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

 

Possible Variations

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.

STRENGTHS

Good thermal and electrical conductivity
Good chemical resistance
Very economical
Improved wear resistance under load

WEAKNESSES

High percentage fillers mean low elongation
Conductivity can be a problem

Possible Applications

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
Property Test Method 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
Datasheet: Carbon Filled PTFE
AF207 15% Carbon Filled PTFE 183kb

Carbon filled PTFE has excellent compressive strength, wear and chemical resistance. It provides good thermal conductivity and low permeability. An ideal material for dynamic sealing applications.

AF201 25% Carbon Filled PTFE 294kb

The addition of Carbon Fibre to PTFE increases the compressive strength and wear resistance. It provides good thermal conductivity and low permeability. Commonly used in sealing applications.

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