Huahao Sealing · Carbon Graphite Components
PTFE suffers severe creep causing seal-face pressure loss and leakage; carbon graphite is dimensionally stable. This article compares creep rate, thermal conductivity, temperature limit, hardness, and PV limit to guide chemical pump and compressor seal selection.
PTFE is known for its extremely low friction coefficient and near-universal corrosion resistance, but as a polymer its three key weaknesses — cold-flow creep, low thermal conductivity, and low hardness — become obvious in high-temperature, high-pressure seals: noticeable creep appears at 80–120°C, and seal-face pressure decay causes leakage. Carbon graphite offers dimensional stability, high thermal conductivity, and high hardness, delivering longer seal life under the same conditions. This comparison quantifies 8 key differences.
| Property | Carbon Graphite Seal | PTFE Seal |
|---|---|---|
| Creep rate (100°C/10MPa) | ≈0（无机物） | 1–3%/1000h |
| Thermal conductivity | 45–70 W/(m·K) | 0.25 W/(m·K) |
| Max service temperature | 500°C | 260°C |
| Hardness (Shore) | 78–82 HS | D50–D65 |
| PV limit (dry friction) | ×3–5 | ×1.0 |
| Dimensional stability | ✓ | ✗ (冷流) |
| Strong acid/alkali resistance | ✓ | ✓（更优） |
| Dry friction coefficient | 0.04–0.08 | 0.02–0.04 |
When seal service temperature exceeds 80°C or pressure exceeds 1 MPa, PTFE cold-flow creep causes seal-face pressure decay and leakage — carbon graphite should be preferred. Carbon graphite thermal conductivity is 180–280× that of PTFE, giving far superior heat dissipation, with a 3–5× higher PV limit, making it ideal for high-speed, high-pressure dry-friction seals. PTFE wins only in strongly oxidizing media (aqua regia, concentrated hydrogen peroxide) at temperatures below 80°C and pressures below 0.5 MPa in low-load service, thanks to superior corrosion resistance and lower friction coefficient.
PTFE is a semi-crystalline polymer; under sustained load its molecular chains slip and cold-flow, so seal-face pressure decays over time. At 100°C/10MPa the creep rate reaches 1–3% per 1000 hours, and once the face deforms the medium leaks along low-pressure zones.
Carbon graphite conducts 45–70 W/(m·K) vs only about 0.25 W/(m·K) for PTFE — a 180–280× difference. Frictional heat is dissipated quickly, preventing localized overheating and deformation of the seal face.
In strongly oxidizing media (aqua regia, concentrated hydrogen peroxide, concentrated nitric acid) at temperatures below 80°C and pressures below 0.5 MPa under low load. PTFE offers broader corrosion resistance and a lower friction coefficient (0.02–0.04).
Yes. Carbon graphite often serves as the rotating face while PTFE is used as a static seal ring or bellows, combining graphite wear/heat performance with PTFE corrosion-resistant compliance. However, as a friction pair, carbon graphite is typically mated with silicon carbide or tungsten carbide, not PTFE.
Contact our engineering team for technical specifications, custom solutions, or competitive quotes. We'll respond within 24 hours.
