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Engineering Polymers
Precision Shims
Flange GuardsVirgin vs Filled PTFE: How to Choose Glass, Carbon, Bronze, Graphite or MoS₂ PTFE
Short answer: choose virgin PTFE for the widest chemical resistance, electrical insulation and food or pharma contact. Choose a filled PTFE when the part carries load or wears: fillers cut creep (cold flow) and wear many times over. Glass is the all-round filler, carbon suits water and steam, bronze gives the best strength and heat transfer, and graphite or MoS₂ give the lowest friction.
PTFE grades compared
| Grade | Typical filler | Main benefit | Watch out for | Typical uses |
|---|---|---|---|---|
| Virgin PTFE | None | Best chemical resistance, insulation, purity; about −200 °C to +260 °C | Creeps under load, wears quickly | Gaskets, linings, insulators, food and pharma parts |
| Glass-filled | 15–25% glass fibre | Much lower creep and wear, good all-rounder | Abrasive to soft shafts; attacked by HF and strong alkalis | Valve seats, seals, piston rings |
| Carbon-filled | 25–35% carbon (sometimes with graphite) | High wear and compressive strength, good in water and steam | Not for electrical insulation | Piston rings, compressor parts, bearings in water |
| Bronze-filled | 40–60% bronze | Highest strength and thermal conductivity, lowest creep | Poor resistance to acids and corrosive chemicals; conductive | Hydraulic seals, bearing pads, slide plates |
| Graphite-filled | 10–25% graphite | Very low friction, dry running, kind to soft mating surfaces | Lower strength than bronze or carbon grades | Dynamic seals, bushings, dry-running bearings |
| MoS₂-filled | About 5% MoS₂, often with glass | Lower friction and harder surface than glass alone | Usually used in combination, check the exact blend | Seals and bearings with sliding motion |
| Stainless-steel filled | Stainless steel powder | High load and wear, better chemical resistance than bronze | Higher cost; conductive | Heavy-duty seals, wear rings, valve seats |
Three questions that settle the choice
- What chemicals will it touch? If the medium is aggressive (acids, chlorine, solvents), start from virgin PTFE, or glass/carbon filled if you also need wear resistance. Avoid bronze in corrosive service.
- Is it loaded or moving? Static, lightly loaded gaskets can be virgin PTFE. Seals, bearings and slide plates need a filled grade.
- What is the mating surface? Against soft metals or aluminium, prefer graphite or carbon rather than glass, which is abrasive.
All grades are supplied as sheets, rods, tubes and machined parts. Related guide: PTFE vs PP flange guards.
Values are typical figures from published material standards and supplier data, for guidance only. Always check the mill test certificate and your design code for the exact grade you buy.
Need a price or stock check? Send the grade, size and quantity to sales@saifexindustries.com, WhatsApp +971 58 535 2330, or request a formal quote. See our PTFE sheets and rods.
Frequently asked questions
What is the difference between virgin PTFE and filled PTFE?
Virgin PTFE is pure polytetrafluoroethylene with the best chemical resistance and electrical insulation. Filled PTFE adds glass, carbon, bronze, graphite, MoS₂ or steel to reduce creep and wear, at some cost to chemical resistance and insulation.
Which PTFE is best for bearings?
Bronze-filled PTFE for high load and heat, graphite or carbon-filled PTFE for low friction and dry running.
What temperature can PTFE handle?
PTFE is typically used from about −200 °C up to +260 °C in continuous service.
Is glass-filled PTFE food safe?
Virgin PTFE is the usual choice for food and pharmaceutical contact. Some filled grades are available with food-contact compliance; confirm with the material certificate.