against aging caused by air and heating. However, it has relative high anti-aging performance in the uncured rubber adhesive.
4. Aromatic diamine: diphenylamine derivative is an excellent kind of air Antioxidant with its performance being related to the nature of the substituents.
5. Quinoline derivative: quinoline derivative is effective in anti-air, anti-ozone aging. Antiozonants are mostly the p-phenylenediamine derivatives.