PTFE-C25 C25
Additive grade · default condition
C25 = 25% carbon powder filled
Default general-purpose carbon-filled PTFE for dry-running piston/guide rings, valve seats and hydraulic seals.
Values for the C25 condition
Other PTFE-C25 grades and fills
PTFE-C25 is listed in 5 conditions; see the grade overview at PTFE-C25.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Conductive carbon black filled | Choose when only static dissipation is required and near-virgin mechanical properties must be kept. | 10 | 20 | 220 | 58 Shore D |
25% carbon + 5% graphite | Pick for dry-running oil-free compressor piston/rider rings: lowest friction and best PV of the carbon family. | 11 | 14 | 75 | 66 Shore D |
15% carbon powder filled | Lower filler loading when more ductility/sealability is needed and wear duty is moderate. | 12 | 17 | 130 | 62 Shore D |
C25DefaultThis page 25% carbon powder filled | Default general-purpose carbon-filled PTFE for dry-running piston/guide rings, valve seats and hydraulic seals. | 12 | 15 | 90 | 65 Shore D |
20% carbon powder filled | Intermediate loading balancing wear resistance and elongation for dynamic seals. | 12 | 16 | 110 | 64 Shore D |
What is PTFE-C25 C25?
PTFE-C25 C25 is PTFE-C25 in the C25 grade — default general-purpose carbon-filled PTFE for dry-running piston/guide rings, valve seats and hydraulic seals. PTFE-C25 C25 has a yield strength of 12 MPa (1.74 ksi) and a tensile strength of 15 MPa (2.18 ksi) — weaker than 88% of polymer grades. Elongation at break is 90% and the elastic modulus is 1 GPa (0.145 Msi). PTFE-C25 C25 has a density of 2.08 g/cm³ (0.0751 lb/in³), heavier than 98% of polymer grades. Its glass-transition temperature is 120°C (248 °F).
Advantages
- Good UV / weathering resistance — 98/100, better than 99% of polymer grades
- Conducts heat well — 0.5 W/m·K (0.289 BTU/hr·ft·°F), better than 98% of polymer grades
- High service temperature — 260°C (500 °F), better than 97% of polymer grades
- Low moisture uptake — 0.02%, better than 92% of polymer grades
- Good corrosion resistance — 90/100, better than 82% of polymer grades
Limitations
- Heavy — 2.08 g/cm³ (0.0751 lb/in³), worse than 98% of polymer grades
- High mold shrinkage — 2.5%, worse than 93% of polymer grades
- Hard to polish — 25/100, worse than 90% of polymer grades
- Difficult to weld — 5/100, worse than 89% of polymer grades
- Low strength — 12 MPa (1.74 ksi), worse than 88% of polymer grades
PTFE-C25 C25 properties
Typical room-temperature values for PTFE-C25 C25; 26 are specific to this condition. Other listed values are PTFE-C25 reference data and may not represent this condition. Bars are the position among polymer grades.
Physical5
PTFE-C25 C25 has a density of 2.08 g/cm³ (0.0751 lb/in³), heavier than 98% of polymer grades. Its glass-transition temperature is 120°C (248 °F).
Mechanical15
PTFE-C25 C25 has a yield strength of 12 MPa (1.74 ksi) and a tensile strength of 15 MPa (2.18 ksi) — weaker than 88% of polymer grades. Elongation at break is 90% and the elastic modulus is 1 GPa (0.145 Msi).
Thermal10
PTFE-C25 C25 is rated for continuous service to 260°C (500 °F). It conducts heat at 0.5 W/m·K (0.289 BTU/hr·ft·°F), better than 98% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical3
PTFE-C25 C25 has an electrical resistivity of 10 Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 82% of polymer grades. UV resistance is excellent.
Sustainability4
Producing a kilogram of PTFE-C25 C25 takes about 165 MJ of energy and emits 8.5 kg of CO₂ — more than 86% of polymer grades. Typical recycled content is 0%.
