How does the material composition of rubber seals affect their oil resistance, acid and alkali resistance, and corrosion resistance?

Rubber Sealing Rings are widely used in industrial equipment, automobiles, home appliances, aerospace and other fields, playing the role of sealing, waterproofing, dustproofing and corrosion resistance. The material composition of the sealing ring directly determines its performance in different environments, especially its oil resistance, acid and alkali resistance and corrosion resistance. The materials commonly used in rubber sealing rings include fluororubber (FKM), nitrile rubber (NBR), silicone rubber (VMQ) and ethylene propylene rubber (EPDM). The different properties of these material components make the sealing rings show different tolerances in specific environments. This article will explore how the material composition of rubber sealing rings affects their oil resistance, acid and alkali resistance and corrosion resistance.

1. Oil resistance of rubber materials
Oil resistance is the key to the sealing effect of the sealing ring in oil media. The molecular structure of different rubber materials determines their tolerance to oil:

Nitrile rubber (NBR): Nitrile rubber has excellent oil resistance and is one of the most commonly used oil-resistant rubbers. Its molecular structure contains nitrile groups, which are highly polar and can effectively resist the erosion of various oil substances. Therefore, NBR seals are often used in lubricating oil, hydraulic oil and diesel environments, and are widely used in the automotive and machinery industries.

Fluororubber (FKM): The molecular structure of fluororubber has a high fluorine content, which makes it extremely oil-resistant and chemically stable. Its oil resistance is better than NBR, and it can withstand corrosion from a variety of oils including gasoline, diesel, mineral oil and synthetic oil, and still maintains good performance at high temperatures. Fluororubber seals are often used in harsh chemical environments and high-temperature environments.

Silicone rubber (VMQ): Silicone rubber has poor oil resistance and is not suitable for use in oil media. However, silicone rubber performs well in high and low temperature resistance and is suitable for use in oil-free or low-oil equipment and pipeline systems.

The molecular structure of different rubbers gives them different tolerance to oil substances, so when selecting materials, it is necessary to select the most suitable sealing ring material according to the oil contact situation.

2. Acid and alkali resistance of rubber materials
Acid and alkali resistance refers to the ability of rubber seals to remain stable in acidic or alkaline solutions without corrosion or dissolution. The acid and alkali resistance of different rubber materials varies greatly:

Ethylene propylene rubber (EPDM): EPDM is an excellent acid and alkali resistant rubber with strong tolerance to dilute acids, dilute alkalis and a variety of chemicals. Its molecular structure contains saturated carbon-hydrogen chains and is not easily corroded by acid and alkali media. EPDM seals are widely used in pipes and containers for acid and alkali liquids, and are suitable for chemical, medical and other industries.

Fluororubber (FKM): Fluororubber performs well in acid and alkali resistance, especially for strong acids, strong alkalis and strong oxidants. Its high fluorine-containing molecular structure makes it chemically inert, so fluororubber is the preferred material in highly corrosive environments.

Natural rubber (NR): Natural rubber has poor acid and alkali resistance, especially in strong acids and strong alkalis. It is easy to be corroded. Therefore, it is not recommended to use seals made of natural rubber in high acid and alkali environments.

Acid and alkali resistance is one of the important factors in selecting sealing rings. Generally speaking, EPDM and FKM are materials with strong tolerance to acid and alkali environments, while natural rubber, NBR and other materials are not suitable for use in strong acid and alkali environments.

3. Corrosion resistance of rubber materials
Corrosion resistance determines whether the sealing ring can maintain stable chemical properties when it comes into contact with corrosive chemicals (such as solvents and oxidants). The choice of rubber materials directly affects the corrosion resistance of the sealing ring:

Fluororubber (FKM): Fluororubber has extremely high corrosion resistance among many rubber materials. Its fluorine molecular structure gives it high chemical stability and can resist a variety of highly corrosive chemicals, such as chlorinated hydrocarbons, aromatic solvents and strong oxidants. Therefore, fluororubber sealing rings are widely used in corrosive media sealing in the chemical industry.

Ethylene propylene rubber (EPDM): EPDM has good corrosion resistance to many polar solvents, dilute acids and dilute alkalis, but performs poorly in some non-polar solvents such as mineral oil. Therefore, EPDM seals are suitable for some polar chemical environments, such as bleach and detergents, but are not recommended for use in oil environments.

Silicone rubber (VMQ): Silicone rubber has moderate corrosion resistance and is suitable for non-polar solvents, but performs poorly in acidic and alkaline solutions and oxidants. Therefore, silicone rubber seals are generally used in milder environments and are suitable for sealing applications in the food and pharmaceutical industries.

Materials such as fluororubber and EPDM are relatively strong in corrosion resistance, while materials such as silicone rubber and NBR are suitable for mildly corrosive environments.

4. How to choose a suitable sealing material?
When selecting rubber seal materials, it is necessary to comprehensively consider the temperature, pressure, type of chemical media in contact with the working environment, and the durability requirements of the application. Based on the performance characteristics of the above different materials, the following are some common selection suggestions:

High temperature and oil-resistant environment: Fluorine rubber (FKM) seals are recommended due to their excellent oil resistance and high temperature stability.
Acid and alkali environment: Choose ethylene propylene rubber (EPDM) or fluororubber (FKM) materials. EPDM has good acid and alkali resistance, while FKM can resist strong acids and alkalis.
Neutral environment, mild anti-corrosion requirements: You can choose silicone rubber (VMQ), which has good temperature resistance and moderate corrosion resistance.
Lubricating oil, mineral oil or synthetic oil environment: Nitrile rubber (NBR) is a cost-effective choice, especially at room temperature.