Elastomer Selection Guide: Navigating Compound Engineering

In industrial sealing, specifying the correct elastomer compound is the difference between seamless machine operations and catastrophic system failure. When designing seals, engineers must evaluate chemical exposure, thermal limits, mechanical loads, and pressure spikes.

Below, we break down the four most critical compounds utilized in modern sealing applications:

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1. NBR (Nitrile Butadiene Rubber)

Nitrile is the workhorse of the seal industry. Offering excellent resistance to petroleum-based oils, water, and hydraulic fluids, it is the primary choice for standard cylinders.

• Temperature Range: -30°C to +100°C
• Best Used For: General purpose hydraulic seals, oil gaskets.
• Limitations: Poor resistance to ozone, weathering, and polar solvents.

2. FKM / Viton (Fluorocarbon Elastomers)

When systems run hot or encounter aggressive chemicals, FKM is the premier choice. Sourced from global suppliers, it maintains sealing integrity under severe conditions.

• Temperature Range: -20°C to +200°C (spikes to +250°C)
• Best Used For: Chemical processing pumps, aerospace engines, high-temp hydraulic machinery.
• Limitations: Vulnerable to low-molecular-weight organic acids and steam.

3. EPDM (Ethylene Propylene Diene Monomer)

EPDM provides outstanding resistance to ozone, sunlight, water, and steam. It is ideal for outdoor applications and hot-water environments.

• Temperature Range: -50°C to +150°C
• Best Used For: Outdoor enclosures, steam lines, automotive coolant hoses.
• Limitations: Absolutely no compatibility with petroleum oils, greases, or fuels.

4. PU (Polyurethane)

PU is highly prized for its mechanical strength, abrasion resistance, and outstanding tensile properties. In CNC-machined custom seals, PU block components offer zero tool-cost capabilities.

• Temperature Range: -30°C to +90°C
• Best Used For: High-pressure hydraulic cylinders, scrapers, wear rings.
• Limitations: High susceptibility to water hydrolysis at elevated temperatures.

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Technical Summary

• High Chemical Exposure: Use FKM / Viton
• Mechanical Shock / Wear: Use Polyurethane (PU)
• Steam & Weathering: Use EPDM
• Standard Hydraulic Oil: Use Nitrile (NBR)

Selecting the correct compound extends seal lifespan, reduces machine downtime, and optimizes system efficiency. Contact our engineering desk at CR Rubber and Seals for custom compound formulations.