Graphite Properties
Graphite is the standard material for high-temperature gaskets and self-lubricating bearings. Learn its unique properties and industrial applications.
Overview
Graphite is a crystalline form of carbon with a layered structure that gives it unique properties: self-lubrication, high temperature resistance, chemical inertness, and thermal conductivity. It is used extensively in gaskets, packing, bearings, and as a thermal interface material.
Key Properties
| Property | Value | |
|---|---|---|
| Density | 2200 kg/m³ | |
| Max service temperature | 500°C (air), 3000°C (inert) | Oxidation limits use in air |
| Thermal conductivity | 120–200 W/m·K (in-plane) | Anisotropic |
| Coefficient of friction | 0.1–0.15 (self-lubricating) | |
| Chemical resistance | Excellent (most chemicals) |
Advantages
- Self-lubricating: The layered structure allows layers to slide over each other — natural solid lubricant, no oil needed.
- High temperature resistance: Up to 500°C in air, 3000°C in inert atmosphere — far exceeds any polymer.
- Chemically inert: Resists most acids, alkalis, and solvents — used in chemical plant gaskets.
- Thermally conductive: Conducts heat away from sealing surfaces — prevents localised overheating.
- Conformable: Flexible graphite (exfoliated) conforms to irregular flange surfaces — excellent seal.
Limitations
- Oxidation in air above 500°C: Graphite burns in air at high temperatures — use in inert atmosphere for higher temps.
- Mechanically weak: Low tensile strength — not a structural material. Used as gasket/packing, not as load-bearing component.
- Messy: Graphite marks and stains — can be a contamination concern in clean environments.
- Galvanic corrosion risk: Graphite is cathodic to most metals — can accelerate corrosion of steel flanges in wet environments. Use with corrosion inhibitor or pick a different gasket for wet service.
Typical Applications
- High-temperature gaskets (spiral wound, exfoliated)
- Valve stem packing (graphite yarn)
- Pump packing rings
- Self-lubricating bearings and bushings
- Heat shields and furnace components
- Electrical brushes and contacts
Chemical Compatibility
| Chemical | Rating |
|---|---|
| Acids (most) | Excellent |
| Alkalis | Excellent |
| Organic solvents | Excellent |
| Oxidising acids (conc.) | Fair |
| Steam (high temp) | Excellent |
| Oils and fuels | Excellent |
How CHI can help
Ask CHI about graphite properties and to recommend graphite gaskets for your high-temperature flange application. The CHI assistant can recommend the right material for your specific application, explain chemical compatibility, and flag when a material is unsuitable for your operating temperature or environment.