There are three types of chemicals that can be used as rubber anti-scorching agents, namely organic acids, nitroso compounds and sulfonamides.
(1) Organic acids Such as salicylic acid, benzoic acid, o-acetic benzoic acid, phthalic anhydride. This type of chemical has weak anti-scorching ability and is highly selective in accelerator types. It will reduce the vulcanization rate and vulcanized rubber performance and irritate the skin. Among them, phthalic anhydride is more commonly used, which can be used for light-colored rubber products. It is only effective for alkaline accelerators DPG and MBT accelerators, and is ineffective for NOBS and TMTD.
(2) Nitroso compounds N-nitrosodiphenylamine, N-nitroso-phenyl-β-naphthylamine, N-nitroso-2,2,4-trimethyl-1,2-dihydroquinoline polymer. Among them, N-nitrosodiphenylamine (NDPA) is commonly used. Unlike organic acids, this type of anti-scorching agent has a good anti-scorching effect on commonly used thiazole and sulfonamide accelerators.
(3) Sulfonamide anti-scorch agents are a series of compounds containing S-N bonds, and the general molecular structure formula is as follows:
Different R groups can produce anti-scorch agents with different properties. Among them, commercial CTP or PVI are excellent anti-scorch agents.
Any anti-scorch agent should meet the requirements of rubber processing performance, that is, it has excellent anti-scorch performance; low selectivity for different accelerators and scorch types; insensitive to other compounding agents; no adverse effects on the vulcanization characteristics of the rubber and the performance of the vulcanized rubber; storage stability and good operating performance; no caking, no flying, easy to disperse, no frosting; and meet the requirements of process safety and hygiene.
