How to Choose the Right Seal Material for Your Solenoid Valve？
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The seal is the most critical—and most overlooked—component in a solenoid valve. It's what actually stops the flow when the valve closes. Choose the wrong seal material, and you'll get leaks, swelling, hardening, or complete valve failure. This guide breaks down the four seal materials available in U.S. Solid solenoid valves—NBR, EPDM, Viton™, and PTFE—and shows you exactly how to pick the right one for your application.
1. Understanding Seal Material Ratings
Seal compatibility is measured by volume swell—how much the seal material expands when exposed to a specific chemical. Less swell means better compatibility. The industry standard (used by Chemours and major elastomer manufacturers) rates materials from A to D:[1]
2. The Four Seal Materials
- Best value among the four materials — go-to choice for general industrial use
- Excellent resistance to petroleum oils, hydraulic fluids, fuel oils, and lubricants
- Good mechanical strength and abrasion resistance
- Available across virtually all U.S. Solid valve sizes and configurations
Weakness: Poor ozone and UV resistance. Not suitable for steam service — when exposed to steam, particularly above 212°F (100°C), NBR undergoes rapid hydrolytic degradation: the rubber absorbs moisture, swells significantly, and loses tensile strength and sealing force. While certain low-hardness NBR compounds can tolerate brief, incidental contact with low-pressure steam (<15 psi), this is not recommended for any continuous or high-pressure steam application. Also avoid ketones, esters, chlorinated solvents, and strong acids — NBR will swell and deteriorate rapidly in these environments.
- The best choice for steam and saturated steam applications up to 300°F
- Outstanding resistance to UV, ozone, and outdoor weathering — ideal for exposed installations
- Safe for potable water and food-grade applications (verify certification requirements)
- Handles phosphate ester hydraulic fluids (Skydrol, etc.) — Viton™ and NBR cannot
Weakness: NOT compatible with petroleum oils, fuels, or lubricants — this is a fundamental, non-negotiable incompatibility. EPDM has a fully saturated polymer backbone (only carbon-carbon bonds, no polar groups), which makes it chemically similar to hydrocarbon fluids. According to the "like dissolves like" principle,[2] non-polar petroleum molecules readily absorb into EPDM's non-polar polymer chains, causing the material to swell by 50% or more, lose tensile strength, and fail to maintain sealing force. This is not a matter of concentration or exposure time — even brief contact with petroleum oil will begin to degrade an EPDM seal. Never use EPDM in oil, fuel, or lubricant service under any circumstances.
- Widest temperature range among elastomer seals — outperforms NBR and EPDM at temperature extremes
- Superior resistance to petroleum products, aromatic hydrocarbons, and a broad range of industrial chemicals
- Excellent ozone and UV resistance for outdoor or exposed applications
- Industry-standard choice for chemical processing, aerospace, automotive, and fuel systems
Weakness — Two Critical Limitations:
1. Polar solvents: Viton™'s fluorine-rich backbone provides exceptional resistance to non-polar hydrocarbons, but this same structure makes it vulnerable to polar solvents — particularly ketones (acetone, MEK), esters (ethyl acetate), THF, and certain amines. These molecules interact with the fluoropolymer chains, causing significant swelling and loss of mechanical properties.[1] Always verify compatibility with the Chemours Chemical Resistance Guide[1] before using Viton™ with any solvent. Also note that Viton™ performs poorly in phosphate ester fluids (Skydrol) and ammonia.
2. High-temperature limits: While rated to 400°F (204°C),[1] Viton™'s elastic recovery and compression set resistance begin to deteriorate above 350°F (177°C) in continuous service. Above this threshold, the material progressively hardens and loses the ability to conform to sealing surfaces — resulting in leakage even though the material has not chemically degraded. For continuous duty above 350°F, consider PTFE or consult U.S. Solid for high-temperature valve configurations. Cost is also higher than NBR or EPDM; Viton™ is a Chemours brand name[3] — generic FKM grades vary in fluorine content and performance.
