What is the method to increase the hardness of O-ring rubber?

O-ring is a kind of sealing product with simple appearance and structure, various specifications and a large number of needs.

The sealing quality life of O-rings depends on the dimensional accuracy and rubber material. Generally, the rubber material is required to have certain mechanical strength, tear resistance, good heat resistance, oil resistance, chemical resistance, and small compression set under the conditions of use, which are its main indicators.
According to the application requirements, there are generally heat and oil resistance requirements, and the most used rubber is nitrile rubber.
Acrylic rubber can be used for oil-resistant sealing products that require higher temperatures (such as 150～C—l90℃).

Fluorine rubber for oil-resistant rubber products that require higher temperatures, and silicone rubber for heat-resistant applications.
When the working pressure is high, the way to increase the hardness of the O-ring rubber is to increase the filling amount of carbon black, but the filling amount is too high, mixing is difficult, and the basic physical properties of the vulcanizate are damaged, and the rubber is prone to scorching.

In the case of using the same kind of rubber, such as nitrile rubber, in order to improve heat and oil resistance and reduce compression set, peroxide (such as using DCP) vulcanization system or effective sulfur vulcanization system (low sulfur and high acceleration) can be used . These two vulcanization systems can generate more carbon-carbon bond cross-linked structures and single-sulfur bond cross-linked structures, which can effectively improve the heat resistance and oil resistance of the vulcanizate and reduce the compression set.

In the filling and reinforcement system of heat-resistant and oil-resistant rubber formulations of O-rings, low-activity thermal black, spray carbon black or semi-reinforcing carbon black are often used. These carbon blacks are characterized by relatively coarse particles. , The rubber has good elasticity, low heat generation, low compression and permanent deformation, and can be filled in large quantities, reducing the cost of the rubber. For example, O-rings used in dynamic sealing conditions need to increase the tear resistance, and some high-activity high wear-resistant carbon blacks can be used together.

Fluorine rubber compound is a self-reinforcing rubber. If activated carbon black is filled, the mechanical properties of the compound will be reduced. Therefore, it is generally filled with a small amount of thermal black or spray carbon black with low activity and coarse particles.