Plastic antioxidants are sensitive to oxidative degradation for most plastics in the manufacturing, processing, storage, and application processes. Oxygen penetrates plastic films and reacts with most polymers. Causes degradation or cross-linking, which changes the properties of the material.
The oxidation process of the polymer is a free-radical chain reaction. Plastic antioxidants are substances that trap active free radicals, generate non-reactive free radicals, or decompose polymer hydroperoxides that are generated during oxidation, stop chain reactions, and delay polymer oxidation. . So that the polymer can be processed smoothly, and extend the service life.
Plastic antioxidants have been widely used in plastics, among which polyolefins and ABS are most used, followed by polyoxymethylene, polyvinyl chloride and nylon. In the use of more than two types of antioxidants should be fully used, can produce additive or synergistic advantages, in order to obtain better benefits.
1 Additive Benefits: When primary antioxidants and auxiliary antioxidants are used together, they have their own characteristics and are better than using one alone. The use of a high concentration of antioxidants can cause side reactions, and when several low concentrations of antioxidants are used, side reactions can be avoided and additive effects can be achieved.
The chemical structure of plastic antioxidants can be divided into:
(1) Phenols, including: monophenols, bisphenols, triphenols, polyphenols, hydroquinone, thiobisphenols;
(2) Amines, including: naphthylamine, diphenylamine, p-phenylenediamine, quinoline derivatives, as well as phosphites, thioesters, and others.
2 Synergy: When the antioxidants are used properly, their total efficacy exceeds the sum of their respective efficacies used alone, and they are considered synergistic.
Finally, different plastics have different oxygen stability, so some plastics do not require antioxidants. Others must add antioxidants. The role of plastic antioxidants is to trap active free radicals and disrupt the chain reaction in order to delay the oxidation process and speed of plastics. According to the mechanism of action of the antioxidant, it is effective for all plastics.
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