Common Rubber Materials for Skeleton Oil Seals and Their Performance?

Number of hits：622025-12-29 14:56:30　

When selecting a skeleton oil seal (also known as a radial shaft seal), the choice of material often has a greater impact on long‑term sealing reliability than the seal’s geometry. Different elastomers vary significantly in their resistance to temperature, oil, and aging, so understanding the performance range of each material is essential for determining whether a seal can withstand a specific operating environment. Common materials include nitrile rubber, fluoroelastomers, silicone rubber, hydrogenated nitrile, acrylic rubber, and PTFE. These compounds are widely used in industrial machinery, automotive powertrains, and hydraulic systems.

Nitrile rubber (NBR) is one of the most frequently used materials because it offers a practical balance of cost, oil resistance, and wear performance. It generally remains stable between –40°C and 125°C and performs well in contact with mineral oils, hydraulic fluids, and fuel oils. Its limitations become more apparent in high‑temperature or highly oxidative environments, which is why NBR is best suited for standard operating conditions rather than demanding applications.

For applications involving elevated temperatures or aggressive chemical exposure, fluoroelastomers (FKM) provide a more dependable option. They can typically withstand temperatures from –20°C to 250°C and are compatible with nearly all common lubricants, including oils containing extreme‑pressure additives. Their strong resistance to heat and chemicals makes them a preferred choice for engines, transmissions, and turbocharger areas, although the higher material cost must be considered.

Silicone rubber (VMQ) is known for its exceptionally wide temperature range, maintaining flexibility and stability from roughly –60°C to 225°C. It offers excellent resistance to heat, oxidation, and UV exposure, but its resistance to oils is relatively weak. As a result, silicone is better suited for hot water, steam, food‑grade environments, or dry‑air systems rather than applications where the seal is continuously immersed in oil.

When a combination of good high‑temperature performance and improved oil resistance is required—without reaching the cost level of fluoroelastomers—hydrogenated nitrile rubber (HNBR) becomes a practical compromise. With a typical operating range of –50°C to 150°C, HNBR provides better resistance to heat, wear, and aging than standard NBR. It is commonly used in automotive systems, construction machinery, and other high‑load equipment.

Acrylic rubber (ACM) performs well in high‑temperature oil environments and generally operates between –25°C and 150°C. Its heat resistance places it between NBR and FKM, making it suitable for transmission fluids, gear oils, and similar applications. However, its flexibility at low temperatures is limited, which restricts its use in colder climates.

For extreme conditions, such as high rotational speeds, elevated temperatures, or exposure to aggressive chemicals, PTFE is one of the most stable materials available. It can operate from –65°C to 260°C and is largely unaffected by oils or chemical media. Its low friction characteristics help reduce wear, but its lack of elasticity requires careful handling during installation, and the overall cost is higher than that of elastomer‑based seals.

Other materials may also be used for specific applications. Polyurethane (PU) offers excellent wear resistance and mechanical strength, making it suitable for high‑pressure or reciprocating motion. Ethylene‑propylene rubber (EPDM) performs well in water, steam, and polar solvents but is not suitable for oil‑based environments.

Overall, there is no universally “best” material for every shaft seal. The optimal choice depends on the actual operating conditions of the equipment. Each elastomer has its own strengths, and when the material is matched appropriately to the application, the seal can maintain reliable performance throughout its service life.