How to Select NBR, EPDM, FKM and Silicone Rubber by Media and Temperature

How to Select NBR, EPDM, FKM and Silicone Rubber by Media and Temperature

This guide supports preliminary material selection for custom seals, gaskets, hose linings, protective boots and molded rubber parts. A polymer name is only a starting point. The final choice must be checked against the actual medium, concentration, temperature profile, pressure, movement, compression, tolerances and sample-test requirements.

1. Direct answer: temperature alone is not enough

Start with the medium, then confirm continuous temperature, short peaks, pressure, movement and sealing geometry. NBR is often reviewed for mineral oils and fuel-related applications; EPDM is commonly considered for water, hot water, steam and weather exposure; FKM is considered where higher heat, oil or chemical resistance is needed; silicone is considered for wide temperature exposure, clean contact or soft sealing. None of these statements is an automatic product guarantee.

2. Scope and limits

The framework applies to static seals, reciprocating seals, rotary seals, hose linings, equipment boots and general industrial rubber parts. It is not a substitute for food-contact, potable-water, medical, hazardous-chemical or explosion-protection approvals. If the medium, concentration, temperature or pressure is unknown, the material should remain in preliminary-review status.

3. Initial comparison

4. Define the medium precisely

“Oil”, “chemical” or “cleaning liquid” is not enough for a reliable decision. Additives, concentration and temperature can change swelling, hardening and permeation. Record the supplier grade or safety data sheet where possible.

5. Confirm temperature and exposure time

Record continuous temperature, short peaks, ramp rate and dwell time. A single generic temperature number cannot replace a compound data sheet. Static compression, dynamic friction, steam and pressurized media can produce different limits. Mark the final temperature range as “to be confirmed against compound and test data” until evidence is available.

6. Pressure, movement and geometry

A flange gasket, reciprocating seal, rotary seal and hose lining have different requirements. At higher pressure, check extrusion clearance, backup rings, hardness and surface finish. For dynamic service, confirm speed, frequency, lubrication and heat dissipation. A compatible polymer does not guarantee a reliable finished part if the cross-section, tolerance or installation is wrong.

7. Dimensions, tolerances and hardness

Without a drawing, an old-part photo, measured dimensions and installation position can support an initial discussion. They cannot prove interchangeability because old parts may already be swollen, permanently deformed or worn.

8. Verification by project stage

After the first material screen, test the most uncertain or hazardous condition. Static seals may require compression-set and leakage checks. Dynamic seals require friction, wear, temperature and trend monitoring. Chemical service may require immersion, mass/volume change and visual inspection. Hose projects also require reinforcement, coupling and pressure-test review.

9. Failure symptoms and investigation

10. Installation, storage and acceptance

Before installation, inspect the groove, lead-in chamfers, burrs, cleanliness and lubricant. Avoid twisting, stretching beyond the installation allowance and cutting on sharp edges. Store parts away from sunlight, ozone, heat, oil contamination and heavy compression. The exact storage period and packaging should follow the compound and project requirements. Acceptance records should include compound lot, dimensions, hardness, appearance, quantity, drawing revision and deviations.

11. RFQ information checklist

• • Medium name, concentration, supplier grade or safety data sheet;
• • Continuous and peak temperature, pressure and pressure pulses;
• • Static or dynamic duty, speed, frequency and lubrication;
• • Cross-section, groove drawing, old-part photos and key dimensions;
• • Material, hardness, tolerances, colour and surface requirements;
• • Quantity, sample requirement, packaging, destination and project stage;
• • Required tests, regulations, lot traceability or acceptance records.

12. FAQ

Can NBR, EPDM and FKM replace one another?

Not directly. Recheck medium, temperature, pressure, compression, movement and regulatory requirements, then validate the drawing and sample.

Can temperature alone determine the material?

No. Medium, pressure, exposure time, movement and geometry are equally important.

Is EPDM suitable for every oil?

No. Oil formulation and additives differ. Use the specific medium information and compatibility evidence.

