Glass fibre is the most commonly used filler in PTFE.
Glass fibre is used as a PTFE filler as it offers much improved compression and wear properties. The material may also be inert gas sintered to further improve creep properties and reduce porosity and gas permeability (there would be a consequent loss of tensile properties).
Glass Filled PTFE is reinforced with glass fibres with the percentage varying between 5% and 40% depending on the needs of the application. As the filler percentage increases so does the benefits the filler offers (increased compressive strength, lower deformation under load) but conversely the coefficient of friction properties of the material increases over that of virgin PTFE.
- Wear resistant
- Improved hardness
- Lower thermal expansion
- Lower deformation under load
- Higher coefficient of friction
- Abrasive filler unsuitable for many dynamic applications
- Resistance to gas permeation is reduced
Glass filled PTFE is very commonly used in valve seat applications. Increased compressive strength and creep resistance of the material allow much greater pressure on the valve seat and as such a much higher rated valve.
Other applications include:
Pump housings, valve seats, gaskets, roller coverings, shaft bearings, filter housings, etching plates, shaft seals, slide runners, chemical engineering, machine parts, transport and conveyor technology, pump and instrument construction, electrical industry, electronics, laser technology, fume purification, pure water production, cryogenics, filter technology, food and medical technology.
Typical Physical Properties of Glass Filled PTFE Variations
25% Glass Filled
|Specific Gravity||ASTM D 4894||2.23 – 2.26 g/cm3|
|Tensile Strength||ASTM D 4894||31 MPa (4600 PSI)|
|Elongation||ASTM D 4894||>180%|
|Shore D Hardness||BS EN 13000-2||60|
|Compressive Strength 1% Deformation||>9 MPa|
|Compressive Modulus||ASTM D695||758 MPa|
|Flexural Strength||ASTM D790||13.4 MPa|
|Flexural Modulus||ASTM D790||1310 MPa|
|Coefficient of Linear Thermal Expansion||ASTM D696||7.7-11.2 x10-5°C (100°C)|
|Thermal Conductivity||C177||10.6 x 10-4 cal/cm-sec-°C|