For over two decades, Kaxite Seals has been at the forefront of sealing technology, specializing in high-performance fluoropolymer solutions. Among our core products, PTFE Gaskets stand out for their unparalleled chemical resistance and reliability in the most demanding environments. This guide provides a detailed technical overview, specifications, and application insights for our industry-leading PTFE gasket products.
Polytetrafluoroethylene (PTFE) gaskets are sealing components made from a synthetic fluoropolymer renowned for its exceptional properties. PTFE is inert to nearly all industrial chemicals and solvents, offers an extremely wide service temperature range, and provides excellent anti-stick and low-friction characteristics. These gaskets are engineered to create a secure, leak-proof seal between two mating flanges or surfaces, accommodating imperfections and preventing the escape or ingress of fluids and gases.
At Kaxite Seals, we manufacture PTFE gaskets from 100% virgin PTFE resins or compounded materials, ensuring consistent quality, purity, and performance tailored for specific industrial challenges, from pharmaceutical processing to aggressive chemical handling.
Kaxite Seals offers a comprehensive range of PTFE gasket types. Below are the technical specifications for our standard virgin PTFE sheet gaskets.
| Property | Test Method | Typical Value | Units |
|---|---|---|---|
| Specific Gravity | ASTM D792 | 2.14 - 2.20 | g/cm³ |
| Tensile Strength | ASTM D638 | 25 - 35 | MPa (psi) |
| Elongation at Break | ASTM D638 | 300 - 500 | % |
| Compression Set (22 hrs @ 25°C) | ASTM D395 Method B | 40 - 60 | % |
| Coefficient of Linear Thermal Expansion | ASTM D696 | 12 x 10-5 | cm/cm/°C |
| Thermal Conductivity | ASTM C177 | 0.25 | W/m·K |
| Volume Resistivity | ASTM D257 | >1018 | Ω·cm |
| Dielectric Strength | ASTM D149 | >60 | kV/mm |
| Limiting PV Value | - | 10,000 | psi·fpm |
| Gasket Type | Standard Forms | Available Thickness (Sheet) | Standard Color | Common Standards |
|---|---|---|---|---|
| Virgin PTFE Gaskets | Sheets, Rolls, Cut Gaskets (Full Face, Ring), Skived Tape | 0.5mm to 10mm (0.02" to 0.39") | White (Opaque) | ASME B16.21, DIN, ISO, Customer Print |
| Filled PTFE Gaskets | Sheets, Cut Gaskets | 1.5mm to 6mm (0.06" to 0.24") | Gray, Brown, Black (depending on filler) | ASME B16.21, DIN 3754, Custom |
| Expanded PTFE (ePTFE) Gaskets | Sheets, Tapes, Cord, Die-Cut Parts | 0.5mm to 3mm (0.02" to 0.12") | White | TA-Luft, FDA, USP Class VI |
| PTFE Envelope Gaskets | Jacketed Gaskets (with filler like rubber or graphite) | As per envelope core | White Jacket | ASME B16.20, B16.21 |
Q: What are the main limitations of PTFE gaskets?
A: While exceptional in chemical resistance, pure PTFE has a relatively high creep (cold flow) tendency under sustained load, which can lead to stress relaxation and potential leakage if not properly designed for. It is also not recommended for applications with molten alkali metals or certain fluorine compounds at high temperature and pressure. For high-stress applications, Kaxite Seals recommends filled PTFE or modified grades with improved creep resistance.
Q: Can PTFE gaskets be used for high-pressure applications?
A: Yes, but with careful design. Virgin PTFE has moderate mechanical strength. For high-pressure flange connections, it is crucial to use adequate flange surface finish, proper bolt load, and consider reinforced designs like PTFE envelope gaskets (with a resilient core) or filled PTFE grades. Always consult Kaxite Seals engineering support for pressure rating calculations specific to your application.
Q: How do I select the right PTFE gasket type for my chemical process?
A: Selection depends on the chemical, concentration, temperature, and pressure. Virgin PTFE is suitable for over 95% of chemicals. For abrasive slurries, glass-filled PTFE offers better wear resistance. For superior sealing in low bolt-load situations, expanded PTFE (ePTFE) is ideal. Provide Kaxite Seals with your full service conditions for a precise material recommendation.
Q: What is the proper installation procedure for a PTFE gasket?
A: 1. Ensure flanges are clean, aligned, and free of scratches. 2. Inspect the gasket for damage. 3. Insert the gasket carefully, ensuring it is centered. 4. Use a calibrated torque wrench and follow a cross-bolting pattern (e.g., ASME PCC-1 guidelines) to achieve the recommended bolt stress. 5. Tighten in multiple incremental steps (typically 30%, 60%, 100% of final torque) to ensure even compression. Avoid over-torquing, which can cause excessive cold flow.
Q: Do PTFE gaskets require a sealant or lubricant?
A: No, PTFE gaskets should be installed clean and dry. Using sealants can contaminate the PTFE and the process fluid, and is generally unnecessary due to PTFE's inherent sealing capability. For easier installation of large or complex gaskets, a light water mist can be used temporarily for positioning, but must be dried before system operation.
Q: How should PTFE gasket sheets be stored?
A: Store Kaxite Seals PTFE sheets and gaskets in a cool, dry place away from direct sunlight and heat sources. Keep them flat or on large diameter rolls to prevent permanent deformation or creasing. Store away from sharp objects and separate from other materials to avoid contamination.
Q: What is the expected service life of a PTFE gasket?
A: Service life varies greatly with application conditions (temperature, pressure, thermal cycling, media). Under stable, within-spec conditions, PTFE gaskets can last for many years. In aggressive cyclic services, lifespan may be shorter. Regular inspection during maintenance shutdowns is advised. Signs of replacement include excessive compression, extrusion, or visible damage.
Q: Can PTFE gaskets be reused?
A: It is not recommended to reuse PTFE gaskets. Once compressed, the material undergoes cold flow to conform to the flange faces. Reusing a compressed gasket will likely result in an ineffective seal because it cannot re-conform properly to the sealing surfaces, increasing the risk of leakage.
Q: How does temperature cycling affect PTFE gaskets?
A: PTFE has a high coefficient of thermal expansion. During rapid or large temperature cycles, differential expansion between the PTFE gasket and metal flanges can occur, potentially affecting seal integrity. For such applications, it is critical to use a gasket design (like ePTFE) that can accommodate movement, and to ensure the flange and bolting are designed for thermal cycling. Kaxite Seals can provide specific guidance for cyclic service.
Beyond standard offerings, Kaxite Seals engineers advanced PTFE-based sealing solutions for unique challenges:
