PCTFE
A stiff fluoropolymer for cryogenic valves
Typical values for the temper in the title
PCTFE (trade names Kel-F, Neoflon) is a fluoropolymer in which a chlorine atom replaces one of the fluorines. The result: a stiff, strong and far more dimensionally stable material than PTFE, with low creep and very low permeability to gases and water vapor. Its melting point is about 210 °C.
Its standout property is retaining properties at cryogenic temperatures, so it is used for valve seats and seals in liquid oxygen and hydrogen, and lab and space equipment. It machines well to tight tolerances.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 34–41 MPa | |
| Density ρ | 2.10 g/cm³ | |
| Max continuous service temperature | ≈120–150°C | |
| Machinability | 75% | relative rating in the site database |
Structure and family
| Feature | Value | Meaning |
|---|---|---|
| Family | chlorinated fluoropolymer | |
| Tm | about 210 °C | |
| Permeability | very low to gases |
Typical values per producer data sheets.
Grades and versions
In fluoropolymers the choice is by service temperature, processing route (melt or sinter) and strength. All are highly chemically resistant.
| Version | Properties | When to choose it |
|---|---|---|
| Rod and plate for machining | dimensionally stable | valve seats |
| Film | moisture barrier | pharmaceutical packaging |
Applications
- Cryogenic valve seats
- Liquid oxygen and hydrogen seals
- Laboratory equipment
- Space parts
- Pharmaceutical packaging
Fabrication
Machining
Use very sharp tools, a feed that does not overheat the material, and good support (the material is flexible and deforms under clamping). For precision parts, stress-relief annealing before final machining is sometimes performed.
Thermal expansion
The expansion coefficient of an unfilled polymer is several times that of a metal. In a precision part or an assembly with metal, design clearances accordingly.
Machining
Machines to tight tolerances better than PTFE, thanks to its stiffness.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| PTFE | 25 MPa | Sintering only | PTFE: soft, creeps, more heat resistant · material page |
| PVDF | 50 MPa | Hot Gas / Ultrasonic | PVDF: another fluoropolymer, cheaper · material page |
| PEEK | 100 MPa | Ultrasonic / Laser | PEEK: much stronger, not especially cryogenic · material page |
Common mistakes
Using it above about 150 °C
Its service temperature is lower than PTFE.
Choosing PTFE for a cryogenic valve seat
PTFE creeps. PCTFE is more stable.
Ignoring cost
It is expensive.
Equivalents, standards and supply
| ASTM | D1430 |
|---|---|
| Standards | ASTM D1430 |
| Forms | sheet · rod · pellets |
| Producers | Daikin (Neoflon) · Honeywell |
Learn more
Values are typical for an unfilled grade (unless stated otherwise) and for comparison only. In polymers, properties depend on grade, filler, temperature, moisture and load duration. For design, rely on the producer data sheet for the specific grade. Sources: ASTM classification standards (D8033, D5205, D5204, D6394, D4067 and others), producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026