Vacuum Seal Rings

When choosing materials for vacuum sealing rings, consider these crucial factors:

Gas Permeability

Gas permeability varies based on material (e.g., FKM/Viton® A, NBR, EPDM, fluorosilicone VFMQ, Viton GF, PTFE, silicone, FFKM/Kalrez®), hardness, pressure, temperature, and specific gases. For low permeability in vacuum applications, FKM vacuum O-rings (Viton® A) are most common. Other suitable materials include NBR, EPDM, VFMQ, PTFE, silicone, and FFKM. It’s vital to distinguish permeability from leakage.

Compression Set Recovery

A vacuum O-rings must fully rebound after compression release. Failures in rebound reduce sealing force and elevate the chance of leaks.

Outgassing

Plasticisers or low-boiling solvents in elastomers can outgas under vacuum. Materials made from pure polymers—without volatile components—minimise this effect. Outgassing can occur via bulk desorption, surface desorption, or evaporation.

Operating Temperature

O-rings for vacuum use must endure high operating temperatures. Each material has its own useful temperature range; excessive temperatures can cause degradation, swelling, or outgassing, often accompanied by compression set.

Surface Cleanliness

O-rings must be free from dirt, cracks, scratches, and maintain circular cross-sections to ensure proper sealing. Contaminated surfaces undermine performance.

Chemical Compatibility

Select a material that suits the chemicals and temperatures in your application. This is critical to avoid costly failures and maintain performance in aggressive environments.

Vacuum O‑Ring Properties

Vacuum sealing rings are designed to prevent air ingress. Typically rated at Shore A 65–80, they offer high contact area and lower thermal conductivity. Material choice depends largely on thermal compatibility.

Essential properties of vacuum O-rings include:

• Excellent gas impermeability

• Strong moisture resistance

• Low vapour pressure at operating temperature

• Absence of volatile substances under vacuum/heat

• Heat resistance

These rings are used in static seals in hydraulic or pneumatic systems, as well as dynamic seals in moving machine parts.

Common Vacuum O‑Ring Materials

FKM / FPM / Viton

FKM vacuum O‑rings resist mineral oils, silicone greases, fuels, benzine, alcohols, solvents, diluted acids/bases, propan/butan, glycol-based brake fluids, and ketones/esters. Their fluoropolymer composition makes them suitable for high-temperature and vacuum applications.

FEP/PFA Encapsulated O‑Rings

These combine an elastomer core (e.g., silicone or Viton) with a seamless FEP/PFA jacket. They deliver superior chemical compatibility, low permeability, and function across −60 °C to +260 °C, ideal for static sealing in automotive, chemical, or petrochemical use.

NBR

NBR vacuum O‑rings are valued for low permeability, excellent recovery after deformation, abrasion resistance, and performance with oils, greases, and chemicals. Commonly used in removable vacuum seals.

EPDM

EPDM O‑rings offer reversible elasticity, and resist weathering, organic/inorganic acids, alkaline cleaners, polar solvents, and ester-based hydraulic fluids. Rated from −40 °C to +110 °C (up to +150 °C), they are widely used in industrial environments.

Silicone (VMQ)

High-temperature silicone O‑rings operate from −50 °C to +300 °C. Their excellent sealing properties, UV stability, and low outgassing make them a reliable choice for vacuum conditions.

FFKM / Kalrez®

FFKM (Kalrez®) O‑rings offer outstanding chemical resistance (even to strong acids), heat tolerance to +325 °C, low swelling, and minimal permeability. Their self-extinguishing qualities and durability under hot air make them ideal for critical vacuum seals.

These materials suit both static and dynamic vacuum applications.

Power Rubber’s Vacuum O‑Ring Range

At Power Rubber, we offer an extensive range of high-performance vacuum O-rings, tailored to both static and dynamic requirements. Contact us for solutions designed to meet your application demands.

Get in touch for a quote or expert advice
Phone: +48 22 292 40 24 or +48 505 16 03 03
Email: Power@PowerRubber.com
Contact form available on our website