Manufacturability6
PTFE-C25 C25's machinability is very good (70/100, better than 74% of polymer grades); weldability not recommended (5/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PTFE-C25 C25
Is PTFE-C25 easy to machine?
Turns and mills easily with sharp positive-rake carbide or PCD tools and light clamping; the coke filler is abrasive so tools dull faster than on virgin PTFE, and fine conductive dust needs extraction.
Can PTFE-C25 be welded?
Cannot be fusion or solvent welded; join by mechanical clamping, bonding after sodium-etch/plasma surface activation, or by re-sintering in a mould.
Can PTFE-C25 be formed, bent or molded?
Not melt-processable — preform is cold compression-moulded then free-sintered at ~370–380 °C with slow cool; ram extrusion is used for rod and tube, allow ~2–3% sinter shrinkage.
What surface finishes work on PTFE-C25?
Machined surfaces stay matte black and cannot be painted or plated without etching; deburr with sharp blades, and stress-relieve (annealing near 250 °C) before final finishing on precision rings.
PTFE-C25 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| carbon powder (petroleum coke / carbon bwt%; some grades substitute 5% of it with graphite | 23 – 27 | 25 |
| PTFE (polytetrafluoroethylene)suspension/fine-cut PTFE moulding powder | ≥ 73 (balance) | — |
PTFE-C25 C25 — frequently asked
What is PTFE-C25 C25 used for?
PTFE-C25 C25 is typically used for compressor piston rings and rider bands, pump seals in oxidizer-free chemical service, bearings and bushings and valve packing. In short: highest-conductivity PTFE compound; dry-running compressor ring grade; avoid strong oxidizers.
What is the yield strength of PTFE-C25 C25?
PTFE-C25 C25 has a typical yield strength of 12 MPa (1.74 ksi) and a tensile strength of 15 MPa (2.18 ksi) — weaker than 88% of polymer grades. Strength varies by condition: see the 5 listed tempers.
Is PTFE-C25 C25 easy to machine?
Yes — machinability is rated very good (70/100, better than 74% of polymer grades). Turns and mills easily with sharp positive-rake carbide or PCD tools and light clamping; the coke filler is abrasive so tools dull faster than on virgin PTFE, and fine conductive dust needs extraction.
Can PTFE-C25 C25 be welded?
Not readily — weldability is rated not recommended (5/100). Cannot be fusion or solvent welded; join by mechanical clamping, bonding after sodium-etch/plasma surface activation, or by re-sintering in a mould.
What surface finishes work on PTFE-C25 C25?
Machined surfaces stay matte black and cannot be painted or plated without etching; deburr with sharp blades, and stress-relieve (annealing near 250 °C) before final finishing on precision rings.
Can PTFE-C25 C25 be formed, bent or molded?
Not melt-processable — preform is cold compression-moulded then free-sintered at ~370–380 °C with slow cool; ram extrusion is used for rod and tube, allow ~2–3% sinter shrinkage.
What is the maximum service temperature of PTFE-C25 C25?
PTFE-C25 C25 is rated for continuous use to about 260°C (500 °F), and briefly to 300°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between PTFE-C25 C25 and PTFE-C25 CB-ESD?
C25 is the default condition — default general-purpose carbon-filled PTFE for dry-running piston/guide rings, valve seats and hydraulic seals. CB-ESD: choose when only static dissipation is required and near-virgin mechanical properties must be kept. Yield strength is 12 MPa in C25 versus 10 MPa in CB-ESD.
Sources
- ASTM D4745 — Filled Compounds of PTFE Molding and Extrusion Materials — ASTM International (2021)
- ASTM D4894 — PTFE Granular Molding and Ram Extrusion Materials — ASTM International (2019)
- Filled PTFE compound datasheets (carbon, carbon/graphite grades) — Ensinger / Zeus / Chemours (Teflon design handbook) (2023)
- Engineered Materials Handbook Vol.2 — Engineering Plastics — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.