Frequently used fillers for PTFE compounds and their effects
The information is based on empirical values. It is recommended in concrete applications to ensure the suitability of a compound by means of appropriate tests.
Filler
Typical filler content in %by weight
Effects of the filler
Limits of use / special characteristics
Pigments
up to 25%, maximum 40%
Functional coloration
Observe existing approvals for the pigment
Glass Fibers
up to 25%, maximum 40%
Good abrasion resistance
Strong abrasion of the sliding partner
Well suited to lubricated applications – also frequently used in combination with graphite or molybdenum disulphide
Good chemical resistance against acids
Significant reduction of the cold flow
Increased permeation, channelling along fibers
Grey discolouration in the centre of thicker profiles
If necessary Substance Polymers can also offer a grey-core-free, ‘white’ variant
Carbon
Standard up to 25%; if required up to 33%
Good cold flow reduction
Good abrasion resistance
Good thermal conductivity
Electrically conductive from about 15%
Excellent chemical resistance
Low tool wear during machining
Protects sliding partner, even without dry lubricants
Not stable towards oxidizing media
Makes material brittle
Graphite
Up to 5% or up to 20%
Effective dry lubricant
Usually used as secondary filler in concentrations up to 5%
Low coefficient of friction
Used in concentrations of 20% for good thermal conductivity
Good chemical resistance
High thermal resistance
Not stable towards oxidizing media
High concentration if good thermal conductivity is demanded
Carbon Fibers
Up to 15%
Excellent abrasion resistance
Protects the sliding partner
Resistant to hydrofluoric acid
Good thermal conductivity
Good in water applications, e.g. water pumps
Reduced thermal expansion coefficient
Very good chemical resistance
Good cold flow reduction
Not stable against oxidizing media
Molybdenum Disulphide, MoS₂
Up to 5%, in combination with glass fibers up to 10%
Usually used as secondary filler = dry lubricant (glass fibers, hard carbon, bronze)
Reduces coefficient of friction of compounds
Good chemical resistance
Not resistant against oxidizing acids
Starts to decompose at higher sintering temperatures
