Flexible Graphite – Sealing Material with Good Performance Stability

  • High temperature resistance and low thermal expansion coefficient.
  • Good flexibility, resilience and sealing performance.
  • Good corrosion resistant to most acids and bases.
Flexible graphite papers are shown in a fan-shape.

Flexible graphite is a structural compact foil (paper) or sheet made by chemically treating ordinary graphite powder to obtain graphite interlayer compound, and then expanding it at high temperature to get expanded graphite, which is then pressed, baked at high temperature and impregnated. It retains the excellent properties of natural graphite while adding its unique flexibility, resilience, and sealing performance. It can be made into flexible graphite products and graphite sealing products. It is widely used in the sealing of valves, pumps, and reaction vessels under high temperature, high pressure, and corrosion-resistant media. Recently, flexible graphite has been widely used to make fuel cell bipolar plates. In addition to maintaining the electrical conductivity, thermal conductivity, and corrosion resistance of graphite, its simple preparation process also makes it an excellent material for reducing bipolar plate costs.

  • Excellent Heat Resistance
    Flexible graphite can be used up to 3000 °C in a vacuum or reducing atmosphere. It has an extremely low thermal expansion coefficient. It will neither become brittle or crack at low temperatures nor become soften or creep at high temperatures.
  • Good Sealing Performance
    Flexible graphite has high compression resilience, with a general compression ratio of up to 50% and a resilience rate of no less than 20%. When the compression ratio is 12%, the resilience rate can reach 70%. It has a low stress relaxation rate, generally only 1/3 times of that of asbestos sheet. Even it is treated at 100 °C for 22h, its stress relaxation rate generally will not exceed 5%. Additionally, flexible graphite is also impervious.
  • Good Chemical Resistance
    Flexible graphite has excellent stability in almost all acids, bases, salts, organic solvents, oils, and seawater. However, it may corrode in aqua regia, chromic acid, concentrated sulfuric acid, and concentrated nitric acid.
  • Radiation Resistance
    Flexible graphite does not deteriorate and its properties do not change under long-term exposure to various kinds of radiation. This property makes it can b e used as a good sealing material in the nuclear industry and aerospace devices.
Table 1: Specifications of Flexible Graphite
Model Carbon Content Specific Resistance (μΩ·m) Sulfur Content (ppm) Chlorin Content (ppm) Compressive Strength (Mpa) Flexural Strength (Mpa) Tensile Strength (Mpa) Density (g/cm3) Compressing Modulus Rebounding Modulus
GF-2 95%–99.9% 3–7 0–1200 ≤ 35 ≥ 160 ≥ 4.5 1.0(±0.05) ≥ 40%
GP-3 ≥ 99.9% ≤ 1100 ≤ 50 ≥ 40 1.25(±0.05) 30%–35% 10%–12%
GP-4 ≥ 99.9% 3–7 ≤ 1200 ≤ 40 ≥ 40 1.25(±0.05) 30%–35% 19%
  • 1 MPa = 10.2 kgf/cm2; 1 W/m.k = 0.86 kcal/cm.h.°C
  • These properties are typical values and not guaranteed.
Flexible Graphite Paper/Foil

Flexible graphite foil is an excellent sealing material for high temperature, high pressure transfer of liquids, gases, steams, chemicals and corrosives. This material is made of high purity, high crystalline natural flake graphite, which goes through special acid and heat treatment to produce expanded graphite crystals. The expanded graphite crystals are then formed into foil through a calendaring process without any resins and binders.

Flexible Graphite Sheet

Flexible graphite sheets are the basic materials for manufacturing various graphite composite sheets, graphite belts, packing, and sealing gaskets. This material is made from natural flake graphite that is chemically treated and then rolled after high temperature expansion without any resins and binders. It has high temperature resistance, corrosion resistance, radiation resistance, low creep relaxation rate, and excellent flexibility.

Flexible Graphite Gasket

Flexible graphite gaskets are punched or cut from flexible graphite sheets, and have good corrosion resistance, high/low temperature resistance, good compression resilience, and high strength. They are widely used in pipelines, valves, pumps, pressure vessels, heat exchangers, condensers, etc.

Flexible Graphite Packing

Flexible graphite packing are braided from flexible graphite yarns, which are reinforced by cotton fiber, glass fiber, carbon fiber, etc. It has a very low friction and will not damage shafts and stems. Besides, ti has good thermal conductivity, chemical resistance and high resilience. It can be used in valves, pumps, expansion joints, mixers and agitators in high pressure and high temperature conditions and especially suitable for harsh media conditions.