Characteristics of Graphite
- It is an inorganic non-metallic material, but has electrical and thermal conductivity similar to metals.
- The thermal conductivity even exceeds that of metal materials such as steel, iron, and lead.
- Graphite is the most famous solid lubricant with a very low coefficient of friction, so it has been selected as a filler in PTFE for lubrication applications.
- Stable chemical properties, resistant to acid, alkali and organic solvent corrosion.
Graphite Filled PTFE Composite
- The wear resistance of graphite filled PTFE composites is much higher than that of pure PTFE with a very low friction coefficient.
Figure 1. Specific wear rates graphite filled PTFE composites with different content [1]
- With excellent wear resistance, compression creep, chemical resistance, high temperature resistance and electrical conductivity, graphite filled PTFE composites can be used to make bushings, piston rings, guides, seals, etc.
- Thanks to the excellent thermal conductivity, graphite is a better material choice to improve the thermal conductivity of PTFE.
- Graphite-filled PTFE composite material is very suitable for use in high-speed motion and steam environment, and also very suitable for dry friction and oil lubrication friction occasions.
- Graphite can also be filled into PTFE with glass fiber, carbon powder, bronze powder, carbon fiber, etc.
Figure 2. Microstructural images of pure PTFE (a) and PTFE composites filled with graphite + carbon fiber + bronze (h) [1]
- Graphite-filled PTFE composites are not suitable for use in aqueous media. For example, the wear in water is worse than pure PTFE.
- The shape of the filler significantly affects the wear resistance, and the addition of graphite filler particles may increase the wear rate.
- Taking into account the crystallinity due to the filler content, as the graphite load increases, the wear is significantly reduced.
Graphite Filled PTFE Performance Parameter Reference
Table 1. Graphite filled PTFE performance parameter reference
| | Low-filled Graphite/PTFE |
|---|
| Color | Black |
| Density (g/cm3) | 2.15 |
| Shore hardness D | 62 |
| Insulation | Conductive |
| Chemical property | Acid resistance, alkali resistance, corrosion resistance to most chemicals |
Table 2. Comparison of wear test between graphite filled PTFE and pure PTFE under different conditions
| Lubrication conditions | Pure PTFE | Graphite filled PTFE (5%) |
|---|
| Abrasion loss (mg) | Coefficient of friction | Abrasion loss (mg) | Coefficient of friction |
| Dry friction | 122.3 | 0.089 | 26.5 | 0.0114 |
| Oil lubrication | 49.9 | 0.096 | 9.7 | 0.027 |
| Water lubrication | 29.0 | 0.124 | 57.0 | 0.050 |
Note: The above data is for reference only. The actual product in use may vary due to different parts size, raw material batch type, and mechanical working conditions. In addition, the filled PTFE is a multi-element composite material, and the proportioning composition can be adjusted according to the actual working conditions of the customer, which is not fixed.
References
- R. K. Goyal, M. Yadav, Journal of Applied Polymer Science 127 (2012) 3186-3191.
- Alireza Khoddamzadeh, Rong Liu, XijiaWu, Wear 266 (2009) 646–657.
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