In high-performance sealing applications, Graphite Filled PTFE stands out as a versatile material that addresses the limitations of virgin PTFE while retaining its outstanding chemical resistance. This composite is produced by uniformly dispersing fine graphite particles into a polytetrafluoroethylene matrix, creating a dense, black thermoplastic material with improved mechanical, thermal and tribological properties. Kaxite Sealing supplies Graphite Filled PTFE in sheet, rod, tube and custom-machined forms for industries such as chemical processing, oil and gas, power generation, pharmaceutical manufacturing and food equipment.
The addition of graphite—typically at 15% or 25% by weight—significantly reduces the cold flow and creep that virgin PTFE experiences under load. It also increases thermal conductivity, allowing heat to dissipate more efficiently in dynamic sealing applications. At the same time, the material retains a low coefficient of friction, outstanding dielectric properties and nearly universal chemical compatibility. These characteristics make Graphite Filled PTFE an excellent choice for gaskets, seals, bearings, wear rings, valve seats and pump components operating in demanding environments.
Kaxite Sealing manufactures Graphite Filled PTFE using high-purity raw materials and a controlled compression molding and sintering process. Each production batch is tested for density, tensile strength, hardness, compressibility and thermal conductivity to ensure consistent performance. The material is available in a range of thicknesses, sheet sizes and rod diameters, and can be supplied as finished machined parts according to customer drawings.
Virgin PTFE is known for its excellent chemical resistance and low friction, but its mechanical properties limit its use in load-bearing or high-pressure sealing applications. Under sustained compressive stress, virgin PTFE tends to creep or cold flow, which can lead to gasket thinning, loss of bolt load and eventual leakage. Graphite filler changes this behavior by creating a harder, more dimensionally stable composite without sacrificing the base polymer's desirable attributes.
The graphite particles act as solid lubricants and thermally conductive pathways. They reduce friction between mating surfaces, improve wear resistance and help transfer frictional heat away from the sealing interface. This is especially important in rotary shaft seals, piston rings and compressor components where localized heat buildup can degrade the seal material. Graphite Filled PTFE also shows better resistance to deformation under load, making it suitable for use in flanges with high gasket seating stresses.
Another advantage is the material's reduced thermal expansion compared to virgin PTFE. Graphite has a low coefficient of thermal expansion, so the composite remains more stable across a wide temperature range. This dimensional stability reduces the risk of seal extrusion and improves performance in applications with frequent temperature cycling. Kaxite Sealing recommends Graphite Filled PTFE for services where virgin PTFE has failed due to creep, extrusion or heat buildup.
Kaxite Sealing offers two standard grades of Graphite Filled PTFE: KS-G15 and KS-G25. KS-G15 contains 15% graphite by weight and is the most commonly specified grade for gaskets and static seals where a balance of chemical resistance, conformability and strength is required. KS-G25 contains 25% graphite by weight and provides higher thermal conductivity, lower friction and better wear resistance, making it ideal for dynamic seals, bearings and wear rings.
Both grades are produced as compression-molded sheets, skived sheets, extruded rods and molded tubes. Custom formulations with different graphite particle sizes or additional fillers such as carbon fiber, glass fiber or molybdenum disulfide can be developed for specific applications. All Kaxite Sealing Graphite Filled PTFE products are free from asbestos and comply with major environmental and safety regulations.