Is FKM always better than NBR?

No. FKM may be preferable for some heat or oil conditions, but low-temperature flexibility, dynamic wear, cost and chemical compatibility still require review.

Is silicone suitable for high-pressure dynamic sealing?

It cannot be confirmed from the polymer name. Check tear strength, friction, compression set, surface and geometry.

Can I request a quotation without a drawing?

An initial discussion is possible with photos, measured dimensions, installation position, medium and quantity. Formal quotation still requires the critical dimensions and service conditions.

Why does the same polymer last differently in different equipment?

Temperature cycling, pressure, friction, surface finish, compression and exposure time differ. The polymer name alone does not define finished-part life.

Can a general-purpose sample be used as the final part?

It may support assembly and appearance review. For high-risk media or temperatures, representative-condition testing is needed before final approval.

What test records should be requested?

Typical records include compound lot, dimensions, hardness, appearance, immersion or pressure testing. The exact set follows the drawing, standard and customer acceptance plan.

13. Evidence and technical communication boundary

This page provides a material-screening and RFQ framework. It does not replace supplier data sheets, third-party testing, regulatory review or engineering approval. Specific compound limits, temperature ranges, life, certification and compatibility conclusions must be supported by drawings, data sheets, sample tests and project requirements. Customers can submit details through the materials database, custom seal product pages, industrial hose pages or the contact page.

14. A practical decision sequence for engineers and buyers

Use the following sequence before asking for a final quotation. First, write the actual medium and identify whether contact is continuous, intermittent, splash-only or part of a cleaning cycle. Second, record the normal temperature and the highest credible short-term temperature, rather than relying on an assumed operating range. Third, document pressure, vacuum, pulsation and any pressure spikes. Fourth, identify whether the part is static, reciprocating, rotary or subject to installation movement. Fifth, check the groove, clearance, compression and surface finish. Only after these inputs are available should NBR, EPDM, FKM, silicone or another compound be compared.

This sequence prevents a common procurement error: choosing a polymer from a catalogue keyword and discovering later that the seal geometry, cleaning procedure or pressure peak is the actual failure driver. If one of the five input groups is unknown, the quotation should be marked as preliminary and the missing information should be listed in the inquiry record.

15. How to compare supplier recommendations

Supplier recommendations should be compared on the same evidence basis. Ask whether the recommendation refers to a standard compound, a special formulation or a finished part with a specific hardness and post-cure process. Confirm whether the stated compatibility is based on a data table, immersion test, field record or engineering judgement. These evidence types are not equivalent. A general polymer chart may support an initial screen, while a project with concentrated chemicals, high pressure or repeated temperature cycling may require a sample or laboratory test.

16. When a sample test is the responsible next step

A sample test is particularly important when the medium is concentrated, the temperature is close to a material limit, the seal is safety-critical, the part is difficult to replace, or the failure consequence is high. The test should use the proposed compound, hardness and geometry whenever practical. Record the exposure medium, concentration, temperature, duration, pressure, movement and inspection method. Useful observations may include mass or volume change, hardness change, cracks, tackiness, surface blistering, leakage and dimensional recovery. A pass or fail statement without test conditions is not sufficient evidence for a production decision.

17. Communication checklist for a traceable quotation

The quotation package should distinguish confirmed facts from assumptions. Confirmed facts may include the customer drawing, measured dimensions, stated medium and requested quantity. Assumptions should be labelled, for example “temperature supplied by customer” or “dynamic duty not yet confirmed.” Open questions should be assigned to a person and a date. The final recommendation should state which data supports the material choice and which conditions still require validation. This makes later engineering review, repeat ordering and failure analysis much more reliable.

18. Yuhang Rubber technical support

南京宇航橡胶（Nanjing Yuhang Rubber） provides industrial rubber products and technical communication for material selection, seals and hoses. Use the materials database, custom seal material selection, industrial rubber hoses and contact page to submit drawings, medium data and service conditions.