Complete Materials Guide

NBR (Nitrile) and FKM (Viton) are both excellent for oil and fuel resistance, but they differ significantly in temperature rating and chemical resistance breadth. NBR is cost-effective and handles petroleum oils well up to 120°C. FKM operates up to 200°C, resists a far wider range of aggressive chemicals including concentrated solvents, and has superior long-term performance — but at a significantly higher material cost. For standard hydraulic and fuel applications, NBR is the default choice. FKM is specified when temperature exceeds 120°C, chemical exposure is severe, or seal life in aggressive media is critical.

It depends on how extreme the temperature requirement is. For up to 150°C, EPDM or HNBR are good choices. For 150–200°C, FKM (Viton) is the standard specification. For 200–230°C, high-consistency silicone (VMQ) or specialty FKM compounds are used. Beyond 230°C and up to 325°C, FFKM (Perfluoroelastomer — Kalrez/Chemraz) is the only elastomeric option. Always consider the media being sealed alongside temperature — a material must resist both. Contact Harkesh engineering to specify the right compound for your exact operating conditions.

Yes. Harkesh Rubber has in-house compounding capability since inception. Our technical team formulates custom elastomer compounds by selecting the base polymer and optimizing the filler system, plasticizer package, and vulcanizing system to meet specific performance targets — whether that means a particular hardness, compression set, chemical resistance profile, or low-temperature flexibility. Development timelines typically run 4–8 weeks from specification to first production samples. Custom compounding is available for all major base polymers: NBR, FKM, EPDM, HNBR, CR, IIR, and VMQ.

Yes. Harkesh provides material samples and standard test specimens on request for qualified projects. For O-rings and standard profiles in our stocked materials, we can typically dispatch samples within 3–5 working days. For custom compounds or non-standard profiles, sample lead times depend on the complexity of the specification. Please use the Contact Engineering form or reach out to our sales team with your application details, required material, and profile dimensions to initiate a sample request.

Silicone (VMQ) is the most widely used material for food and pharmaceutical contact sealing. We supply FDA-compliant and food-grade silicone compounds that meet FDA 21 CFR 177.2600 requirements. For more demanding pharmaceutical or biotech applications requiring higher chemical resistance, FKM in FDA grades is also available. EPDM is used in water and steam systems in food processing. For the most stringent pharmaceutical applications (e.g., aggressive solvent systems), FFKM compounds are available. All food and pharma grade compounds are supplied with full compound documentation.

FFKM stands for Perfluoroelastomer — it is the highest-performance elastomeric sealing material available. Unlike FKM (which has some fluorine content), FFKM is fully fluorinated, giving it near-universal chemical resistance comparable to PTFE, while retaining the elastic compression set recovery of an elastomer. It operates from -10°C to +325°C. FFKM is specified for semiconductor fabrication equipment (where contamination from swollen seals is unacceptable), aggressive chemical processing plants, pharmaceutical reactors with harsh solvents, and any application combining extreme temperature with aggressive chemical attack. The trade-off is cost — FFKM seals can be 20–100x the price of equivalent NBR seals. Trade names include Kalrez (DuPont/DowDuPont) and Chemraz (Greene Tweed).