FKM vs Silicone vs NBR vs EPDM: Material Selection

Specifying a rubber part usually comes down to one question: which elastomer survives the media, temperature, and mechanical load without failing early? This guide compares the four most common sealing elastomers – FKM, silicone, NBR, and EPDM – so you can pick the right one quickly.

The Four Workhorses

• FKM (Viton) – fluorocarbon; best for oil, fuel, and heat.
• Silicone (VMQ) – widest temperature range, low strength, poor oil at high temp.
• NBR (Buna-N) – cheap, oil-resistant, poor weather and ozone.
• EPDM – excellent weather, steam, and water; destroyed by oil.

Temperature Comparison

Chemical Resistance at a Glance

How to Choose

• Oil & fuel, high heat – FKM.
• Extreme cold or food/medical, low mechanical load – Silicone.
• Cost-sensitive, oil contact, moderate temp – NBR.
• Water, steam, outdoor, brake fluid – EPDM.

When One Elastomer Is Not Enough

For mixed conditions – for example oil plus steam – consider a specialty such as HNBR or a fluorosilicone blend. Our material specification library lists temperature, hardness, and compatibility for every compound we mold.

FAQ

Is FKM better than NBR?

For heat and aggressive chemicals, yes. For cost and general oil sealing at moderate temperature, NBR is the practical choice.

Why not use silicone for everything?

Silicone is weak and tears easily under dynamic load or high pressure; it also swells in oil at temperature. It excels at temperature extremes and static seals.

Can EPDM touch oil?

No. EPDM swells and fails in petroleum oil and fuel. Keep it for water, steam, and weather.

Related Resources

• FKM Chemical Compatibility – detailed fluid ratings.
• AS568 O-ring size chart – match your size.
• O-Ring Gland Design – groove and squeeze basics.