Vulcanization accelerator refers to the substance that can shorten the vulcanization time and reduce the vulcanization temperature after adding the rubber compound, which can effectively improve the rubber vulcanization efficiency and improve the physical properties of the vulcanized rubber. For example, when using 3 parts sulfur vulcanization of 100 parts of natural rubber, the optimal vulcanization time is about 5 hours, and with 5 parts of zinc oxide, 1 part of the accelerator M and 1 part of stearic acid, the time to complete the vulcanization is only 20-30 minutes.
1. Classification of rubber accelerators
Rubber vulcanization accelerators are classified according to their chemical structure, which can be divided into thiazoles, sulfonamides, thiurames, dithiocarbamates, guanidines, thioureas, xanthates and aldehydes. According to the acidity and alkalinity of the rubber accelerator itself or the acidity and alkalinity generated by the reaction with hydrogen sulfide, it can be divided into acid accelerator, alkaline accelerator and neutral accelerator.
Acid accelerators: they are acidic or react with hydrogen sulfide to form acidic compounds, and thiazoles, thiurames, dithiocarbamates, xanthates, etc. are acid accelerators.
Alkaline accelerators: they are alkaline or react with hydrogen sulfide to form alkaline compounds, such as guanidine accelerators and aldehyde amine accelerators. Neutral accelerator: reacts with hydrogen sulfide to form acidic and basic compounds at the same time or salts that can dissociate into basic and acidic compounds, such as hyposulfonamides and thiourea accelerators.
2. Performance characteristics of rubber accelerators
The ideal rubber accelerator should have the following four functions: (1) long scorch time (high processing safety before vulcanization); (2) Short vulcanization time (fast start of vulcanization and high production efficiency); (3) The vulcanization curve is flat (the flat vulcanization time is long, and there is no vulcanization return); (4) Non-toxic and non-polluting. In actual production, the accelerator is added to the rubber together with other vulcanization system additives, and no scorching can occur in the process of mixing, extrusion and other processes before vulcanization, and cross-linking is completed in a short time as far as possible during the vulcanization process.
Sulfonamide accelerators have a long scorching time, fast vulcanization start, flatness, and are widely used in the production of rubber products. The scorching time of thiuram accelerator is very short, and vulcanization can be completed in a short time. The vulcanization curve of guanidine accelerator is gently sloped. The vulcanization curve of thiazole rubber accelerator has a certain flatness.
3. Rubber vulcanization accelerator selection skills
When producing rubber products with high unsaturated rubber such as natural rubber, styrene-butadiene rubber, and isoprene rubber as the main raw materials, hyposulfonamide accelerators are generally used, and guanidine and thiazole accelerators are used. When producing rubber products with low unsaturated rubber such as butyl rubber and EPDM rubber E4LYY524 as the main raw materials, the sulfur vulcanization system of thiuram or dithiocarbamate, or p-quinone oxime, or resin vulcanization system is mostly used. When producing products containing halogenated rubber such as neoprene, thiourea accelerators can be used.
Rubber on the market can be divided into three categories, natural rubber, synthetic rubber and recycled rubber, rubber vulcanization accelerator plays a vital role in rubber processing, reasonable selection of rubber accelerator can significantly improve the production efficiency and quality of rubber products. With the continuous development of the rubber industry, the performance requirements for vulcanization accelerators are also increasing to meet the market demand for high-performance rubber products.
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