Natural rubber has high mechanical strength, good elasticity but poor ozone resistance and aging resistance; EPDM rubber with excellent aging resistance, high and low temperature resistance can be used with natural rubber to prepare a rubber compound with better comprehensive performance, and extend the use of natural rubber products Longevity, the selection of a suitable compounding system is of great significance to improve the performance of natural rubber/ethylene propylene rubber blends. So what should be paid attention to when designing the compound compound formula? How to choose natural rubber/ethylene propylene rubber blending compound system?
1. The significance of the combined use of natural rubber and EPDM
Natural rubber contains a large number of carbon-carbon double bonds as the active points of the crosslinking reaction, giving natural rubber good physical and mechanical strength and adhesion properties, but the rubber has poor heat resistance and aging resistance; compared with natural rubber , The main chain of highly saturated EPDM rubber is composed of chemically stable saturated hydrocarbons. It has excellent heat resistance and aging resistance but poor self-adhesiveness and mutual adhesion. The combined use of natural rubber and EPDM rubber can not only improve the aging resistance of natural rubber, but also solve the problem of poor viscosity of EPDM rubber.
2. The combined effect of natural rubber/ethylene propylene rubber blends in different proportions
When natural rubber and EPDM are used together, the structure difference between the two is very large, and the ratio of the combined use directly affects the performance of the combined rubber. Natural rubber is mixed with a small amount of EPDM rubber and used together. Natural rubber will form the continuous phase and EPDM rubber will form the dispersed phase. When EPDM rubber is used with a small amount of natural rubber, natural rubber will form the dispersed phase. Ethylene-propylene rubber is a continuous phase; the dispersed phase particle size of EPDM rubber is larger than that of natural rubber. Generally, the particle size of the dispersed phase of EPDM rubber is about 3μm, and that of natural rubber. About 0.8μm. When the amount of natural rubber becomes larger and larger, the natural rubber is in a continuous phase, and the aging resistance of the combined rubber becomes worse and worse.
3. How to improve the blending effect of natural rubber/ethylene propylene rubber blends
Natural rubber and EPDM rubber have obvious structural differences, and there are big differences in compatibility and vulcanization properties. Only when the two are co-vulcanized can a good combination effect be obtained. The vulcanization speed of natural rubber is much faster than that of EPDM rubber. The solubility of the vulcanizing agent and accelerator 2LLYY723 in the two rubbers is different. They usually diffuse from the EPDM rubber phase to the natural rubber phase, thereby affecting the two mixed rubbers. The vulcanization speed of the material; natural rubber with different structures and EPDM rubber will form a heterogeneous system after blending, and the blending ratio and viscosity ratio affect the properties of the blended rubber.
Rubber product manufacturers need to adjust the vulcanization characteristics of natural rubber and EPDM to keep the same to achieve co-vulcanization. Rubber product manufacturers can blend natural rubber with sulfur, EPDM rubber and plasticizer PIB/vulcanizing agent DCP to make a masterbatch and adjust the viscosity of the rubber, and blend in a certain proportion according to the viscosity of the masterbatch to improve Co-vulcanization and blending effect of natural rubber/EPDM rubber.
In actual production, there are many problems that need to be solved in the blending of natural rubber and EPDM rubber. Rubber product manufacturers can also replace the natural rubber in the formula with natural latex reclaimed rubber. Compared with natural rubber, the blending effect of reclaimed latex rubber and EPDM rubber is better, and the price is lower. It can effectively improve the comprehensive index of the blended rubber and reduce the cost of raw materials.