【Deep Coating Society Coating Technology】What is the mechanism of action of antioxidants?

Antioxidants are not antioxidants, the two are very different, antioxidants are a class of chemicals, when they are only a small amount in the polymer system, will delay or inhibit the oxidation process of the polymer, thereby preventing the aging of the polymer and prolonging its service life, for engineering plastic processing, antioxidants can prevent the thermal oxidation degradation of some polymers during processing, so that the molding process can be carried out
smoothly.
The amount of antioxidant added - usually only 0.
1-0.
5
.

Ideal antioxidant required conditions

The ideal antioxidant should have the following conditions: high antioxidant capacity: good compatibility with the resin, no precipitation; Good
processability.
It does not volatilize or break down
at the processing temperature of the polymer.
Good resistance to extraction, insoluble in water and oil; The color itself should be colorless or light
.
Avoid contaminating the product; Non-toxic or low-toxic; Non-toxic at a low
price.

In fact, any kind of antioxidant can not fully meet these conditions, therefore, in actual use, often according to the type of engineering plastic, use and processing method, the length of various additives, used together, in order to produce synergistic effects
.

With the development of the engineering plastics industry, the use of antioxidants is becoming more and more extensive, the demand is increasing, at present, the antioxidants widely used in engineering plastics are polyamide, formaldehyde, ABS and so on
.

According to the thermal oxidation mechanism of the polymer, the unstable free radicals and hydroperoxides produced during the thermal oxidation process are the main factors leading to the decline of material properties, and the mechanism of action of the antioxidant is used to terminate the active radicals
and decompose
the hydroperoxide.

Free radical inhibitors with antioxidants that inhibit differences in free radical reactions are known as primary antioxidants, and they contain a range of amines and phenols, and the phenols used in engineering plastics are mainly antioxidants
.

Hydroperoxide decomposers with the function of destroying the structure of hydrogen peroxide are called auxiliary antioxidants, mainly including thioesters and phosphite esters, and are often used
in conjunction with major antioxidants.

END

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