Expanded PTFE Products are high-performance sealing and gasket materials manufactured from 100% virgin polytetrafluoroethylene that has been stretched and expanded to create a microporous, multidirectional fibril structure. Kaxite Sealing supplies a comprehensive range of these products in sheet, tape, gasket, and cord forms to meet demanding industrial sealing requirements. Because of their chemical inertness, broad temperature tolerance, and reliable sealability, expanded PTFE products are widely used in flanged connections, pump housings, heat exchangers, and piping systems across the chemical, pharmaceutical, food, energy, and water treatment sectors.
Expanded PTFE is produced by extruding a fine PTFE paste and then rapidly stretching it under controlled conditions. This process creates a network of microscopic nodes and fibrils that gives the material its unique combination of flexibility, compressibility, and mechanical strength. Unlike conventional skived or molded PTFE, expanded PTFE does not require high bolt loads to conform to irregular flange surfaces. The microporous matrix also allows the material to flow into scratches, weld lines, and flange imperfections, which greatly reduces the risk of leakage in low-pressure and vacuum systems.
Kaxite Sealing controls the expansion ratio, density, and thickness of its expanded PTFE products to ensure consistent performance across every batch. The result is a sealing material that resists cold flow, maintains dimensional stability under thermal cycling, and can be cut or formed easily on site.
Kaxite Sealing offers multiple expanded PTFE product formats to cover different sealing and gasketing needs. Each format is manufactured with consistent density and thickness control to ensure repeatable compression and recovery behavior.
The table below lists typical physical property values for Kaxite Sealing standard white expanded PTFE sheet and gasket materials. Actual values may vary slightly depending on product format and thickness.
| Property | Typical Value | Test Method |
|---|---|---|
| Material | 100% virgin PTFE | — |
| Density | 0.5 – 0.8 g/cm³ | ASTM D792 |
| Continuous service temperature | -268°C to +260°C | — |
| Short-term peak temperature | +315°C | — |
| Maximum operating pressure | Up to 200 bar (depending on flange design and gasket thickness) | — |
| pH range | 0 – 14 | — |
| Tensile strength, longitudinal | 8 – 15 MPa | ASTM D638 |
| Tensile strength, transverse | 6 – 10 MPa | ASTM D638 |
| Elongation at break | 100% – 350% | ASTM D638 |
| Compressibility | 25% – 45% | ASTM F36 |
| Recovery | 9% – 15% | ASTM F36 |
| Creep relaxation at 100°C | Less than 30% | ASTM F38 |
| Sealability | Less than 0.05 mg/(s·m) depending on gas and load | DIN 3535 |
| Color | White standard; blue, black, graphite-filled available | — |
| FDA compliance | FDA 21 CFR 177.1550 | — |
| USP Class VI | Pass | — |
Kaxite Sealing maintains strict dimensional controls across all expanded PTFE products. The following table shows standard tolerance ranges for common product forms.
| Product Form | Thickness Range | Width or Diameter Range | Standard Tolerance |
|---|---|---|---|
| Sheet | 0.5 mm – 6.0 mm | 1000 mm – 1500 mm width, up to 3000 mm length | ±5% of thickness |
| Gasket tape | 1.0 mm – 10.0 mm | 3 mm – 25 mm width | ±10% of width |
| Joint sealant tape | 1.0 mm – 8.0 mm | 3 mm – 25 mm width | ±10% of width |
| Cord | 1.0 mm – 20.0 mm diameter | — | ±0.5 mm |
| Custom gaskets | 0.5 mm – 6.0 mm | Up to 1500 mm OD | ±0.5 mm on ID/OD |
Expanded PTFE products are specified by engineers and maintenance teams in a wide range of industries. Because the material combines chemical inertness with excellent sealability, it often replaces compressed fiber, rubber, and graphite gaskets in aggressive or sensitive process environments.
To achieve maximum performance from expanded PTFE products, proper installation technique is essential. Kaxite Sealing recommends the following procedures for gasket and tape applications.
The best product choice depends on operating temperature, pressure, chemical exposure, flange geometry, and maintenance requirements. For standard raised-face flanges, expanded PTFE sheets cut into gaskets offer excellent reliability. For large-diameter flanges where cutting a single-piece gasket is impractical, expanded PTFE joint sealant tape provides a practical form-in-place solution. For narrow face flanges or dovetail grooves, expanded PTFE cord is often the most effective option.
When temperatures exceed 200°C or pressures exceed 40 bar, Kaxite Sealing recommends selecting a filled expanded PTFE grade, such as silica-filled or graphite-filled material. These grades resist creep more effectively and maintain a tighter seal under extreme conditions. For aggressive oxidizing acids such as fuming nitric acid or hot sulfuric acid, pure white expanded PTFE products are generally preferred because they contain no fillers that could react with the process fluid.
For vacuum service, expanded PTFE gasket tape with a self-adhesive backing can be applied directly to the flange surface and compressed lightly. The material’s conformability helps to seal small leaks and maintain vacuum integrity without requiring high bolt loads. Kaxite Sealing offers technical guidance for selecting the most appropriate density, thickness, and filler content for each application.
