PTFE O-Ring
Discover Kaxite Sealing's PTFE O-Ring, a high-performance sealing solution crafted from premium PTFE for unmatched chemical resistance, durability, and temperature tolerance. Ideal for engineers and industries like automotive and aerospace, it ensures leak-free performance in demanding applications, offering reliability and peace of mind. Its superior design outperforms standard seals, minimizing maintenance and downtime. Experience confidence in every application with Kaxite Sealing's cutting-edge technology.
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Product Description
Compound O-Ring: Multi-Material Sealing Solutions by Kaxite Sealing
Kaxite Sealing's Compound O-Ring is a high-performance sealing component engineered for applications that require the combined properties of two or more elastomeric materials in a single sealing element. Unlike standard single-material O-rings, compound O-rings are produced by bonding or co-molding different rubber compounds—such as EPDM, NBR, Silicone, FKM (Viton), or HNBR—into one integrated seal. This design allows engineers to balance conflicting requirements like chemical resistance versus high-temperature stability, or elasticity versus pressure resistance.
Also known as multi-material O-rings or dual-durometer O-rings, this product family is widely used alongside our rubber O-rings, PTFE O-rings, rubber gaskets and custom molded sealing components.
For over two decades, Kaxite Sealing has supplied compound O-rings to chemical processing, oil & gas, food & beverage, pharmaceutical, and water treatment industries worldwide. Each compound grade is rigorously tested for hardness, tensile strength, compression set, and aging resistance to ensure reliable long-term sealing performance. We can also produce non-standard compound O-rings according to customer drawings, groove dimensions, or application parameters.
What Is a Compound O-Ring and Why Choose It?
A compound O-ring combines two or more elastomeric materials into one sealing element, either through co-molding, bonding, or dual-durometer construction. This approach is chosen when a single material cannot meet all application requirements. Common reasons to select a compound O-ring include:
- Chemical + Thermal Balance: The inner layer resists aggressive chemicals, while the outer layer withstands high temperatures.
- Low-Temperature Flexibility + High-Temperature Stability: One compound maintains elasticity in cryogenic conditions, the other resists hardening at elevated temperatures.
- Enhanced Sealing Force: A softer outer layer conforms to surface irregularities, while a harder core resists extrusion under pressure.
- Extended Service Life: Multi-material construction reduces compression set and aging, extending replacement intervals.
- Cost Optimization: Expensive high-performance material is used only where needed, reducing overall unit cost.
[ Main Properties ]
We can produce other non-nominal compound O-rings. The table below summarizes the mechanical and thermal properties of three standard compound O-ring grades (A, B, C), each optimized for different application requirements.
| Property | Unit | Compound Grade | |||
|---|---|---|---|---|---|
| A | B | C | |||
| Normal Conditions | Hardness | Shore A (JIS K 6253) | 70-90 | 70-90 | 60-75 |
| Elongation, min | % | 60 | 60 | 80 | |
| Tensile Strength, min | MPa | 16 | 16 | 16 | |
| Compressibility | % | 50-60 | 50-60 | 60-75 | |
| Recovery | % | >85 | >85 | >70 | |
| Permanent Set | % | <10 | <10 | <20 | |
| 230°C × 24h Hot Air Aging | Change of Hardness, max. | Shore A | -5 ~ +5 | -5 ~ +5 | -5 ~ +5 |
| Change of Tensile Strength, max. | % | -15 | -15 | -15 | |
| Change of Elongation, max. | % | -20 | -20 | -20 | |
| Compression Permanent Set | 175°C × 70h | % | ≤20 | ≤20 | ≤30 |
| Color | — | Brown | Black | Red | |
| Applications | Temperature Limits | °C | -20 ~ 250 | -20 ~ 200 | -50 ~ 200 |
| Pressure Limits | MPa | 0 ~ 35 | |||
| Strong caustics, moderate acids, chlorine, gases, water, steam, hydrocarbons, hydrogen and aluminum fluoride — except elemental fluorine and molten sodium. | |||||
Grade Selection Guide: A vs. B vs. C
Choosing the right compound grade depends on your operating temperature, chemical exposure, and pressure requirements. Use the guide below to match the grade to your application.
