Silicone vs Viton: Comparing Heat-Resistant Rubber Above 180°C
Silicone or Viton for temperatures above 180°C? See the temperature range, ozone resistance and cost comparison.
About this article
This article was prepared by the technical team at Hamta Polymer Zayandeh Rood Industries. Contact our specialists for application guidance and the right option for your industrial need.
Silicone or Viton for temperatures above 180°C? See the temperature range, ozone resistance and cost comparison.
# Silicone vs Viton: Comparing Heat-Resistant Rubber Above 180°C
For applications above 180°C, two materials dominate the field: silicone (VMQ), with excellent heat resistance and flexibility at low temperature, and Viton (FKM), with even higher heat resistance plus superior chemical resistance. Getting this choice wrong usually means either paying for capability you don't need, or premature failure in a chemically aggressive environment. Below, we compare these two materials by temperature range, chemical resistance, and application.
This article is part of our Complete Guide to Rubber Seals; for the basics of O-ring types, start there first.
Table of Contents
- Why material choice gets trickier at high temperature
- What are silicone's (VMQ) key properties?
- What are Viton's (FKM) key properties?
- Silicone vs Viton comparison chart
- Which material fits your application?
- The common mistake in choosing heat-resistant material
- FAQ
Why Material Choice Gets Trickier at High Temperature
At high temperature, most general-purpose elastomers (like NBR or EPDM) quickly lose their elasticity, become hard and brittle, and eventually crack. Only a limited group of specialty elastomers — mainly silicone and fluoroelastomer — can run continuously above roughly 180–200°C. But despite sharing that heat resistance, these two materials differ substantially in other properties, which is exactly what makes this choice tricky.
What Are Silicone's (VMQ) Key Properties?
Thanks to its silicon-oxygen molecular backbone, silicone has an exceptionally wide operating temperature range (roughly -55°C to +220°C) and holds up very well against ozone, UV, and sunlight. Food-grade and pharmaceutical-grade silicone is also readily available. Its main weaknesses are poor resistance to oil, fuel, and most solvents, plus relatively lower tensile strength and abrasion resistance than other elastomers.
What Are Viton's (FKM) Key Properties?
Fluoroelastomer (FKM/Viton) offers high heat resistance (up to roughly +200°C) plus excellent chemical, oil, and fuel resistance, making it ideal for demanding industrial environments (petrochemical, automotive, aerospace). But FKM loses flexibility at low temperature (below roughly -20°C), and its price is noticeably higher than silicone's.
Silicone vs Viton Comparison Chart
| Property | Silicone (VMQ) | Viton (FKM) |
|---|---|---|
| Max continuous operating temp. | ~220°C | ~200°C |
| Min operating temp. | ~-55°C | ~-20°C |
| Ozone and UV resistance | Excellent | Excellent |
| Oil and fuel resistance | Poor | Excellent |
| General chemical resistance | Fair | Excellent |
| Relative cost | Medium | High |
| Typical application | Oven/baking equipment seals, food/pharma grade | Engine sealing, exhaust systems, petrochemical industries |
Which Material Fits Your Application?
If the environment is simply high-temperature and free of oil or aggressive chemicals (industrial baking equipment or home appliances, for instance), silicone is the more economical, flexible choice. But if the environment combines high temperature with exposure to engine oil, fuel, or chemicals (like a cylinder head gasket or exhaust system seal), Viton is the only reliable option.
The Common Mistake in Choosing Heat-Resistant Material
The most common mistake is choosing silicone purely for its heat resistance, without checking whether oil or fuel is present in the working environment; the usual result is fast swelling of the silicone part and premature leaks. Conversely, using FKM in simple food-grade applications that don't actually need chemical resistance drives up project cost for no technical reason.
FAQ
Is food-grade silicone available?
Yes — silicone is one of the most widely used food- and pharma-grade materials, and FDA certification is readily available for it.
Why did my silicone gasket fail on contact with engine oil?
Silicone has very poor resistance to petroleum oils; for this application you should use Viton (FKM) or NBR instead of silicone.
Does Viton still work below zero?
Standard FKM becomes hard and brittle below roughly -20°C; for applications combining low and high temperature, a specialty low-temperature FKM grade needs to be ordered.
Which is better for sealing a car's exhaust system?
Viton (FKM), thanks to its high resistance to heat, exhaust gases, and residual oil, is the automotive industry standard for this application.
Is Viton always more expensive than silicone?
Yes, typically — FKM carries a higher price than silicone due to its more complex manufacturing process and more expensive raw materials.
Sources & References
This guide draws on the ASTM D2000 industrial standard and the Parker O-Ring Handbook's technical guidance on the operating temperature of specialty elastomers.
Summary
For high temperature without oil or chemical exposure (food, baking, and appliance applications), silicone is the cost-effective choice. For high temperature combined with oil, fuel, or chemical exposure (automotive, petrochemical industries), Viton is the necessary, worthwhile investment. If you're not sure which material fits your project, our technical team offers a free consultation and price quote.
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