50% of the industrially produced zinc oxide flows to the rubber industry. Zinc oxide and stearic acid are important reactants for rubber vulcanization and are one of the raw materials for rubber manufacture. The combination of zinc oxide and stearic acid enhances the degree of hardening of the rubber. Zinc oxide is also an important additive for automotive tires. In addition to vulcanization, zinc oxide can greatly improve the thermal conductivity of rubber, which helps the heat dissipation of the tire and ensures safe driving. Zinc oxide additives also prevent the erosion of rubber by mold organisms or ultraviolet light.
(1) The role of zinc oxide in the rubber tire industry (high-grade black and dark rubber tires, radial tires): improve the thermal conductivity, wear resistance, tear resistance, tensile strength and other indicators of the product, and save zinc oxide consumption About 30%.
(2) The role of zinc oxide in rubber products:
1 Active zinc oxide is mainly used as a reinforcing agent for rubber, so that the rubber has good corrosion resistance, tear resistance, elasticity and elongation.
2 Promoter for rubber vulcanization process, it is a multifunctional rubber compounding agent, mainly used as vulcanization active agent and reinforcing agent for natural rubber, synthetic rubber and latex.
3 When used as a vulcanization activator, it is evenly distributed in the rubber compound, and has a large contact area with hydrogen sulfide. The opportunity for interfacial reaction is large, and the active zinc oxide product has a catalytic effect of active substances to convert zinc oxide. It has a high conversion rate of zinc sulfide.
4 As a sulfurized oxidant, its role is to increase the activity of the accelerator, reduce the amount of accelerator, and shorten the curing cycle.
5 can speed up the vulcanization speed, improve the thermal conductivity of the vulcanized rubber, and make the vulcanization more thorough.
6 In the rubber industry, especially in the production of transparent rubber products, active zinc oxide is an excellent vulcanization activator.
(3) Zinc oxide acts in synthetic rubber: as an activator, a vulcanization accelerator and a reinforcing agent, and has a coloring effect. Promote the vulcanization, activation and reinforcement of the rubber, anti-aging effect, can strengthen the vulcanization process, improve the tear resistance and wear resistance of rubber products.
(4) The role of zinc oxide in natural rubber: as a vulcanization activator, promote the vulcanization, activation and reinforcement of the rubber, anti-aging effect, strengthen the vulcanization process, improve the tear resistance and wear resistance of rubber products.
(5) The role of zinc oxide in natural latex: act as an activator to promote the vulcanization, activation and reinforcement of the rubber, anti-aging effect, strengthen the vulcanization process, and improve the tear resistance and wear resistance of rubber products.
(6) The role of zinc oxide in white latex: as a coloring agent and filler.
(7) The role of zinc oxide in neoprene: as a vulcanizing agent and a compounding agent to increase thermal conductivity.
(8) The role of zinc oxide in the footwear industry (rubber shoes, rain boots, rubber gloves and other labor insurance products) (rubber shoes, rain boots, rubber gloves and other labor insurance products): improve wear resistance and anti-aging, and extend the service life.
(9) The role of zinc oxide in transparent rubber and rubber products for food: an essential inorganic active agent.
(10) The role of zinc oxide in transparent and translucent rubber: as a vulcanization activator.
(11) The role of zinc oxide in transparent or colored rubber products: it has an irreplaceable role as a traditional active agent such as carbon black.
Mechanism of action of zinc oxide in rubber
In the vulcanization process, zinc oxide reacts with promoters, sulfur, stearic acid, rubber macromolecular chains and corresponding intermediates, indicating that zinc oxide has a complex activation promoting effect. However, a large number of experimental results show that zinc oxide as a vulcanization activator mainly affects the formation speed of chemical association, the type and amount of cross-linking bonds in the vulcanization process, and thus improves the cross-linking degree of vulcanized rubber.
Since zinc oxide has a large affinity for electrons, the ability of the adsorption promoter is strong, and a zinc salt of a promoter which is soluble in the rubber is formed by the action of stearic acid, thereby improving the solubility and forming a kind with an amine or a fatty acid. The zinc complex makes the accelerator more active. Sulfur is added to the complex to form a strong vulcanizing agent by inducing activation. During this process, the surface of the zinc oxide particles continuously reacts, the particle size is continuously reduced, and zinc oxide is consumed until the compound is sufficiently vulcanized.
The conventional amount of 5 parts is the maximum amount of vulcanization fully activated based on a specific zinc oxide particle size. As the particle size of zinc oxide changes, its specific surface area and structure determine the activation of vulcanization.
Effect of Zinc Oxide on Process Properties of Rubber Compounds
The basic properties of zinc oxide mainly include the specific surface area and structure of the particles, which have a great influence on the rubber processing process, especially for processes such as mixing and vulcanization.
The mixing time of zinc oxide in rubber is closely related to its specific surface area and structure. Although it is easy to mix during mixing, it is difficult to disperse or it is easy to produce a gel. Nano-zinc oxide has a highly active surface which is highly agglomerated and agglomerated due to its large specific surface area and interfacial effect, which inevitably affects its dispersibility. To this end, Shanghai Yingdong Chemical Technology Co., Ltd. surface modification of nano zinc oxide to improve its dispersion in the rubber compound. In addition, the manufacturer should also rationally optimize the mixing process, improve the preparation of the masterbatch and the order of feeding, in order to fully improve the dispersion of nano zinc oxide. Replacing indirect zinc oxide with nano-zinc oxide can increase the Mooney viscosity and minimum torque of the rubber to different degrees, indicating that the surface structure of nano-zinc oxide enhances the physical adsorption and chemisorption of the rubber macromolecular chain.