- Virtually universal chemical compatibility — resistant to virtually all acids, alkalis, and solvents
- Widest temperature range of any seal material — the only choice for cryogenic or >450°F applications
- FDA-compliant for food, beverage, pharmaceutical, and semiconductor applications
- Zero outgassing — suitable for clean-room, vacuum, and high-purity water systems
Weakness — Cold Flow and Dynamic Sealing Limitations: PTFE has a critical mechanical limitation known as cold flow (creep) — under sustained compressive or clamp load, PTFE slowly deforms and extrudes into adjacent gaps, even at room temperature. In solenoid valves, this means: (1) in high-pressure static applications (>150 psi), the seat material may creep away from the sealing face over time, causing gradual internal leakage; (2) in high-cycle dynamic applications (rapid open/close switching), repeated compression cycles accelerate deformation. Valve manufacturers compensate for this through specific seat geometry, spring preload, and anti-extrusion designs — these valves are not interchangeable with standard elastomer-seat models. If you need PTFE for chemical reasons but face high pressure or high cycle rates, request valves with PTFE-specific seat designs from U.S. Solid. Premium cost is justified only where chemical inertness or extreme temperature range is genuinely required.
3. Chemical Compatibility Chart
Use this table to quickly compare how each seal material performs against common fluids. Selections marked A are recommended for continuous use.
| Fluid / Medium | NBR | EPDM | Viton™ | PTFE |
|---|---|---|---|---|
| Water (Cold, <120°F / 50°C) | A | A | A | A |
| Water (Hot, 120–180°F / 50–82°C) | B | A | B | A |
| Saturated Steam | D | A | C | A |
| Compressed Air & Inert Gases | A | A | A | A |
| Petroleum Oil / Hydraulic Fluid | A | D | A | A |
| Gasoline, Diesel, Kerosene | A | D | A | A |
| LPG / Propane / Butane | A | C | A | A |
| Natural Gas | A | B | A | A |
| Skydrol / Phosphate Ester Fluids | D | A | D | A |
| Sulfuric Acid (<10%) | C | B | A | A |
| Hydrochloric Acid | C | A | B | A |
| Sodium Hydroxide (Caustic) | B | A | C | A |
| Acetone / Ketones / Esters | C | A | D | A |
| Methanol / Ethanol (Alcohols) | A | A | B | A |
| Ethylene Glycol (Antifreeze) | A | A | B | A |
| Outdoor / UV / Ozone Exposure | C | A | A | A |
* Ratings are for general reference. Actual performance depends on concentration, temperature, pressure, and exposure duration. For critical or unusual applications, always test under your actual operating conditions. Data compiled from: Chemours Viton™ Chemical Resistance Guide[1] and ERIKS Rubber Chemical Resistance Guide.[2]
4. Common Application Scenarios
Not sure which seal material you need? Match your application to one of these common scenarios.
Hydraulic Systems & Lubrication Lines
Petroleum-based or synthetic hydraulic oils, lubricating greases, and machine tool coolant lines. Found in industrial presses, injection molders, and automated equipment.
Recommended: NBR (standard) or Viton™ (high-temp >250°F)Fuel Dispensing & Petroleum Handling
Gasoline, diesel, kerosene, ethanol blends (E10, E15), and biodiesel. Common in fueling equipment, backup generators, and mobile fuel systems.
Recommended: Viton™ (preferred) or NBRHot Water & Heating Systems
Hot water circulation, boiler feed lines, radiant floor heating, and industrial process water. Applications in HVAC, water heaters, and food processing.
Recommended: EPDM (for temps >180°F) or PTFESteam & High-Temperature Processes
Saturated steam, superheated water, and thermal oil lines. Found in steam sterilizers, food processing, industrial laundry, and steam tracing systems.
Recommended: EPDM or PTFE — NBR and Viton™ are NOT suitableChemical Processing & Corrosive Media
Acids, alkalis, solvents, and aggressive chemicals in manufacturing, water treatment, and chemical dosing systems.
Recommended: PTFE (broadest compatibility) or Viton™Outdoor & Weather-Exposed Installations
Irrigation automation, mobile equipment, rooftop HVAC, environmental monitoring stations. Exposed to sunlight, rain, temperature swings, and ozone.