Q: What is the maximum temperature for expanded PTFE products?
A: Standard expanded PTFE products can operate continuously from -268°C to +260°C. Short-term exposure up to +315°C is acceptable for most grades. At temperatures above 260°C, PTFE begins to soften and may exhibit increased creep, so bolt load retention becomes more important. For applications involving sustained high temperatures near the upper limit, Kaxite Sealing recommends using a filled grade or a thicker gasket to compensate for potential relaxation. At cryogenic temperatures, expanded PTFE remains flexible and does not become brittle, which makes it a good choice for liquid oxygen, liquid nitrogen, and other cold process connections.
Q: Can expanded PTFE gasket tape be used on damaged or pitted flanges?
A: Yes. One of the key advantages of expanded PTFE products is their ability to conform to irregular flange surfaces. The microporous fibril structure compresses under low bolt load and flows into scratches, pits, and minor surface imperfections. For deeply pitted or heavily corroded flanges, a thicker tape or sheet is usually recommended. In many cases, a 3 mm to 6 mm thick expanded PTFE tape can seal a flange that would otherwise require resurfacing or replacement. However, the flange must still have enough structural integrity to maintain bolt load, and severe radial grooves that extend across the sealing face should be repaired before installation.
Q: Are expanded PTFE products suitable for food and pharmaceutical applications?
A: Yes. Kaxite Sealing expanded PTFE products are manufactured from 100% virgin PTFE and meet FDA 21 CFR 177.1550 for repeated food contact. Many grades also pass USP Class VI testing for medical and pharmaceutical applications. The material is non-toxic, non-absorbent, and resistant to cleaning agents used in CIP and SIP systems. Because expanded PTFE does not contain binders, pigments, or organic fibers, it does not promote bacterial growth or contaminate process fluids. White expanded PTFE sheets and gaskets are commonly used in sanitary flanges, filter housings, and reactor manways in food, beverage, and pharmaceutical plants.
Q: How does expanded PTFE compare to conventional PTFE gasket material?
A: Conventional skived or molded PTFE is very rigid and tends to creep significantly under load, which can cause gasket leaks over time. Expanded PTFE products have a much more open, fibrous structure that improves compressibility and recovery while reducing cold flow. This means expanded PTFE seals at lower bolt loads, conforms better to flange imperfections, and retains torque longer than conventional PTFE. In addition, expanded PTFE is easier to cut and handle, and it does not require the same degree of flange flatness. The trade-off is that expanded PTFE has slightly lower tensile strength than solid PTFE, but for most static sealing applications the improved conformability and creep resistance offer a clear advantage.
Q: What is the recommended bolt torque for expanded PTFE gaskets?
A: Expanded PTFE products typically require much lower seating stress than fiber or metal gaskets. A common target seating stress is 10 to 30 MPa, depending on the gasket thickness and operating pressure. Bolt torque should be calculated based on flange size, bolt material, lubricant condition, and gasket area. As a general guideline, many standard ANSI flanges with expanded PTFE gaskets are tightened to 20 to 40 Nm for small flanges and 80 to 200 Nm for larger flanges, but the correct value should always be determined from the flange design standards and gasket supplier recommendations. Kaxite Sealing provides bolt torque tables for standard flange classes and can assist with specific calculations.
Q: Can expanded PTFE products be used with strong acids and alkalis?
A: Yes. Expanded PTFE is chemically inert to virtually all acids, alkalis, solvents, and process fluids across the entire pH range of 0 to 14. It is compatible with hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, sodium hydroxide, chlorine, ammonia, and most organic solvents. The only chemicals that can attack PTFE are molten alkali metals such as sodium or potassium at high temperature and elemental fluorine gas under certain conditions. Because of this broad compatibility, expanded PTFE products are commonly used in chemical dosing skids, acid transfer lines, scrubbers, and storage tank manways where other gasket materials would degrade quickly.
Q: How long do expanded PTFE products last in storage?
A: Expanded PTFE products have an indefinite shelf life when stored in a clean, dry environment away from direct sunlight and extreme heat. Unlike rubber or fiber-based gaskets, PTFE does not oxidize, harden, or lose flexibility over time. The material is not affected by humidity or UV light, and it does not require special packaging. Kaxite Sealing recommends keeping sheets and tapes in their original packaging or a sealed plastic bag to prevent dust and dirt from contaminating the sealing surface. Before installation, visually inspect the material for cuts, creases, or handling damage, but no special storage conditioning is required.
Q: Can expanded PTFE tape be used in vacuum service?
A: Yes. Expanded PTFE joint sealant tape and gasket tape are often used in vacuum systems because the material is dense, low-permeability, and highly conformable. The tape can be applied directly to the flange face and compressed lightly to form an effective seal. For high-vacuum or very low-pressure applications, a slightly thicker tape or sheet may be required to compensate for the limited bolt load available. Expanded PTFE products do not outgas significantly and do not contain plasticizers or binders that could contaminate vacuum chambers. In semiconductor and analytical instrument applications, high-purity white expanded PTFE grades from Kaxite Sealing are frequently selected for this reason.
