Characteristics and performance table of Nitrile Rubber

Detailed explanation of the characteristics of nitrile rubber

Nitrile rubber is a copolymer of butadiene and acrylonitrile, and its combined acrylonitrile content has a significant impact on its mechanical properties, adhesive properties, and heat resistance. In terms of the characteristics of butadiene and acrylonitrile monomers, butadiene has weaker polarity, while acrylonitrile has stronger polarity. Therefore, the more acrylonitrile content on the main chain of nitrile rubber, the worse the flexibility of the main chain. The higher the low-temperature brittleness temperature, the worse the low-temperature resistance performance; On the other hand, acrylonitrile has good heat resistance because during the heating process, acrylonitrile in nitrile rubber can generate alcohol soluble substances to inhibit thermal oxidative degradation. Therefore, the heat resistance of nitrile rubber increases with the increase of acrylonitrile content; Meanwhile, due to the polarity factor of acrylonitrile, increasing the content of acrylonitrile can improve the adhesive strength of nitrile rubber. Therefore, it is very important to test the content of bound acrylonitrile in nitrile rubber.

The content of acrylonitrile has a significant impact on the performance of NBR. The acrylonitrile content of general acrylonitrile nitrile rubber is between 15% and 50%. If the acrylonitrile content increases to over 60%, it will harden, similar to leather, and no longer have rubber properties.

1. Oil resistance and solvent resistance: Nitrile rubber has oil resistance in ordinary rubber. Nitrile rubber is more resistant to petroleum based oils, benzene, and other non-polar solvents than natural rubber, styrene butadiene rubber, butyl rubber, and other non-polar rubbers, but it is also better than polar chlorinated rubber. However, nitrile rubber has poor resistance to polar oils and solvents (such as ethanol), but poor resistance to non-polar rubber.

2. Physical performance characteristics: Nitrile rubber is a random structure of nitrile copolymers that does not crystallize under tension. Therefore, the physical and mechanical properties of pure nitrile rubber vulcanized rubber are the same as those of styrene nitrile rubber, far lower than natural rubber. After adding reinforcing fillers such as carbon black and phenolic resin, the tensile strength of nitrile vulcanized rubber can reach the level of natural rubber, usually around 24.50mpa. As the polarity content of the NBR increases, the flexibility of the macromolecular chain decreases, the atomic force between molecules increases, double bonds decrease, and the macromolecular chain is unsaturated, resulting in a series of performance changes. When the ACN content is between 35% and 40%, it is the critical point for compression deformation, elasticity, and hardness at 75 ℃. If the oil resistance meets the requirements, varieties with ACN less than 40% should be used as much as possible. The elasticity of nitrile rubber is smaller than that of natural rubber and styrene butadiene rubber. The elasticity of NBR is closely related to temperature. Compared to NBR, the likelihood of temperature and elasticity increase is greater. Therefore, nitrile rubber is very suitable for manufacturing shock absorbers with high oil resistance. The characteristics of the elasticity of nitrile rubber changing with the binding of acrylonitrile

3. Breathability: Nitrile rubber has better air tightness than natural rubber and styrene butadiene rubber, but it is not as good as polysulfide rubber, which is similar to butyl rubber.

4. Low temperature performance: Nitrile rubber has poor low-temperature performance in general rubber. The low-temperature performance is related to the content of acrylonitrile, and the glass transition temperature increases with the increase of acrylonitrile content. It can reduce the glass transition temperature of nitrile rubber and improve its low-temperature performance.

5. Heat resistance: Nitrile rubber has better heat resistance than natural rubber and styrene butadiene rubber. By selecting the appropriate formula, nitrile rubber products can be used continuously at 120 ℃; Can withstand hot oil at 150 ℃; After soaking in oil at 191 ℃ for 70 hours, it still has the ability to bend. 6. Ozone resistance: Nitrile rubber has poor ozone resistance and is generally improved by adding ozone resistant agents. However, products that come into contact with oil during use are prone to removing the ozone resistant agent and losing its ozone resistance. Combined with PVC, the effect is significant.

7. Water resistance: Nitrile rubber has better water resistance. The higher the content of acrylonitrile, the better its water resistance.

8. Electrical insulation performance: Nitrile rubber has poor electrical insulation performance due to its polarity. It belongs to semiconductor rubber and should not be used as insulation material.

9. Aging resistance: NBR without anti-aging agents has very poor aging resistance, while NBR with anti-aging agents has better aging and heat resistance than natural rubber. After thermal oxidative aging, the tensile strength of natural rubber significantly decreases, but the decrease in nitrile rubber is actually very small.

The heat resistance of nitrile rubber is the same as its aging resistance. When L0000H ages at 100 ℃, its elongation can still exceed 100%. Nitrile rubber products can be used for a short period of time at 130 ° C and can be used at higher temperatures without oxygen. Therefore, nitrile rubber has better heat resistance than natural rubber and styrene butadiene rubber. Even more than chloroprene rubber. Nitrile rubber has the same weather and ozone resistance as natural rubber, but slightly lower than natural rubber. Adding polyvinyl chloride to nitrile rubber can improve its weather resistance and ozone resistance.

10. Radiation resistance:

Nitrile rubber may also be damaged under nuclear radiation, leading to an increase in hardness and a decrease in elongation. However, compared to other synthetic rubbers, NBR is less affected by radiation, and NBR with an acrylonitrile content of 33% -38% has good radiation resistance. After nuclear radiation, the tensile strength of NBR with high acrylonitrile content can be increased by 140%. This is because NBR with low acrylonitrile content will degrade under radiation, while NBR with high acrylonitrile content will undergo crosslinking reaction under nuclear radiation.

Performance Table of Nitrile Rubber

Material properties of commonly used synthetic rubber