Zinc oxide is a commonly used active agent in rubber processing. In the rubber production, waste and recycling process may release zinc compounds, causing harm to the environment, so the amount of zinc oxide in the rubber formula should be reduced. active zinc oxide has a small particle size, large surface area, high vulcanization activity, compared with ordinary zinc oxide, the amount of active zinc oxide is reduced, thus reducing the harm of zinc to the environment, reflecting the environmental and economic benefits.
Active zinc oxide is produced using a wet process, a combination of precipitation and roasting, to produce active zinc oxide and transparent zinc oxide, as opposed to the traditional indirect calcination process used by many other producers. The wet process has a high degree of consistency in quality, the process also results in a large specific surface area (40m2/g) and an optimal particle size distribution for many applications, and the low content of heavy metal impurities is one of the environmental guarantees of this product.
The production process of the wet process is as follows: zinc ingot and sulfuric acid reaction to generate zinc sulfate, and then its reaction with sodium carbonate to produce zinc carbonate as raw material for zinc oxide. With zinc carbonate as raw material, zinc oxide is produced by washing, drying, calcining and crushing.
The average particle size of active zinc oxide is 50nm, the specific surface area is large, about 40m2/g, and the crystals are honeycomb, loose and porous, so the dispersion is good; its diffusion speed is faster than ordinary zinc oxide, distribution is uniform, in the reaction to improve the phenomenon of bridging agglomeration, basically can be reacted completely; heavy metals Pb2 +, Cu2 +, Cd2 +, Mn2 +, Fe2 + content is very low, in line with the requirements of environmental protection.
Product Use
Zinc oxide in the rubber industry is mainly used as rubber vulcanization active agent (accelerating agent), the function of which is to enhance the activation of vulcanization accelerator and improve the vulcanization effect of rubber. Its reaction mechanism is: zinc oxide and accelerator chemical reaction to generate accelerator zinc salt; accelerator zinc salt and polysulfide molecules to generate polysulfide zinc salt; polysulfide zinc salt and rubber macromolecule reaction to complete the final chemical crosslinking, so as to promote the vulcanization of the rubber, activation and strengthening of the role of anti-aging, to achieve stability, processing safety, a large degree of reduction in the defective rate, and to improve the rubber products, tear resistance, abrasion resistance, and increase the fixed elongation of vulcanized rubber, and increase the effect of rubber vulcanization. And improve the vulcanized rubber stretch stress, tensile strength and elongation, reduce compression permanent deformation, etc.
1. Active zinc oxide in the semi-steel radial tire innerliner application
In the same amount of conditions, the use of active zinc oxide 2 # formula rubber curing speed than the use of ordinary zinc oxide 1 # formula rubber increased by about 1 times; 3 # formula of active zinc oxide dosage is only 1 # formula of ordinary zinc oxide dosage of 80%, but the 3 # formula rubber curing speed is still much faster than the formula of the rubber l. 3 formulations of rubber coking properties, the Menni viscosity is not much difference.
Test formula vulcanized rubber hardness, constant tensile stress, tensile strength and tear strength than the production formula vulcanized rubber improved, fatigue resistance and flexural performance level is comparable, heat and air aging performance decreased slightly.
active zinc oxide instead of ordinary zinc oxide used in semi-steel radial tire inner ply rubber, curing rubber physical properties and the use of ordinary zinc oxide curing rubber level is comparable to that of the rubber, rubber vulcanization speed is accelerated, which is conducive to shorten the vulcanization time. The use of active zinc oxide can reduce the amount of zinc oxide, more adaptable to the requirements of environmental protection.
2. The application of active zinc oxide in radial tire tread rubber
With the increase in the amount of active zinc oxide, TC10 and TC90 overall trend of growth. ML and MH did not change much. This means that active zinc oxide can be used in a reduced amount.
The tensile strength, 100% elongation, 300% elongation and tear strength of the rubber did not change significantly with the increase in the amount of active zinc oxide. When the dosage exceeds 5 parts, the tear strength of vulcanized rubber decreases instead, which is caused by the excessive increase of crosslink density. After aging at 100℃×24h, the performance retention rate of the rubber compound with 3 parts of active zinc oxide is the best, and that with 2.5 parts of dosage is the worst. The reason may be the amount of 2.5 parts, the vulcanized rubber mesh structure is not perfect, which is also reflected in the same elongation at the tear, permanent deformation at the tear, Shore hardness, and compression heat generation performance.
Addition of active zinc oxide rubber blend, TC10 and TC90 significantly longer, the minimum torque ML, the maximum torque Mn and the difference between the two MH a ML increase, indicating that its processing safety, vulcanization speed slower, the degree of cross-linking increased, its tensile strength, 100% fixed elongation, 300% fixed elongation and tear strength have been improved, 100 ℃ × 24h aging, the specimen properties of the retention rate significantly After aging at 100℃×24h, the retention rate of specimen performance is significantly improved. When the active zinc oxide is used in reduced amount, TC90 - TS1 shortens, ML and MH changes are not significant, and the mechanical properties of the vulcanized rubber changes are not obvious; 2.5 parts of the dosage, the aging resistance of the vulcanized rubber decreases, so the amount can be reduced to 3 parts of the dosage to be used.
Advantages of zinc oxide
Through the experimental data of the above products, it can be learned that active zinc oxide can be widely used in various rubber products.
(1) It has good dispersion in the rubber material, and the physical and mechanical properties are improved;
(2) In the vulcanization process. The coking time of the rubber material becomes longer, the safety of vulcanization is improved, and the efficiency of vulcanization is improved;
(3) Due to the large specific surface area and small particle size of active zinc oxide, it can be used in a reduced amount in the addition of some rubber materials.
