The principle of Diphenylamine as a rubber antioxidant

Diphenylamine as a rubber antioxidant mainly works through the following principles:

1. Antioxidant effect

During the use and storage of rubber, it will react with oxygen in the air to form free radicals, which will then cause the breakage and cross-linking of the rubber molecular chain, causing the performance of the rubber to deteriorate. There is a pair of lone pairs of electrons on the nitrogen atom in Diphenylamine, which has a strong electron-donating ability and can react with the free radicals generated during the oxidation of rubber to provide hydrogen atoms, thereby converting the free radicals into relatively stable compounds, terminating the free radical chain reaction, slowing down the oxidation rate of rubber, and playing an antioxidant role.

Diphenylamine itself can be oxidized to quinone compounds with stable structures under certain conditions. These quinone compounds can further react with free radicals or other active substances in rubber, thereby consuming harmful free radicals in rubber and inhibiting the oxidation and aging of rubber.

2. Anti-ozone effect

Ozone can react with double bonds in rubber, resulting in the breakage of rubber molecular chains and surface cracking. Diphenylamine can form a protective film on the rubber surface to prevent direct contact between ozone and rubber molecules, thereby slowing down the erosion of ozone on rubber.

Diphenylamine can react with free radicals produced by ozone decomposition in rubber, capture them and convert them into stable products, prevent free radicals from further triggering rubber aging reactions, and reduce the destructive effect of ozone on rubber.

3. Anti-fatigue effect

Rubber is prone to fatigue aging under dynamic stress such as repeated stretching, compression and bending. Diphenylamine can increase the cross-linking density of rubber, enhance the interaction between rubber molecular chains, and reduce the relative sliding and deformation of molecular chains when rubber is subjected to external forces, thereby improving the anti-fatigue performance of rubber.

Diphenylamine can reduce the heat generation of rubber under dynamic stress, reduce the accelerated aging of rubber caused by heat accumulation, and extend the service life of rubber.

4. Metal ion passivation effect

During use, rubber products may come into contact with some metal ions, such as copper, iron, manganese, etc. These metal ions will catalyze the oxidation reaction of rubber and accelerate the aging of rubber. Diphenylamine can react with these metal ions to form a stable complex, thereby reducing the catalytic activity of metal ions and reducing their promotion of rubber aging.