Product Advantages
1. Material Composition & Sealing Mechanism
High-temperature FKM O-rings are molded from FKM compounded with heat-resistant reinforcing fillers, peroxide curing agents, and thermal stabilizers, then compression-molded and vulcanized into toroidal elastomers with circular cross-section. When compressed in a gland, contact stress is generated; sealing is established when contact stress exceeds the internal pressure of the medium. High-temperature formulations optimize crosslink density and thermal stabilizer systems to suppress main-chain scission and crosslink degradation, delaying hardening and compression set accumulation.
2. High-Temperature Performance
Standard FKM grades operate continuously at -45°C to 200°C (ASTM D2000). Special high-temperature grades reach 225°C continuous, with intermittent peaks of 250°C–300°C (cumulative ≤48 hours). After 200°C×70h hot air aging, tensile strength retention ≥80%, elongation retention ≥70%.
3. High-Temperature Media Compatibility
Suitable for mineral-based lubricating oils, hydraulic oils, engine oils, gear oils, diesel, gasoline, and air at elevated temperatures. No hardening, embrittlement, or excessive swell in 200°C oil baths. Resists strong acids, strong bases, ammonia water, high-temperature steam, and mixed solvents. High-temperature grades also resist thermal oxidation, ozone, and UV aging.
4. Low Compression Set at High Temperatures
Standard hardness: Shore A 75±5 (75+ recommended for high-temperature grades). Compression set (200°C×70h, 25% compression) ≤30% (ASTM D395). At 275°C×70h, compression set ≤50%. Ensures sealing contact pressure is maintained through repeated thermal cycling (heat → cool → reheat).
5. Full Size Range & Customization Available
Cross-section 1.0–7.0mm, OD 10–450mm. Complies with GB/T 3452.1 and AS568. Sample-based customization available without drawings – mold development 3–5 days.
Product Specifications
| Parameter | Specification |
|---|---|
| Material | FKM (Fluorocarbon) – High-Temperature Grade |
| Hardness (Shore A) | 75±5 (75+ recommended; custom 70–90 available) |
| Standard Continuous Temp. | -45°C ~ +200°C |
| High-Temp Grade Continuous | Up to +225°C |
| Intermittent Peak Temp. | 250°C ~ 300°C |
| Recommended Compression Ratio | Static axial: 15%–30%; Static radial: 20%–35%; Dynamic: 10%–20% |
| Max Working Pressure | Without backup ring ≤10MPa; with backup ring ≥30MPa |
| Outer Diameter Range | 10mm ~ 450mm |
| Cross-section Range | 1.0mm ~ 7.0mm |
| Color | Black (standard), brown/green optional |
| Compression Set (200°C×70h) | ≤30% (ASTM D395) |
| Compression Set (275°C×70h) | ≤50% |
| Tensile Strength | ≥16 MPa |
| Elongation at Break | ≥150% |
| Hot Air Aging (200°C×70h) | Tensile retention ≥80%; Elongation retention ≥70% |
| Standard | GB/T 3452.1 / AS568 / ISO 3601 / custom drawing |
| Flash Trim | 45° split, trim precision ≤0.1mm |
| Surface Quality | Smooth finish, no bubbles, cracks, or impurities |
Installation & Operation Procedure
1. Pre-installation Inspection & Cleaning
Clean the gland and mating surfaces with lint-free cloth soaked in acetone or alcohol to remove chips, oil films, and old seal residue. Inspect gland bottom and walls for scratches, pits, or burrs. Minor defects are more likely to cause premature seal failure at high temperatures.
2. Lubrication
Apply a thin, uniform layer of high-temperature lubricant compatible with the system media (fluorinated grease or high-temp hydraulic oil) on the O-ring surface to reduce installation friction and prevent surface damage.
3. Installation Procedure
Use the spiral insertion method or a tapered installation sleeve to gradually push the O-ring into the gland. Never use sharp tools. Ensure the O-ring is not twisted in the gland. Stretch the O-ring OD by no more than 2% of its original circumference to avoid permanent cross-section deformation.
4. Compression Ratio Verification
Measure gland depth and O-ring cross-section height post-installation to calculate actual compression. Static seals: 15%–30% (axial) or 20%–35% (radial); dynamic seals: 10%–20%. At high temperatures, too low compression results in insufficient sealing pressure after thermal expansion.
5. High Pressure + High Temperature Combinations
For system pressures >10MPa, install a backup ring (PTFE or PEEK) on the pressure side and strictly control extrusion gap to prevent the O-ring from being extruded at elevated temperatures.
Frequently Asked Questions
Q1: What is the difference between high-temperature FKM and standard FKM?
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High-temperature FKM uses peroxide curing (Bisphenol AF + BPP) with higher crosslink density and more thermal stabilizers. Standard FKM hardens rapidly above 200°C with sharp compression set increase; high-temperature grades maintain elasticity at 225°C continuous, with compression set ≤50% at 275°C×70h. The overall service temperature range for FKM is -45°C to 300°C.
Q2: What is the failure threshold for high-temperature FKM under continuous high-temperature service?
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The primary failure mode is compression set exceeding 25% of original cross-section height. When temperature exceeds the grade limit (standard grade >200°C, high-temperature grade >225°C continuous, or >275°C cumulative beyond 48 hours), the crosslink network degrades, causing rebound loss, contact stress decay, and eventual leakage.
Q3: What peak temperatures can high-temperature FKM withstand?
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Standard grades: 250°C intermittent (cumulative ≤8 hours). High-temperature grades : 275°C intermittent (cumulative ≤48 hours). FKM can reach up to 300°C maximum. Beyond peak temperature or cumulative time, irreversible thermal degradation occurs, causing seal failure.
Q4: What information is required for a custom quote?
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Provide: dimensions (cross-section, inner diameter, or outer diameter), temperature grade (standard 200°C / high-temp 225°C / ultra-high 250°C+), Shore A hardness (75 recommended), maximum continuous temperature, peak temperature and duration, contact media, and system pressure.