| Requirement | Recommended Grade | Reason |
|---|---|---|
| High-temperature steam or chemical service (up to 250°C) | A (Brown) | Highest temperature limit; lowest permanent set (<10%) |
| General industrial sealing with balanced properties | B (Black) | Good chemical resistance and mechanical strength |
| Low-temperature applications (down to -50°C) | C (Red) | Highest elongation (80%) and lowest hardness (60-75 Shore A) |
| High-pressure systems (up to 35 MPa) | All grades | All three grades share the same pressure limit |
| Strong caustics, moderate acids, chlorine service | All grades | All grades offer the same chemical resistance profile |
Selection Tip: If your application involves both high temperature (above 200°C) and chemical exposure, Grade A is the safest choice. If your system operates in cold climates or cryogenic conditions, Grade C provides the best flexibility. For general-purpose sealing where no extreme condition dominates, Grade B offers the most balanced performance at a competitive cost.
Typical Applications by Industry
Compound O-rings are used across a wide range of industries where single-material seals cannot meet combined performance requirements.
Chemical Processing
Sealing pumps, valves, reactors, and flange connections exposed to aggressive acids, caustics, and solvents.
Oil & Gas
Wellhead equipment, pipelines, and refinery fittings requiring resistance to hydrocarbons and hydrogen sulfide.
Food & Beverage
Sanitary fittings, filling machines, and CIP systems needing FDA-compliant, non-toxic sealing materials.
Pharmaceutical
Sterile process equipment, reactors, and filtration systems requiring USP Class VI compliance.
Water Treatment
Pumps, valves, and distribution systems requiring long-term resistance to chlorine and ozone.
Power Generation
Steam turbines, heat exchangers, and boiler systems operating at high temperature and pressure.
[ Specifications ]
Kaxite Sealing offers a full range of compound O-ring cross-sections and inside diameters to fit standard and custom grooves. All dimensions are manufactured to ISO 3601 and AS568 tolerances unless otherwise specified.
| Section Diameter (mm) | Nominal Inside Diameter (mm) | Section Diameter (mm) | Nominal Inside Diameter (mm) |
|---|---|---|---|
| 1.80 ± 0.10 | 20 ± 0.10 ~ 300 ± 1.60 | 6.00 ± 0.13 | 80 ± 0.80 ~ 400 ± 2.00 |
| 2.60 ± 0.10 | 20 ± 0.15 ~ 300 ± 1.60 | 6.30 ± 0.14 | 80 ± 0.80 ~ 400 ± 2.00 |
| 3.55 ± 0.10 | 25 ± 0.15 ~ 300 ± 1.60 | 7.00 ± 0.14 | 100 ± 0.65 ~ 1000 ± 4.00 |
| 4.00 ± 0.10 | 40 ± 0.20 ~ 300 ± 1.60 | 8.00 ± 0.16 | 110 ± 1.00 ~ 2000 ± 4.00 |
| 4.60 ± 0.10 | 40 ± 0.20 ~ 300 ± 1.60 | 10.00 ± 0.18 | 200 ± 1.50 ~ 2000 ± 6.00 |
| 5.00 ± 0.10 | 40 ± 0.25 ~ 400 ± 1.80 | 12.00 ± 0.18 | ≥400 ± 1.50 ~ 2000 ± 6.00 |
| 5.30 ± 0.13 | 60 ± 0.30 ~ 400 ± 1.80 | 14.00 ± 0.18 | ≥400 ± 1.50 ~ 2000 ± 6.00 |
| 5.50 ± 0.13 | 60 ± 0.30 ~ 400 ± 1.80 | 16.00 ± 0.18 | ≥400 ± 1.50 ~ 2000 ± 6.00 |
| 5.70 ± 0.13 | 60 ± 0.30 ~ 400 ± 2.00 | — | — |
Custom Orders: Non-standard section diameters and inside diameters are available. Please provide groove dimensions or application parameters, and our engineering team will recommend the optimal compound and size. See our full range of rubber O-rings, PTFE O-rings and rubber gaskets for related sealing solutions.
