FKM Fluorocarbon O-Ring Guide
FKM Fluorocarbon O-Ring Guide
FKM (fluorocarbon) elastomers are the go-to choice for aggressive chemicals, high temperatures, and vacuum service. This guide summarises property data, grade selection, and validation tests for critical sealing applications.
## Property Snapshot
| Property | Typical Value | Notes |
| — | — | — |
| Temperature range | -20 °C to +200 °C | Specialty low-temperature grades reach -40 °C |
| Chemical resistance | Aromatic fuels, acids, solvents, oxidisers | Avoid hot amines unless using specialty grades |
| Hardness | 55–95 Shore A | 75–90A common for industrial service |
| Compression set | ≤25 % @ 200 °C (post-cured) | Post-cure essential |
| Permeation | Low | Preferred for vacuum and fuel vapor containment |
## Grade Selection
– **General purpose (Type A)** – automotive fuels, lubricants.
– **Improved chemical (Type B)** – better base resistance, low compression set.
– **Specialty (Type F, GF, GFLT)** – amine-resistant, low-temperature, peroxide-resistant blends.
– **Filled grades** – carbon/graphite/PTFE filled for dynamic wear reduction.
## Application Guidance
– **Chemical processing** – pump seals, valve seats, instrumentation.
– **Automotive & aerospace** – fuel system components, turbocharger seals.
– **Oil & gas** – downhole equipment, sour gas service (with proper grade).
– **Semiconductor** – use ultra-clean grades; verify outgassing specs.
## Design Tips
– Keep static compression 15–25 %; dynamic 10–15 %.
– Use backup rings when gaps >0.25 mm or pressures >10 MPa.
– For dynamic applications, select filled compounds to control friction/heat.
– Ensure hardware surfaces are polished (Ra ≤ 0.4 µm) to prevent abrasion.
– Always post-cure molded parts to remove residual volatiles (typically 230 °C, 24 h).
## Testing Checklist
– Immersion in target media at operating temperature (ASTM D471).
– Compression set and stress relaxation for long-term sealing (ASTM D395).
– Sour-gas/amine resistance (NACE TM0187) if required.
– Low-temperature TR-10 and brittleness for GLT/GFLT grades.
– Vacuum outgassing (ASTM E595) for high vacuum/space applications.
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