What are the ways to make rubber hardness increase?

First, rubber raw glue

The formulation of high hardness rubber often requires a large amount of filling and reinforcing agent, and the selection of raw rubber should choose the brand of high Mooney viscosity. For example, EPDM should choose a brand with high Mooney and high ethylene content; NBR can choose high Menni, high acrylonitrile content brand. Sometimes according to the needs of other properties, you can choose to use high and low Mooney glue, low Mooney glue is not conducive to a large number of filling.

Second, reinforcing filler

Reinforcing with carbon black and white carbon black is the best choice, the comprehensive performance of the two is better, the ability to increase hardness is strong, and the effect of fine particle carbon black is the best, but high hardness rubber material needs a lot of filling, if you use fine particle carbon black alone, rubber mixing, vulcanization and other processes will have serious problems, so fine particle carbon black and large particle carbon black combined use the best effect. Such as N330/N550 collocation. Other weak reinforcing fillers should not be used as far as possible, because these fillers have a weak ability to increase hardness, and a larger number of fillers are needed to achieve the target hardness than carbon black and white carbon black, resulting in a decline in the comprehensive performance of the rubber and the process performance.

Third, plasticizer

High hardness compound requires a lot of filling reinforcing agent, resulting in rubber mixing, vulcanization and other process problems, the right amount of plasticizer or to add, although the plasticizer will reduce the hardness of the compound. The selection of plasticizers is appropriate for solid plasticizers, such as solid coumaron.

Fourth, curing agent

Increasing the crosslinking density of the compound is beneficial to improving the hardness of the compound. For sulfur vulcanization system, increasing the amount of accelerators, especially TMTD accelerators, is conducive to improving the hardness. The increase in the amount of vulcanization can also improve the cross-linking density and enhance the hardness of the rubber, such as when the amount of sulfur reaches 30 to 50 mass parts, hard rubber can be prepared, but when the amount of sulfur and the amount of accelerator are increased, it is easy to produce frosting phenomenon, and the amount needs to be balanced. In addition, for sulfur vulcanization system, high hardness rubber due to high filling, mixing and vulcanization processing heat increase, easy to cause scorch phenomenon, so for the sake of insurance, with anti-scorch agent is also of great benefit, such as CTP.

Silicone foam board

For the peroxide vulcanization system, increasing the amount of peroxide can improve the hardness, but not too high, you can choose a variety of peroxide vulcanization agents and use, in addition to the addition of crosslinking agents can significantly improve the cross-linking density of the rubber, such as DCP vulcanization agent, can add TAIC, PDM (HVA-2), TAC, PL-400 (TMPTMA), Of course, sulfur can also be used as a cross-linking agent.