In hydraulic, pneumatic, and fuel systems, rubber seals are critical to reliability. A single seal failure can lead to leaks, downtime, contamination, or even complete system failure.
One of the biggest challenges in these environments is chemical resistance — the ability of rubber materials to resist swelling, softening, or cracking when exposed to aggressive fluids.

Designing seals that last requires understanding how different compounds behave under chemical exposure and how to pair that with the right design and curing process.

Understanding Chemical Resistance in Rubber

Rubber’s performance in chemical environments depends on its base polymer structure and crosslinking chemistry.
Hydrocarbons, oils, and fuels tend to attack certain rubbers, breaking down molecular bonds or extracting plasticizers.
Choosing the wrong compound can quickly lead to seal degradation, leaks, and maintenance headaches.

When selecting materials, consider:

  • The type of fluid (hydraulic oil, brake fluid, fuel, coolant, etc.)
  • Operating temperature range
  • Pressure and mechanical load
  • Exposure duration and chemical concentration

Common Rubber Materials and Their Chemical Resistance

Here’s how common elastomers perform in fuel and hydraulic applications:

Nitrile Rubber (NBR)

  • Excellent resistance to petroleum oils, diesel, and hydraulic fluids
  • Poor resistance to ozone, UV, and polar solvents
  • Cost-effective and widely used for general hydraulic seals

Best for: hydraulic systems, oil seals, gaskets, O-rings

Hydrogenated Nitrile (HNBR)

  • Improved temperature and ozone resistance over standard NBR
  • Withstands hot oils and aggressive fuels
  • Excellent balance of strength and flexibility

Best for: automotive fuel systems, power steering, and high-pressure hydraulics

Fluorocarbon (FKM / Viton®)

  • Outstanding chemical resistance to fuels, solvents, and oils
  • Performs well at temperatures up to 200°C
  • Resistant to compression set and long-term aging

Best for: fuel injectors, aerospace, and chemical process equipment

EPDM Rubber

  • Resistant to water, steam, brake fluids, and polar chemicals
  • Not compatible with oils or fuels
  • Great for seals exposed to outdoor or water-based systems

Best for: brake systems, water-based hydraulic systems, outdoor gaskets

Fluorosilicone (FVMQ)

  • Combines the flexibility of silicone with the fuel resistance of FKM
  • Excellent performance across a wide temperature range
  • More expensive but ideal for extreme environments

Best for: aerospace fuel systems and specialty seals

Design Considerations for Chemical-Resistant Seals

Material choice is only part of the equation — design plays an equally critical role in seal longevity and performance.

1. Account for Swelling and Compression Set

Even resistant rubbers can swell slightly under long-term exposure.
Design grooves and clearances to tolerate this expansion without causing extrusion or sealing loss.

2. Maintain Proper Compression

Under-compressed seals can leak; over-compressed ones may take a permanent set.
A 20–30% compression range is typical for most elastomers, depending on hardness.

3. Optimize Seal Geometry

Rounded corners, smooth transitions, and proper lip design help maintain sealing under dynamic conditions.
Avoid sharp edges or stress points where tearing can start.

4. Consider Temperature and Pressure Effects

High temperatures accelerate chemical attack, while pressure cycles can cause extrusion or deformation.
Use backup rings or harder compounds for high-pressure applications.

Primo Rubber Co.: Your Partner in Chemical-Resistant Rubber Seals

At Primo Rubber Co., we specialize in custom rubber injection molding for high-performance sealing applications. Whether you’re designing a new hydraulic system or improving existing seals for longer life, our engineers can help you choose the right compound, geometry, and molding process to ensure chemical resistance and durability. All of our parts are manufactured in the USA under strict quality control, ensuring consistent, high-performance seals that last.

Contact Primo Rubber Co. today to discuss your project and find the ideal material and design solution for your chemical-resistant rubber seals.