| Property | KS-G15 (15% Graphite) | KS-G25 (25% Graphite) | Test Method |
|---|---|---|---|
| Filler content | 15% by weight | 25% by weight | Internal control |
| Color | Black | Black | Visual |
| Density | 2.10 - 2.20 g/cm³ | 2.00 - 2.10 g/cm³ | ASTM D792 |
| Tensile strength | ≥ 15 MPa | ≥ 12 MPa | ASTM D638 |
| Elongation at break | ≥ 150% | ≥ 100% | ASTM D638 |
| Hardness | 60 - 65 Shore D | 62 - 68 Shore D | ASTM D2240 |
| Compressibility at 14 MPa | 4 - 6% | 3 - 5% | ASTM F36 |
| Recovery | ≥ 35% | ≥ 30% | ASTM F36 |
| Coefficient of friction (dry vs steel) | 0.04 - 0.08 | 0.03 - 0.07 | ASTM D1894 |
| Thermal conductivity | 0.55 - 0.70 W/m·K | 0.65 - 0.80 W/m·K | ASTM C177 |
| Continuous service temperature | -200°C to +260°C | -200°C to +260°C | Internal evaluation |
| Maximum short-term temperature | +300°C | +300°C | Internal evaluation |
| Maximum static pressure | 8 MPa | 8 MPa | Depending on gasket geometry |
| Volume resistivity | 10⁶ - 10⁹ Ω·cm | 10³ - 10⁶ Ω·cm | ASTM D257 |
| Product Form | Standard Dimensions | Tolerance |
|---|---|---|
| Sheet thickness | 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm | ±0.05 mm up to 2 mm; ±0.10 mm over 2 mm |
| Sheet size | 1500 mm x 1500 mm, 1200 mm x 1200 mm, 1000 mm x 1000 mm, 1500 mm x 3000 mm | ±2 mm |
| Rod diameter | 10 mm to 300 mm | ±0.05 mm to ±0.20 mm depending on diameter |
| Rod length | 500 mm, 1000 mm, 2000 mm | +10 mm / -0 mm |
| Tube outer diameter | 20 mm to 500 mm | ±0.10 mm to ±0.50 mm |
| Tube wall thickness | 3 mm to 50 mm | ±0.10 mm to ±0.30 mm |
Kaxite Sealing can also produce non-standard dimensions and custom thicknesses up to 50 mm on request. Sheets over 6 mm are typically molded rather than skived to ensure uniform filler distribution and consistent mechanical properties throughout the cross-section. For machined parts, dimensional tolerances of ±0.05 mm are achievable, and tighter tolerances can be discussed for critical sealing geometries.
Graphite Filled PTFE retains the broad chemical resistance of virgin PTFE in most service conditions. The PTFE matrix is inert to virtually all industrial chemicals, while the graphite filler may be affected by strong oxidizing agents at elevated temperatures. The table below summarizes compatibility with common chemical classes.
| Chemical Class | Compatibility | Notes |
|---|---|---|
| Organic solvents (ketones, esters, alcohols, aliphatic hydrocarbons) | Excellent | No swelling or degradation up to 260°C |
| Aromatic hydrocarbons (benzene, toluene, xylene) | Excellent | Retains dimensional stability |
| Strong alkalis (sodium hydroxide, potassium hydroxide) | Excellent | Graphite filler stable in alkaline media |
| Weak acids (acetic acid, citric acid, phosphoric acid) | Excellent | No measurable attack |
| Strong mineral acids (hydrochloric acid, sulfuric acid at moderate concentration and temperature) | Good to Excellent | Graphite may oxidize in hot concentrated sulfuric acid above 150°C |
| Strong oxidizing acids (hot concentrated nitric acid, chromic acid) | Limited | Not recommended due to graphite oxidation |
| Steam and hot water | Excellent | Low moisture absorption and no hydrolysis |
| Halogens (chlorine, bromine) below 100°C | Good | Fluorine gas is not recommended |
| Food and pharmaceutical media | Good | Use only grades specifically approved for food contact |
When a process stream contains strong oxidizing agents or high concentrations of hot nitric acid, Kaxite Sealing recommends evaluating a different PTFE compound such as glass-filled PTFE or a virgin PTFE product. For most other chemical services, Graphite Filled PTFE performs reliably and provides an extended service life compared to standard PTFE.
Graphite Filled PTFE is used in sealing and bearing applications where both chemical resistance and mechanical strength are necessary. Its low friction and high thermal conductivity make it particularly suitable for dynamic seals that generate heat during operation. Typical applications include:
Kaxite Sealing supplies Graphite Filled PTFE as both semi-finished stock shapes and finished parts. When machining Graphite Filled PTFE, sharp carbide or diamond-tipped tools with high positive rake angles should be used to produce clean cuts and avoid tearing the material. Because the graphite filler is abrasive, tool wear is higher than when machining virgin PTFE, so tool life should be monitored closely.
The material can be turned, milled, drilled, sawed and CNC-machined to tight tolerances. Coolant is generally not required for light cuts, but compressed air or a water-soluble coolant can help dissipate heat and extend tool life during heavy machining. Finished parts should be cleaned with mild detergents or alcohol before installation to remove any machining residues. Graphite Filled PTFE can also be skived into thin films and tapes for specific gasket configurations.
