Natural rubber has high mechanical strength and good hand elasticity. As a traditional rubber variety, it is widely used in the production of various high-grade rubber products. However, there is a side methyl group which is highly prone to rearrangement on the natural rubber main chain, so its heat resistance Very poor, difficult to use for a long time in an environment above 70 °C. It can be seen that improving the heat resistance of natural rubber is of great significance for further expanding the application range of natural rubber. How to solve the problem of poor heat resistance of natural rubber in actual production? How to do it?
1.Use with other rubber
The rubber variety fundamentally determines the heat resistance of rubber products. The natural rubber itself has poor heat resistance. The most direct way is to use rubber with good heat resistance.
(1) Synthetic rubber: 1 styrene-butadiene rubber has good compatibility with natural rubber, heat resistance is better than natural rubber, can be added to natural rubber to improve the heat resistance of natural rubber products; 2 isoprene rubber is “synthetic natural” "Rubber", which has the dual properties of natural rubber and synthetic rubber. It can also improve the heat resistance of natural rubber to a certain extent by using an appropriate amount of isoprene rubber in the formulation of natural rubber products.
(2) Recycled rubber: a new type of rubber resource processed from waste rubber and waste rubber products. 1 Isoprene reclaimed rubber processed from isoprene unvulcanized rubber compound and isoprene bottle cap stopper can be used instead of isoprene rubber in natural rubber products to improve rubber compound. High and low temperature resistance; 2 butyl reclaimed rubber processed from waste butyl inner tube retains good heat resistance of butyl rubber, and is more compatible with natural rubber than butyl rubber, so it can be added in natural rubber product formula. The right amount of butyl reclaimed rubber improves the gas resistance and chemical stability of the rubber product while improving the heat resistance of the rubber compound.
2. Choose a suitable vulcanization system
The vulcanization system determines the type of cross-linking bond of the vulcanizate. The type of cross-linking bond will directly affect the heat resistance of the rubber product. The higher the cross-linking bond energy, the better the heat resistance of the vulcanizate. Under normal circumstances, the carbon-carbon bond The thermal stability is superior to the monosulfide bond, and the thermal stability of the disulfide bond is superior to the polysulfide bond. In the formulation of natural rubber products, the rubber which is usually vulcanized by the effective vulcanization system and the semi-effective vulcanization system has better heat resistance than the conventional sulfur vulcanizate, because the cross-linking bonds produced by the common sulfur system are mainly polysulfide bonds. The cross-linking bonds produced by the effective vulcanization system are mostly monosulfide bonds and disulfide bonds.
In the actual application process, natural rubber products are not used under extreme conditions with extremely high temperatures (butyl rubber, EPDM rubber, etc. are generally used for rubber products with special heat resistance), so rubber products manufacturers By the above method, or by using synthetic rubber or reclaimed rubber, or adjusting the type and amount of the vulcanizing agent and the accelerator in the vulcanization system, the heat resistance of the natural rubber product can be improved to some extent. Among them, when a suitable type of reclaimed rubber is used in a natural rubber product, not only the heat resistance of the rubber product can be improved, but also the vulcanization process of the rubber compound can be improved, and the vulcanization reversion can be reduced.