Anti-aging agent is one of the important rubber auxiliary materials in rubber products, the reasonable addition of antioxidant can significantly extend the service life of rubber products. In actual production, according to the different performance requirements, some recycled rubber products can add an antioxidant, some need to add more than two kinds of antioxidants. This is mainly because multiple varieties of antioxidants used in recycled rubber products will produce three major effects: counteracting effect, additive effect and synergistic effect.

1. rubber antioxidant in the recycled rubber products and the effect of the sum
Practical example: When two phenolic antioxidants with different volatility are selected in the recycled rubber products, the antioxidants in the recycled rubber can not only produce a summation effect, but also can play an inhibiting effect in a wider range of temperature compared with the equivalent amount of one antioxidant alone.

The summation effect of rubber antioxidant is that the protection effect produced by the antioxidant is equal to the sum of the effect of each used separately, and the summation effect is the basic requirement for choosing antioxidant for recycled rubber products.

2. The confrontation effect of rubber antioxidant in recycled rubber products
Actual case: natural rubber / latex recycled rubber and the production of rubber products, the use of 4010NA as an antioxidant, the addition of polysulfide oxidation rate increased, that is, the effect of confrontation. Carbon black is the most commonly used reinforcing agent in recycled rubber products, which can inhibit oxidation as well as help oxidation in recycled rubber; in the presence of chain-breaking antioxidant, the inhibiting effect of carbon black is reduced, and the protective effect of antioxidant decreases in the presence of carbon black, which is also the counter effect.

3. The synergistic effect of rubber antioxidant in recycled rubber products
Practical examples: Antioxidant D and antioxidant WSP can have synergistic effect with antioxidant MB; Antioxidant 2246 and antioxidant 4010 can have synergistic effect with antioxidant DLTDP in DCP vulcanized natural rubber/latex recycled rubber.

The synergistic effect of rubber antioxidants means that the protective effect of antioxidants used together is greater than the sum of the effect of each antioxidant used separately. In practice, the synergistic effect of antioxidants can be divided into uneven synergistic effect (synergistic effect of two or more antioxidants acting by different mechanisms) and uniform synergistic effect (synergistic effect of two or more antioxidants acting by the same mechanism).