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Application of Antioxidants

Antioxidants can delay or prevent the oxidation or self-oxidation process of polymers. They are called antioxidants. Antioxidants are a class of chemical substances. When there is only a small amount in the polymer system, they can delay or inhibit the oxidation process of polymers. Antioxidants can delay the deterioration of materials, products and supplies during storage and use, so it is also called "anti-aging agent". Generally, the dosage is small, and most of them are reductive substances. The general requirements for antioxidants are small dosage, high efficiency, low price, and no adverse consequences.


The mechanism of action of Antioxidants:


1. Stability of polymer using pre-antioxidant

Preventive or auxiliary antioxidants can decompose hydroperoxides without forming free radical intermediates. Therefore, they can prevent the branching of the chain caused by the decomposition of hydroperoxides into free radicals.


2. Synergy between antioxidants

A very famous example is bis-cinnamoyl thiodipropionate (DLTDP) or bisstearoyl thiodipropionate (DSTDP) and sterically hindered phenols, which are thermally stable in some polymers Sexual applications. Another very important example of synergy is the compounding effect of sterically hindered phenols and phosphite when improving the melt stability of polyolefins.


3. The stability of polymers using broken chain antioxidants

Antioxidants intervene in the reaction mechanism of chain reaction activity, namely, segment chain donor mechanism (CB-D) and segment chain receptor mechanism (CB-A).

The typical CB-D mechanism is the reaction between peroxide radicals and inhibitors such as phenols, followed by aromatic amines. The free radicals generated from the inhibitor AH can destroy a peroxide group PO2 as in the reaction formula (1-43).

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