Filled PTFE
Filled PTFE adds glass, carbon, graphite, bronze or other fillers to PTFE, greatly improving wear resistance, creep resistance and thermal conductivity while keeping low friction and chemical resistance. It is used for seals, piston rings, bearings and valve seats under load.
What it is
Each filler changes properties: glass (15–25%) improves wear and creep at low cost; carbon/graphite suits dry running and water; bronze (40–60%) gives the best wear and thermal conductivity; polyimide fillers are gentle on soft mating surfaces.
Filled PTFE is chosen to match the mating surface, medium and pressure-velocity (PV) conditions.
Typical applications
- Hydraulic and pneumatic seals and wear rings
- Compressor piston rings and rider bands
- Bearing bushes and slide pads
- Valve seats and ball seats
- Chemical pump parts
Materials & grades
- Glass-filled PTFE (15–25%)
- Carbon/graphite-filled PTFE
- Bronze-filled PTFE (40–60%)
- MoS2 and polyimide-filled PTFE
Points to consider
- Bronze-filled PTFE is not suitable for corrosive media or electrical insulation.
- Glass-filled grades can wear soft shafts; choose carbon or polyimide fillers there.
- Filled grades lose some chemical resistance compared to virgin PTFE.
- Colour identifies filler type (e.g. bronze is brown, carbon is black).
Frequently asked questions
Why add fillers to PTFE?
To dramatically improve wear and creep resistance and thermal conductivity while keeping low friction.
Which filled PTFE is best for seals?
It depends on the mating surface and medium: glass for general use, carbon/graphite for water and dry running, bronze for high loads in oil.
Is filled PTFE food safe?
Some grades are; fillers affect compliance, so check specific grades for food contact.