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).

 

Possible Variations

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.

STRENGTHS

Wear resistant
Improved hardness
Lower thermal expansion
Lower deformation under load
Non-conductive

WEAKNESSES

Higher coefficient of friction
Abrasive filler unsuitable for some applications
Resistance to gas permeation is reduced

Possible Applications

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
Property Test Method 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
Datasheet: Glass Filled PTFE
AF103 25% Glass Filled PTFE 296kb

Glass fibre is the most commonly used filler in PTFE. It gives much improved compression and wear properties. The material may also be inert gas sintered to further improve creep properties and reduce porosity would be a consequent loss of tensile properties.

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