Ordering Information & Quality Assurance
To help you plan your procurement, the following information applies to all standard and custom compound O-ring orders.
- Standards: Manufactured to ISO 3601 and AS568 tolerances. FDA 21 CFR 177.2600 and USP Class VI grades available on request.
- MOQ: 100 pieces per size for standard grades; 500 pieces per size for custom compounds.
- Lead Time: 7-15 days for standard sizes; 15-25 days for custom sizes and compounds.
- Packing: Individually bagged or bulk packed in cartons, with size and grade labels. Custom packing available.
- Quality: Batch traceability, dimensional inspection and material certificates available.
Installation and Usage Recommendations
To ensure optimal sealing performance and service life, follow these installation guidelines:
- Inspect the groove: Ensure the groove is clean, free of scratches, and meets the recommended surface finish (typically 0.8-1.6 µm Ra for dynamic seals, 1.6-3.2 µm for static seals).
- Lubricate properly: Apply a compatible lubricant (silicone grease for silicone O-rings, PTFE grease for EPDM/FKM) to reduce installation friction and prevent twisting.
- Avoid over-stretching: Do not stretch the O-ring more than 5% during installation; excessive stretching reduces cross-section and sealing force.
- Check compression ratio: For static seals, the recommended compression ratio is 15-25%. For dynamic seals, 10-15%. Verify groove depth matches O-ring cross-section.
- Verify chemical compatibility: Confirm the compound grade is compatible with all media it will contact, including cleaning agents and lubricants.
- Replace after disassembly: O-rings should not be reused after removal, as they undergo permanent deformation during service.
Frequently Asked Questions
Q: What is the difference between a compound O-ring and a standard O-ring?
A standard O-ring is made from a single elastomeric material. A compound O-ring combines two or more materials—either through co-molding, bonding, or dual-durometer construction—to achieve properties that no single material can provide. For example, a compound O-ring may have a chemical-resistant inner layer and a heat-resistant outer layer, making it suitable for applications where both chemical exposure and high temperature are present.
Q: How do I choose between Grade A, B, and C?
Grade A (Brown) is recommended for high-temperature service up to 250°C and applications requiring low permanent set. Grade B (Black) is the general-purpose grade for balanced chemical and mechanical performance. Grade C (Red) is best for low-temperature applications down to -50°C, thanks to its higher elongation and lower hardness. If your application involves both extreme high and low temperatures, contact our engineering team for a custom compound recommendation.
Q: Can compound O-rings be used in food and pharmaceutical applications?
Yes, provided the correct compound grade is selected. For food contact, we recommend grades that comply with FDA 21 CFR 177.2600. For pharmaceutical applications, USP Class VI compliant grades are available. Please specify your regulatory requirements when ordering, and we will supply the appropriate certification.
Q: What is the maximum pressure a compound O-ring can handle?
All three standard grades (A, B, C) are rated for pressures up to 35 MPa (approximately 5,000 psi) in static sealing applications. For higher pressures, a back-up ring or a different sealing design (such as a Kammprofile gasket or spiral wound gasket) may be required. Contact our engineers for high-pressure recommendations.
Q: Do you offer custom sizes and non-standard compounds?
Yes. We can produce compound O-rings in non-standard section diameters, inside diameters, and material combinations. Send us your drawing, groove dimensions, or application parameters (temperature, pressure, media), and our engineering team will recommend the optimal compound and size. Lead time for custom orders is typically 15-25 days depending on complexity.
Ready to Optimize Your Sealing Performance?
Get a free consultation and quote for your Compound O-Ring requirements. Our engineers will help you select the right grade, size, and material combination for your specific application.
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