How to choose special rubber for different parts of the car?

Due to the excellent performance of special rubbers, they are widely used in the automotive industry, with common applications including FKM, NBR, ACM, VMQ, etc. Different specialty rubbers offer various performance advantages and strengths. Therefore, determining the appropriate rubber material for different parts of the car is a crucial consideration for car manufacturers.

 

This article elaborates on the characteristics of different special rubbers and their specific requirements for various automotive applications.

 

1. FKM (Fluoroelastomer)

Fluoroelastomer refers to a synthetic polymer elastomer containing fluorine atoms on its main or side chains. This rubber exhibits several excellent properties relevant to the automotive industry:

 

General Physical and Mechanical Properties.

Fluoroelastomers generally have high tensile strength and hardness but low elasticity. The friction coefficient is around 0.8, and they exhibit good wear resistance, although their performance on smooth metal surfaces is poor.

 

Heat and Temperature Resistance.

Fluoroelastomers demonstrate significant aging resistance comparable to silicone rubber. However, their mechanical properties, including tensile strength and hardness, decline notably with increasing temperatures. Below 150°C, these properties decrease rapidly; between 150°C and 260°C, the decrease is more gradual.

 

Corrosion Resistance.

Fluoroelastomers are exceptionally resistant to corrosion, surpassing other rubber types in stability against organic liquids (such as fuel oil, solvents, hydraulic fluids), concentrated acids (nitric acid, sulfuric acid, hydrochloride acid), high concentrations of hydrogen peroxide, and strong oxidants.

 

Compression Set.

They exhibit good resistance to compression set, which is critical for automotive seals.

 

Other Properties: Fluoroelastomers have poor cold resistance.

 

In summary, Fluoroelastomers can be applied to nearly all automotive parts, but due to their high cost, they are generally reserved for applications demanding superior performance, such as in oil seals.

 

2. ACM (Acrylic Rubber)

Acrylic rubber's structure and polar ester side chains contribute to its primary properties: excellent heat and oxygen aging resistance, and good oil resistance. However, it has poor resistance to cold temperatures, water, and solvents.

Acrylic rubber is extensively used in products requiring high-temperature and oil resistance. It ranks second only to Fluoroelastomers in comprehensive heat and oil resistance among raw rubber varieties. It is particularly suitable for manufacturing rubber oil seals, O-rings, gaskets, and hoses operating at temperatures up to 180°C. Acrylic rubber is a practical choice when usage conditions are not extremely stringent and the use of fluorine-based adhesives is not economical.

Internationally, acrylic rubber dominates various automotive sealing applications and is recognized as an automotive-grade rubber.

 

3. NBR (Nitrile Rubber)

Nitrile rubber offers excellent oil resistance, second only to polysulfide rubber and Fluoroelastomers, and superior to chloroprene rubber. However, it lacks resistance to high temperatures. With an appropriate formulation, it can withstand temperatures up to 130°C and up to 150°C in hot oil. Common applications of nitrile rubber include gaskets, washers, and rubber hoses.

 

4. VMQ (Silicone Rubber)

 

Silicone rubber excels in high and low-temperature resistance, with a working temperature range of -100°C to 350°C. It also exhibits excellent resistance to ozone aging, oxygen aging, and weathering. In the automotive industry, silicone rubber is commonly used for rotary shaft seals and spark plug sleeves.

 

Summary:

Based on the performance characteristics of these materials, the above four rubbers can meet the majority of automotive application requirements. However, for specific conditions, careful consideration of their unique properties is essential. For instance, prioritize silicone rubber in low-temperature environments, use nitrile rubber cautiously in high-temperature applications, and manage the use of Fluoroelastomers due to their higher cost.