This article summarizes the selection and use of antioxidants in the most important six aspects to elaborate on how to cost-effective use of antioxidants, in order to achieve twice the result with half the effort, and effectively control the quality of some products that may arise. This is the antioxidant selection of the six control: control of anti-aging effect, control the precipitation rate, control the appearance of the product, control the surface frosting, control the cost of the formula, control the use of safety.

Control of anti-aging effect
The anti-aging effect here is the products exposed to what kind of environment, and how long after the use of the product can not happen after aging. This depends greatly on the reactivity and migration speed of the antioxidant.

1. Reactivity
Generally, the reactivity of aromatic amine antioxidants, especially p-phenylenediamine antioxidants, is higher than that of other types of antioxidants. This is because of the amine group in the N atom of the lone pair of electrons by the benzene ring conjugation, so that the N-H covalent bond electron cloud density increases, so connected to the N atom on the hydrogen atom is more active, more likely to be reacted with free radicals and the loss of active hydrogen in the anti-aging reaction. The active hydrogen of phenolic antioxidants is located in the phenolic hydroxyl group on the benzene ring in the opposite position, the reactivity of the C-H covalent bond is not as high as that of the aromatic amine antioxidants in the N-H covalent bond. Therefore, it can be used as a long-lasting antioxidant.

By the same token, if both antioxidants are p-phenylenediamine antioxidants, the substituent group R is alkyl when the N-H bond electron cloud density is higher than the substituent group R is an aromatic hydrocarbon group, so the former reactivity is higher than the latter. For example, the reactivity of 7PPD is higher than that of 6PPD, the static antioxidant effect of the former is better, while the comprehensive antioxidant effect of the latter is more outstanding.

When selecting antioxidants, the higher the reactivity, the better. It is necessary to consider several aspects such as performance requirements, use environment and cost.

2. Migration speed
The anti-aging effect of rubber is also related to the migration speed of the antioxidant. The surface of rubber is most prone to oxidative aging due to long-term exposure to oxygen. Moreover, as the surface rubber ages and cracks, oxygen gradually diffuses to the inside of the rubber and further aging occurs. Therefore, migration to the rubber surface of this part of the antioxidant to resist rubber aging plays an important role. The faster the migration speed of the antioxidant, the better its initial anti-aging effect.