What is PTFE K15?
PTFE K15 consists of a PTFE matrix (polytetrafluoroethylene) with 15 percent by weight of carbon or graphite filler. PTFE is a semi-crystalline fluoropolymer that is not melt-flowable and, like virgin PTFE, is therefore only machined, not welded. The embedded carbon/graphite content improves compressive and wear resistance, further lowers the coefficient of friction, and increases electrical conductivity compared with virgin PTFE, which is otherwise an excellent insulator. The colour is consistently black.
Unlike glass-fibre-filled PTFE (e.g. PTFE GF15, PTFE GF25), carbon/graphite filler barely affects chemical resistance – resistance to hydrofluoric acid, which limits glass-fibre-filled PTFE, is largely retained in K15. Carbon/graphite filler is also significantly less abrasive to soft counter-surfaces such as bronze or aluminium than glass fibre, which also sets K15 apart from the bronze-filled grades PTFE Bronze40 and PTFE Bronze60: bronze filler mainly raises compressive strength and thermal conductivity against metal counter-surfaces, while carbon/graphite lowers friction and creates moderate electrical conductivity without limiting chemical resistance.
At this filler level, K15 is still only weakly conductive to insulating (volume resistivity 10¹⁰–10¹¹ Ω·cm) – for reliably antistatic or conductive applications, the more heavily filled K25 is usually the safer choice. Chemically, K15 is near-universally resistant, including largely resistant to hydrofluoric acid; limits exist with fluorine and molten alkali metals.
Typical applications include plain bearings, slide strips and guide elements with moderate wear loading, seals and piston rings with reduced cold flow, and chemically loaded sliding and sealing parts up to 260 °C, including hydrofluoric acid contact. Typical industries are sealing technology, chemical process and plant engineering, pump and valve technology, compressor and drive technology, and electronics and semiconductor manufacturing.
Technical Data
| Property | Value | Test Standard |
|---|---|---|
| Physical Properties | ||
| Density | 2.15 g/cm³ | ISO 1183 |
| Water absorption | < 0.05 % | ISO 62 |
| Color | black | – |
| Mechanical Properties | ||
| Tensile strength | ≥ 14 MPa | ISO 527 |
| Elongation at break | ≥ 115 % | ISO 527 |
| Hardness | 58–62 Shore D | ISO 868 |
| Coefficient of friction (vs. steel) | ~ 0.15 | DIN 53375 |
| Thermal Properties | ||
| Service temperature | -200 to +260 °C | – |
| Coefficient of linear expansion (25–200 °C) | ≈ 10 · 10⁻⁵/K | DIN 52612 |
| Thermal conductivity | ≈ 0.45 W/(m·K) | DIN 52612 |
| Electrical Properties | ||
| Dielectric strength | ~ 5 kV/mm | IEC 60243-1 |
| Volume resistivity | ~ 10¹⁰ … 10¹¹ Ω·cm | IEC 60093 |
| Fire Behaviour | ||
| Flammability | V-0 (non-flammable) | UL 94 |
PTFE K15 in detail
1What is PTFE K15?+
PTFE K15 is a PTFE (polytetrafluoroethylene) filled with 15 % carbon/graphite. The filler noticeably improves wear resistance, cold flow and friction behaviour compared with virgin PTFE and also makes the material more electrically conductive, without significantly limiting the near-universal chemical resistance typical of PTFE. K15 is a balanced intermediate grade between virgin PTFE and more heavily filled compounds such as K25.
2How does Liedtke machine PTFE K15?+
PTFE K15 machines well – turning, milling, drilling and sawing all give clean results. Because the carbon/graphite dust is electrically conductive, we consistently ensure dust extraction and avoid deposits in the machine area; overheating is avoided throughout, since PTFE is not meltable or weldable.
3When should I choose PTFE K15?+
PTFE K15 is worthwhile when the benefits of PTFE need to be combined with better wear resistance and some electrical dissipative capability, without giving up as much toughness as possible:
- Plain bearings, slide strips and guide elements with moderate wear loading
- Seals and piston rings where cold flow needs to be reduced
- Applications with a light requirement for electrical dissipation
- Chemically loaded sliding and sealing parts up to 260 °C, including hydrofluoric acid contact
- Components where lower abrasiveness to the counter-surface is needed compared with glass-fibre compounds
4What determines the price of a PTFE K15 part?+
PTFE materials are among the higher-priced engineering plastics; carbon/graphite-filled grades such as K15 are in the range of virgin PTFE or slightly below. The component price is mainly determined by the semi-finished form and dimensions, material utilisation, machining effort and batch size. We are happy to provide binding prices on request based on your drawing.
5When is PTFE K15 not the right choice?+
For reliably defined, low electrical dissipation resistance (ESD requirements) or maximum wear resistance under sustained high load, the more heavily filled PTFE K25 is the more reliable choice. For unambiguous food contact without evidence, virgin/FDA-compliant PTFE is better suited, and joining by welding is not possible with PTFE at all.
6Advantages and disadvantages of PTFE K15+
An honest assessment:
- Advantage: Higher wear and compressive resistance than virgin PTFE
- Advantage: Reduced creep (cold flow) under sustained load
- Advantage: Very low friction coefficient, self-lubricating
- Advantage: More electrically conductive than virgin PTFE, good heat dissipation
- Advantage: Near-universal chemical resistance including hydrofluoric acid retained
- Disadvantage: Lower elongation/toughness than virgin PTFE
- Disadvantage: Electrical conductivity at 15 % not yet reliable enough for ESD requirements
- Disadvantage: Filled grade, food contact only with evidence
- Disadvantage: Not meltable/weldable (machining only)
- Disadvantage: Higher price than standard plastics
Typical Properties
- Higher wear and compressive resistance than virgin PTFE
- Reduced creep (cold flow)
- -200 to +260 °C, non-flammable (UL 94 V-0)
- Near-universal chemical resistance, including hydrofluoric acid
- Very low friction coefficient, self-lubricating
- Weakly conductive to insulating
- Colour black
- Machining only (not weldable)
Typical Industries
- Sealing technology
- Chemical process and plant engineering
- Pump and valve technology
- Compressor and drive technology
- Mechanical engineering (plain bearings)
- Electronics and semiconductor manufacturing
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