Basic introduction of rubber curing oven
Rubber becomes soft when heated, becomes hard and brittle when cold, is not easy to be formed, is easy to wear, easily soluble in organic solvents such as gasoline, has double bonds in the molecule, easily causes addition reactions, and is easy to age. In 1839, Goodyear inadvertently produced vulcanized rubber.
In order to improve the performance of rubber products, a series of processing processes are performed on the raw rubber during production. Under certain conditions, the raw rubber in the rubber and the vulcanizing agent are chemically reacted to form a cross-linked macromolecule into The three-dimensional network structure of the macromolecules makes the rubber material with high strength, high elasticity, high wear resistance, corrosion resistance and other excellent properties. This process is called rubber vulcanization.
Vulcanization is the basic process for rubber compounds to form a three-dimensional network structure through the cross-linking of raw rubber molecules. Different curing systems are suitable for different raw rubbers. Rubber (raw rubber) as the main body, and a variety of auxiliary materials made of composite (several major systems of auxiliary materials, filling and reinforcement, vulcanization, protection, plasticization, special substance additives, etc.) A treatment method after the insulation layer or the sheath layer is to make the vulcanization system in the auxiliary system work to permanently crosslink the rubber, increase elasticity, and reduce plasticity. The term of vulcanization is called vulcanization because the earliest time was to crosslink rubber with sulfur, and it is still used today.
Generally, the vulcanization process is divided into four stages, induction-presulfurization-normal sulfurization-persulfurization. In order to achieve this reaction, energy must be added to reach a certain vulcanization temperature, and then the rubber is kept at the vulcanization temperature range to complete the entire vulcanization reaction.
As the raw rubber of vulcanized rubber, only rubber that can be crosslinked with sulfur or peroxide can be used.
Vulcanized rubber system
Unsaturated rubber
The following types of vulcanization systems are commonly used
(1) Sulfur, organic disulfides and polysulfides, thiazoles, diphenylguanidines, zinc oxide and stearic acid. This is the most versatile cure system. However, the heat-resistant oxygen aging performance of the vulcanizate obtained is not high.
(2) Alkyl phenolic resin.
(3) Polyhalides (such as hexachloroethane for polybutadiene rubber, styrene-butadiene rubber and nitrile rubber), hexachloro-p-xylene.
(4) Bifunctional reagents [such as quinones, diamines, azo and phenylazo derivatives (for butyl rubber and ethylene-propylene rubber), etc.
(5) Bismaleimide, diacrylate. Divalent metal acrylate (methacrylate), pre-polyether acrylate.
(6) Organic peroxides for vulcanized saturated rubber.
Saturated rubber
(1) When vulcanizing EPDM rubber, use organic peroxides and unsaturated cross-linking reagents, such as triallyl isocyanurate (TAIC).
(2) Organic peroxides can also be used when curing silicone rubber. Vinyl silicone rubber can be vulcanized with the participation of catalyst (Pt).
Rubber vulcanization process
According to the curing conditions, it can be divided into three types: cold curing, room temperature curing and hot curing.
Cold vulcanization
Cold vulcanization can be used for the vulcanization of thin film products. The products can be dipped in a carbon disulfide solution containing 2% to 5% sulfur chloride, and then washed and dried.
Room temperature vulcanization
When room temperature vulcanization, the vulcanization process is carried out at room temperature and atmospheric pressure, such as using room temperature vulcanization rubber (mixed rubber solution) for bicycle inner tube joints, repair and so on.
Thermal vulcanization
Thermal vulcanization is the main method of vulcanizing rubber products. According to the different curing media and curing methods, thermal curing can be divided into three methods: direct curing, indirect curing and mixed gas curing.
(1) Direct vulcanization, the product is directly placed in hot water or steam medium for vulcanization.
(2) Indirect vulcanization. Products are vulcanized in hot air. This method is generally used for certain products with strict appearance requirements, such as rubber shoes.
(3) Mixed gas vulcanization, air vulcanization is used first, and then direct steam vulcanization is used. This method can overcome the shortcomings of steam vulcanization that affect the appearance of the product, and can also overcome the shortcomings of long heat curing time and easy ageing due to the slow heat transfer of hot air.