Antioxidants are a class of chemical substances, commonly known as "anti-aging agents". Add a small amount of antioxidants to the polymer. The amount of antioxidants added is generally only 0.1-0.5 parts, which can delay or inhibit the oxidation process of the polymer. , thereby preventing the aging of the polymer and extending its service life. For engineering plastics processing, antioxidants can prevent thermal oxidative degradation during processing of certain polymers (such as abs), allowing the molding process to proceed smoothly.
Ideal antioxidants
The ideal antioxidant should have the following conditions: 1 should have high antioxidant capacity: 2 good compatibility with the resin, no precipitation; 3 good processing performance. non-volatile at the processing temperature of the polymer, does not decompose; 4 Good resistance to extraction, insoluble in water and oil; 5 itself is preferably colorless or light color. It does not pollute the product; 6 is non-toxic or low-toxic; 7 is inexpensive.
In fact, any kind of antioxidant can not fully meet these conditions. Therefore, in actual use, according to the type, use and processing method of engineering plastics, the length of various additives is used together to produce synergistic effects.
With the development of engineering plastics industry, the use of antioxidants is increasingly widespread, and the demand is increasing. At present, engineering plastics widely used in antioxidants are polyamide, polyoxymethylene, aBS modified materials, etc.
Mechanism of action of antioxidants
According to the thermal oxidation mechanism of polymers, unstable radicals and hydroperoxides generated during thermal oxidation are the main factors causing deterioration of material properties. The mechanism of action of antioxidants is to terminate active radicals and decompose hydrogen. A free radical inhibitor with a free radical chain reaction is called a primary antioxidant. It contains two major series of amines and phenols. It is mainly used as a phenolic antioxidant in engineering plastics. It has decomposition. The hydroperoxide decomposition agent of hydroperoxidation is called a secondary antioxidant, and mainly includes two major classes of thioester and phosphite, and is usually used in combination with a primary antioxidant.
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