Carbon Filled PTFE was developed to provide a PTFE based material with improved mechanical strength.
PTFE on its own has excellent frictional properties, elasticity and wear resistance but relatively poor mechanical strength and tends to fail in high PV applications.
Carbon in itself is a brittle material with poor wear properties and mechanical strength. However with the two combined in Carbon Filled PTFE formulations, the resultant material has excellent mechanical and wear properties, retains the excellent frictional properties and is an excellent choice for seals and rings in dynamic and high pressure applications.
Carbon filled PTFE also provides good thermal conductivity, low permeability and is also electrically conductive making it a good choice for anti-static applications
The most common carbon filled PTFE composition is 75% Virgin PTFE with 25% Carbon powder by weight.
When a filler ratio or type is unspecified, it is fair to assume this is the material. However it doesn’t tell the whole story. The type and percentage of carbon added to PTFE is a variable and is critical to material performance.
It can be as little as 0.2% and as much as 40%. Different percentages of carbon will display different material properties and performance.
Something that is often overlooked is that different types of carbon powder can also affect the material integrity and performance. To achieve the optimum physical properties and performance from any filled PTFE it is essential that the properties and type of fillers used are understood.
Not all 25% carbon filled PTFE materials are the same, in fact they can be extremely different.
- Good thermal and electrical conductivity
- Good chemical resistance
- Very economical
- Improved wear resistance under load
- High percentage fillers mean low elongation
- Conductivity can be a problem as well as a strength
Like all PTFE materials and filled grades of PTFE, It is essential to understand that even under a heading like “carbon filled PTFE”, we have many further variables. Materials can be manipulated to offer particular property improvements over others. Even the base grade of PTFE used can display dramatic variations in physical properties and material performance. The secret is knowing which is the right material for any given application and ensuring that is what is being supplied.
AT AFT we offer an almost limitless range of base materials and fillers to suit practically any application.
Typical Physical Properties of carbon Filled PTFE Variations
15% Carbon Filled
|Specific Gravity||ASTM D 792||2.05 – 2.12 g/cm3|
|Tensile Strength||ASTM D 4894||13 – 18 MPa|
|Elongation||ASTM D 4894||90 – 300%|
|Shore D Hardness||ASTM D 2240||60 – 66|
|Deformation Under Load||ASTM D 695||5 – 7%|
|Permanent Deformation||ASTM D 695||2 – 4%|
|Flexural Modulus||1105 MPa|
|Coefficient of Static Friction||0.14 – 0.16|
|Coefficient of Dynamic Friction||0.12 – 0.14|
|Volume Resistivity||ASTM D 257||10-4 Ohm / CM|
|Service Temperature||-2000C / +2600C|