PTFE 25%: Properties, Uses & Cost Guide
Tensile data verified against MatWeb.com database & manufacturer datasheets · Last updated July 2026
Published: 2026-06-08
PTFE 25% glass-filled combines the universal chemical resistance of pure PTFE with significantly improved dimensional stability and wear resistance. The glass fiber filler reduces the cold-flow (creep) that limits unfilled PTFE in load-bearing...
PTFE 25% glass-filled combines the universal chemical resistance of pure PTFE with significantly improved dimensional stability and wear resistance. The glass fiber filler reduces the cold-flow (creep) that limits unfilled PTFE in load-bearing applications — compressive strength increases by approximately 40% compared to virgin PTFE. This grade is specified for: pump wear rings, lip seals in chemically aggressive environments, valve seats handling strong acids at moderate temperatures, and electrical insulators requiring both chemical inertness and mechanical stability. The trade-off: glass fibers make this grade mildly abrasive to mating surfaces — soft metal shafts running against 25GF PTFE bearings will experience accelerated wear unless hardened or coated.
Recommended Applications
PTFE 25% Glass-Filled is commonly specified for:
⚠ Not Recommended For
PTFE 25% Glass-Filled is not recommended for:
- Structural load-bearing applications (tensile strength only 20-30 MPa; PEEK or PAI preferred)
- High-pressure sealing without backup rings (PTFE creeps under sustained load — cold flow)
- Vacuum applications without special processing (PTFE outgasses significantly; use FEP or PFA for vacuum)
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Selection & Application Guide
PTFE is unmatched when your primary requirement is chemical inertness or the lowest possible coefficient of friction. Choose PTFE over PEEK when the application involves sliding contact, non-stick requirements, or aggressive chemicals at moderate temperatures (below 260°C). Avoid PTFE when structural load-bearing is needed — its tensile strength (20-30 MPa) is among the lowest of engineering plastics. PTFE cannot be melt-processed by injection molding; it requires compression molding and sintering.
Real-World Applications
PTFE's virtual chemical inertness makes it the standard for seals and gaskets in chemical processing equipment handling strong acids, bases, and solvents at temperatures up to 260°C.
PTFE's extremely low coefficient of friction (0.05-0.10) makes it the universal choice for non-stick cookware, conveyor belts, and chute liners where material buildup must be prevented.
PTFE's dielectric constant (2.1) and dissipation factor remain stable across a wide frequency and temperature range — ideal for high-frequency RF cables and microwave components.
Filled PTFE (glass, carbon, bronze) grades provide wear-resistant bearing surfaces for unlubricated or marginally lubricated applications in pumps and compressors.
Processing & Cost Considerations
Manufacturing Tips
- PTFE cannot be injection molded — it does not flow when heated. It is processed by compression molding (pre-forming) followed by sintering at 360-380°C. This limits part geometry complexity compared to injection-moldable polymers.
- Filled PTFE compounds (15-25% glass fiber, 15-25% carbon, or 40-60% bronze) dramatically improve wear resistance and reduce creep. Select filled grades for bearing and seal applications; use unfilled PTFE only for maximum chemical purity.
- PTFE has very high thermal expansion (10× that of steel). Design generous tolerances and clearance fits for PTFE components that will see temperature cycling.
Unfilled PTFE costs $25-60/kg — significantly less than PEEK but more than commodity plastics. The real cost driver is processing: compression molding and sintering is slower and less automated than injection molding. Glass-filled PTFE is 10-20% more expensive but offers 5-10× better wear resistance, often reducing total system cost. PTFE tubing and tape command premium prices due to specialized extrusion requirements.
Technical Properties
| Density | 2.22 g/cm³ |
|---|---|
| Tensile Strength | 25 MPa |
| Melting Point | 327 °C |
| Shrinkage Rate | 1.5-2.5% |
| Flexural Modulus | 1.8 GPa |
| Hdt | 120 °C at 1.82 MPa |
Engineering Tool: Shrinkage & Cost Estimator
Calculate part weight, mold cavity dimensions accounting for shrinkage, and material cost — all locally in your browser.
Equivalents & Cross-References
| Equivalent / Alternate | Action |
|---|---|
| Teflon 25GF | |
| Fluorosint 500 |
Frequently Asked Questions
When should I use glass-filled PTFE instead of virgin PTFE?
When the application involves compressive loads or requires dimensional stability. Virgin PTFE cold-flows (creeps) under sustained load — gaskets lose bolt tension over time, bearing clearances change. Glass-filled PTFE resists creep approximately 3-5× better than virgin PTFE. The downside is reduced chemical resistance (glass fibers can be attacked by hydrofluoric acid and strong alkalis) and abrasiveness to mating surfaces.
Is glass-filled PTFE FDA-compliant for food contact?
Some grades are — specifically those using FDA-compliant glass fiber sizing. Check the manufacturer's certification. Unfilled PTFE is universally FDA-compliant; filled grades require verification. For pharmaceutical and food processing, consider PTFE with FDA-compliant fillers or unfilled PTFE with modified processing to improve creep resistance.
Why can't PTFE be injection molded?
PTFE's melting point (327°C) is well below its processing temperature, but it does not transition to a flowable melt. Above 327°C, PTFE becomes a gel-like translucent material with extremely high viscosity — it cannot be forced through a mold gate. This is why PTFE is always processed by compression molding and sintering, ram extrusion, or paste extrusion.
Is PTFE safe for food contact?
Yes. PTFE is FDA-compliant under 21 CFR 177.1550 for repeated food contact. However, PTFE should not be heated above 350°C as it begins to decompose, releasing fumes that can cause polymer fume fever in humans. Normal cooking temperatures are well below this threshold.
What is the difference between PTFE and PFA?
PFA (perfluoroalkoxy) is a melt-processable fluoropolymer with similar chemical resistance and temperature capability to PTFE. PFA can be injection molded and extruded like conventional thermoplastics, making it suitable for complex geometries that PTFE cannot achieve. PFA costs roughly 2× PTFE and has slightly lower maximum service temperature (260°C vs 260°C — equivalent, but PTFE handles short-term peaks better).
How does PTFE compare to FEP?
FEP (fluorinated ethylene propylene) is another melt-processable fluoropolymer with similar chemical resistance to PTFE but lower maximum service temperature (200°C vs 260°C for PTFE). FEP is transparent, easier to process, and less expensive than PFA. Use FEP when transparency and melt processability are needed below 200°C; use PFA when temperatures approach 260°C.
Can PTFE be welded?
No. PTFE cannot be welded by conventional thermoplastic methods (hot plate, ultrasonic, or heat sealing) because it does not melt into a flowable state. PTFE components are joined by mechanical fastening, adhesive bonding (with surface treatment like sodium etching), or by using PTFE-coated metal flanges with gaskets.
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References & Industry Standards
- ASTM International. Standard Specifications for Engineering Plastics & Thermoplastics. astm.org
- UL Prospector. Plastics & Elastomers Material Database. ulprospector.com
- MatWeb. Material Property Data for Engineering Thermoplastics. matweb.com
- ISO 1043. Plastics — Symbols and Abbreviated Terms. iso.org