In the vulcanization of rubber, where can accelerate the rubber and vulcanization agent reaction rate of the material, collectively referred to as vulcanization accelerator.Promoter plays a very important role in rubber vulcanization, add a small amount of promoter, can greatly accelerate the reaction between rubber and vulcanizing agent, improve the curing speed, shorten the curing temperature, curing time, reduce the dosage of curing agent, improve physical and mechanical properties of vulcanized rubber, such as improve the tensile strength, tensile modulus, hardness and abrasion resistance, improve the aging resistance of vulcanized rubber, can prevent spray frost, enlarge the using range of vulcanized rubber, can be made transparent and various colors of rubber products.Therefore, the promoter has been one of the essential raw materials in the rubber industry.
Accelerants can be divided into inorganic and organic materials.Inorganic accelerator since the discovery of more than a hundred years, but because of its low efficiency, vulcanized rubber performance is poor, in addition to a small amount of use in a few cases, the current has been replaced by organic accelerator, inorganic accelerator zinc oxide, magnesium oxide, calcium oxide, alkali carbonate and so on are now mostly used as organic accelerator active agent.
Due to the high efficiency of organic accelerator, good vulcanization characteristics, vulcanized rubber physical and mechanical properties and aging properties, so that this kind of accelerator has been developed rapidly.At present, there are more than 100 kinds of commodities, but only 50 or 60 kinds are commonly used.
According to the chemical structure, it can be divided into: dithiocarbamate, xanthate, thiolane, thiazole, sulfonamide, aldose amine, guanidine, thiourea, amine and so on.According to the degree of promoting effect, the promoters can be divided into: super promoters, medium super promoters, medium speed promoters and weak promoters.
Because of the different types of rubber, the same accelerator can not promote the vulcanization of different rubber.For natural rubber and most general synthetic rubber (such as butyl benzene rubber, butyl butyl rubber, isopentyl rubber), generally belong to the superaccelerator dithiophenyl formate, xanthate and thiuram type accelerator;Belong to the Chinese super accelerator thiazole, sulfonamides and part of the aldose amine accelerator;Medium speed accelerators include thiourea, guanidine and some aldose amine accelerators;The weak promoters are amines and some aldehydes and amines.
Also according to the accelerator and hydrogen sulfide reaction of the acid, alkaline or neutral, and the accelerator is divided into acid accelerator, alkaline accelerator and neutral accelerator.
The following factors should be considered when selecting promoters to choose the appropriate type of promoters for different rubber materials.
Different types of rubber rubber with different vulcanization system, including the type of accelerator selection and matching.
(3) coke burning performance promoter on the coke burning time of the material plays a decisive role, so the choice must ensure that the material in ordinary processing (mixing, rolling, pressing) will not prematurely vulcanized.
(4) vulcanized rubber resistance to return to the original this is particularly important in the original products, because of the poor thermal conductivity of rubber, the hot parts should choose better resistance to return to the original rubber accelerator, so as to avoid the rubber in the process of vulcanization reduction phenomenon.
(5) vulcanized rubber performance selection accelerator, in addition to ensure the processing of the rubber, but also to pay attention to meet the requirements of product performance, can be adjusted by the vulcanized system to improve the physical and mechanical properties of vulcanized rubber and aging resistance.
In addition to the above factors, should also take into account the rubber vulcanization accelerator in the rubber dispersion, pollution, coloration, toxicity and other coordination agents.