When cutting sheets into gaskets, water jet cutting is preferred because it produces smooth edges without introducing heat-affected zones. Laser cutting is possible but may leave a darkened edge due to the graphite content. Stamping and die cutting are suitable for large production runs of thin sheets up to 3 mm thick.
Graphite Filled PTFE is a composite material in which fine graphite particles are uniformly dispersed throughout the PTFE matrix. This reinforcement reduces the cold flow and creep that virgin PTFE experiences under load, increases thermal conductivity and improves wear resistance. Virgin PTFE has a thermal conductivity of approximately 0.25 W/m·K, while graphite-filled grades typically range from 0.55 to 0.80 W/m·K. The graphite also acts as a solid lubricant, so the coefficient of friction remains low even under dry running conditions. In short, Graphite Filled PTFE offers the chemical resistance of PTFE with better mechanical strength and heat dissipation for demanding sealing applications.
The continuous service temperature for Kaxite Sealing Graphite Filled PTFE is -200°C to +260°C. Short-term exposure up to +300°C is possible, but sustained operation above 260°C may cause thermal degradation of the PTFE matrix and reduce seal life. At elevated temperatures, the graphite filler can also oxidize if the environment contains air or strong oxidizing agents. For applications approaching the upper temperature limit, Kaxite Sealing recommends evaluating the specific flange geometry, gasket seating stress and process media to confirm suitability.
Yes. Graphite Filled PTFE is resistant to most organic solvents, strong alkalis, weak acids and many mineral acids. However, the graphite filler is vulnerable to oxidation by strong oxidizing acids such as hot concentrated nitric acid or chromic acid. In such services, glass-filled PTFE or virgin PTFE may be a better choice. For most hydrocarbon, chlorinated solvent, steam and dilute acid applications, Graphite Filled PTFE provides excellent chemical compatibility and reliable long-term performance.
Graphite acts as a solid lubricant within the PTFE matrix. It forms a thin transfer film on mating metal surfaces, reducing direct contact between the seal and the shaft or flange face. This lowers friction, minimizes stick-slip behavior and improves wear resistance in dynamic applications. The dry coefficient of friction for Kaxite Sealing Graphite Filled PTFE is typically between 0.03 and 0.08 against steel, depending on the graphite content, surface finish and contact pressure. This makes the material an excellent choice for bearings, piston rings and rotary seals where low friction and long service life are critical.
Kaxite Sealing offers Graphite Filled PTFE sheets in standard thicknesses ranging from 0.5 mm to 6.0 mm. Common sizes include 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 3.0 mm, 4.0 mm, 5.0 mm and 6.0 mm. Sheets over 6 mm are available as molded plates up to 50 mm thick. Standard sheet dimensions are 1500 mm x 1500 mm, 1200 mm x 1200 mm, 1000 mm x 1000 mm and 1500 mm x 3000 mm. Custom thicknesses and non-standard sheet sizes can be produced on request.
Graphite Filled PTFE is generally not recommended for use in pure oxygen or oxygen-enriched environments because the graphite filler can oxidize, especially at elevated temperatures and pressures. In oxygen systems, the risk of combustion or rapid oxidation increases when organic materials with carbon-based fillers are present. For oxygen service, Kaxite Sealing recommends using virgin PTFE or a specialized oxygen-compatible sealing material that has been tested and approved for the specific pressure and temperature conditions.
Before installation, the flange faces should be clean, dry and free from scratches, rust or old gasket material. The Graphite Filled PTFE gasket should be centered between the flanges and compressed evenly using a star pattern tightening sequence. Apply torque in three or four passes to gradually seat the gasket. Because Graphite Filled PTFE has low creep compared to virgin PTFE, it maintains bolt load better over time, but a re-torque after the first thermal cycle is still recommended. Avoid excessive gasket seating stress beyond the maximum pressure rating to prevent material extrusion.
Yes. Kaxite Sealing provides custom machining services for Graphite Filled PTFE parts based on customer drawings or samples. Capabilities include CNC turning, milling, drilling, water jet cutting and die cutting. The company can produce custom gaskets, valve seats, piston rings, bearing pads, wear rings, custom rods and tubes in both KS-G15 and KS-G25 grades. Tolerances as tight as ±0.05 mm are achievable on machined parts, and prototype quantities as well as full production volumes are supported.
