Chemicals formulated into rubber to delay the aging of rubber products are called antioxidants. During use, rubber products are subjected to the effects of heat, oxygen, light, metal ions, dynamic fatigue, etc., and the physical properties are reduced or the surface is cracked, and their functions cannot be maintained. In order to maintain the function of rubber products for a long time, it is very important to add antioxidants.
Select the appropriate antioxidant according to the type of raw rubber used in rubber products and processing conditions. For example, for diene rubbers containing double bonds in rubbers such as NR and SBR, ozone cracking occurs on the surface of the rubber, so an anti-ozone cracking agent is required.
As the criteria for selecting antioxidants, the anti-oxidation effect, the anti-ozone cracking effect, the anti-flexing cracking effect, the effect on blooming, coloring (pollution), vulcanization, and the durability of the anti-aging effect (difficult to use) can generally be considered. Volatile, difficult to extract), hygiene, etc. The general dosage is 0.5 to 3 parts, and 5 parts are sometimes added when the responsibility is considered to be sustainable.
Among the antioxidants for rubber, aromatic amine antioxidants are the most used. However, such antioxidants cannot be used in white or bright-colored rubber products because of their coloring properties, that is, contamination. In this case, a slightly less effective phenolic antioxidant can be used.
In addition, a radical chain inhibition type antioxidant such as an aromatic amine or phenol type antioxidant is used in combination with a peroxide decomposition type benzimidazole type antioxidant. Due to the synergistic effect, the antioxidant effect can be further improved.
N-isopropyl-N´-phenyl-p-phenylenediamine and N-phenyl-N´-(1,3-dimethylbutyl)-p-phenylenediamine and other p-phenylenediamine antioxidants are , anti-ozone, anti-flex cracking effect is good, so it is mostly used for diene rubber such as NR and SBR.
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