When selecting antioxidants, attention should be paid to the cooperation between antioxidants

When selecting antioxidants, attention should be paid to the cooperation between antioxidants

When selecting antioxidants, attention should be paid to the cooperation between antioxidants and other heat and light stabilizers. The specific content is as follows: (1) Sum up effect.

The combination of multiple antioxidants can enhance their respective characteristics and effects, thereby increasing the overall effect. For example, when hindered phenols with different degrees of evaporation or steric hindrance are combined, their antioxidant effects can be enhanced over a wide temperature range. If only one type of antioxidant is used in the formula, it will inevitably involve a large amount and cause intense oxidation reactions at high concentrations, which is not allowed. But when using several low concentration antioxidants together, it not only achieves the desired intention, but also prevents intense oxidation and promotes its additive effect.

(2) Synergy effect.

① When two main antioxidants with different activities are used together, the highly active antioxidant gives hydrogen atoms, causing the active chain involved in oxidation to stop; Low activity antioxidants can supply hydrogen atoms to high activity antioxidants, allowing them to regenerate and develop durable antioxidant effects, thus resulting in excellent antioxidant performance. ② When using a combination of rich and auxiliary antioxidants, attention should be paid to promoting synergistic effects. If the main antioxidant simply gives hydrogen atoms, hydrogen atoms can convert peroxide free radicals into hydrogen peroxides, stopping the chain reaction; Then the hydrogen peroxide reacts with the peroxide differentiation agent of the auxiliary antioxidant to generate a non active and stable product. Therefore, it greatly slows down the rate of oxidation reaction and adds antioxidant effect. ③ A molecule of an antioxidant has two or more different stabilizing functions, known as self synergistic effect. For example, sulfur-containing hindered phenolic antioxidants have a two-layer effect of chain reaction stopping agent and peroxide differentiation agent. This antioxidant can enhance the antioxidant effect and is a relatively negative antioxidant. ④ When antioxidants are used in combination with heat and light stabilizers, those with synergistic effects should be selected, while efforts should be made to prevent antagonistic effects. As with most amine and phenolic antioxidants, the aging effect can be significantly reduced in the presence of carbon black, which may be due to the fact that carbon black directly catalyzes the oxidation of antioxidants, consuming some of them. Antioxidants containing sulfur-containing ether bonds have a synergistic effect with carbon black, so the latter is chosen.