Recommended: EPDM (best UV/ozone resistance) or Viton™Food, Beverage & Potable Water
Water dispensers, brewing systems, food processing lines, medical device cooling. Requires FDA-compliant materials with no leaching or odor.
Recommended: EPDM (certified) or PTFECryogenic & Extreme Cold Applications
Liquid nitrogen, LNG transfer, refrigerated gas lines, and cold box isolation. Operating temperatures below -40°F (-40°C).
Recommended: PTFE (rated to -328°F) — elastomers become brittle5. Quick Decision Guide
Answer these questions to narrow down your seal material in seconds:
Flowchart: Find Your Seal Material
6. U.S. Solid Solenoid Valves by Seal Material
U.S. Solid stocks a complete range of solenoid valves configured with the seal material that matches your application. Browse by seal type or tell us your requirements — we'll help you find the right valve.
General Purpose Solenoid Valves
For water, air, and petroleum oils. Brass or stainless steel body. 1/8" to 2" ports.
NBR SealsSteam & Hot Water Valves
Rated for saturated steam to 300°F. Essential for sterilizers, boilers, and process heating.
EPDM SealsCorrosion-Resistant Valves
Brass body with Viton™ seals for fuels, chemicals, and high-temperature oil applications.
Viton™ SealsProcess & Specialty Valves
PTFE seats for the most aggressive media. Food, pharma, chemical, and high-purity systems.
PTFE Seals7. Frequently Asked Questions
Q: Can I use NBR seals with ethanol blends like E10 or E15?
A: Yes, NBR performs well with ethanol blends up to about 15% ethanol content. For higher ethanol concentrations (E85, E100) or specific biofuel formulations, testing is recommended as performance can vary with additive packages.
Q: Why does EPDM fail when it contacts petroleum oil?
A: EPDM has a hydrocarbon-based polymer backbone that is chemically attracted to petroleum oils. This causes the material to swell dramatically and lose mechanical integrity. This is a fundamental chemical incompatibility — always use NBR or Viton™ in oil service.
Q: Is Viton™ worth the extra cost over NBR?
A: For applications requiring chemical resistance beyond standard petroleum oils, or operating above 250°F, Viton™ provides significantly better long-term performance and reduced maintenance costs. For standard oil service at room temperature, NBR offers the best value.
Q: What's the difference between Viton™ A, B, and F types?
A: Viton™ A, B, and F denote different fluoroelastomer grades with varying fluorine content (65–70%).[1][3] Higher fluorine content improves chemical resistance but affects low-temperature flexibility. U.S. Solid valves use standard Viton™ A-type seals suitable for most industrial applications.
Q: How do I know if a PTFE valve is truly food-grade?
A: Look for FDA compliance certification. PTFE itself is chemically inert and food-safe, but the entire valve construction — body, spring, and all wetted components — must meet food-contact regulations. U.S. Solid offers valves specifically designed for food and beverage applications.
Get the Right Valve — First Time
Tell us your fluid type, operating temperature, and pressure. Our technical team will recommend the exact valve and seal material combination for your application.
References
- Chemours Company. Viton™ Fluoroelastomers Chemical Resistance Guide. Chemours Performance Solutions. Available at: https://chemours-util.my.salesforce-sites.com/CRG_VitonGuide. Accessed April 2026.
- ERIKS. Rubber Chemical Resistance Guide. ERIKS Industrial Services. Available at: https://eriks.co.uk/en/tools/rubber-chemical-resistance-guide/. Accessed April 2026.
- Chemours Company. Viton™ Fluoroelastomer Products — Brand Overview. Available at: https://www.viton.com/en/products. Accessed April 2026.
- U.S. Solid. How to Properly Wire Your Solenoid Valve — A Step-by-Step Guide. U.S. Solid Blog. Available at: https://ussolid.com/blogs/solenoid-valve/how-to-properly-wire-your-solenoid-valve-a-step-by-step-guide. Accessed April 2026.
- U.S. Solid. Solenoid Valve Blog — Technical Guides & Application Articles. U.S. Solid Blog. Available at: https://ussolid.com/blogs/solenoid-valve. Accessed April 2026.