What should we pay attention to when choosing antioxidants?

[Summary description] When selecting antioxidants, pay attention to the cooperation between antioxidants and the cooperation between antioxidants and other heat and light stabilizers. Next, consider the use of antioxidants. Most antioxidants have an optimal concentration range.

When selecting antioxidants, pay attention to the cooperation between antioxidants and the cooperation between antioxidants and other heat and light stabilizers. Next, consider the use of antioxidants. Most antioxidants have an optimal concentration range. Within this range, as the dosage of antioxidants increases, the antioxidant effect increases to the maximum value. Exceeding this range will have adverse effects. The dosage of antioxidants depends on many factors such as the properties of the plastic, the efficiency of the antioxidants, synergistic effects, application conditions and cost quotation of the product. Generally, amine antioxidants are more active than phenolic antioxidants, so they should have greater antioxidant effects. However, the former will change color under the influence of oxygen and light in the air, and they are often colored and toxic. Therefore, use caution when using plastics. Now the first priority is to consider the cooperation of antioxidants.
(l) Additive effect.
The combined use of multiple antioxidants can bring out their respective characteristics and effects, increasing the total effect. For example, when hindered phenols with different degrees of evaporation or steric hindrance are used together, their antioxidant effects can be exerted within a wide temperature range, and the effect is enhanced. If only one antioxidant is used in the formula, a large amount must be added, which will cause severe oxidation reactions at high concentrations, which is not allowed. However, when several low-concentration antioxidants are used together, it can not only achieve the required purpose, but also prevent severe oxidation and exert its additive effect.
(2) Synergy effect.
① When two main antioxidants with different activities are used together, the high-activity antioxidant donates hydrogen atoms to stop the active chain produced by oxidation; while the low-activity antioxidant can donate hydrogen atoms to the high-activity antioxidant. , it regenerates and exerts a long-lasting antioxidant effect, so the antioxidant effect is very good.
② When using primary and auxiliary antioxidants together, attention should be paid to promoting the synergistic effect. For example, the main antioxidant easily gives out hydrogen atoms, and the hydrogen atoms can convert the peroxide free radicals into hydroperoxides to initiate a chain reaction; then the hydroperoxides act as peroxide decomposers of the auxiliary antioxidants, Generates an inactive, stable product. Therefore, the oxidation reaction speed is greatly slowed down and the antioxidant effect is increased. For example, the system of antioxidant 264 and DLPT, which is widely used in polyolefins, is an example.
③An antioxidant molecule has two or more different stable functions, which is called self-synergistic effect. For example, sulfur-containing hindered phenolic antioxidants have chain reaction inhibitors and peroxide decomposers. With two layers of effects, this antioxidant can enhance the antioxidant effect and is an ideal antioxidant.