PCTFE was discovered in 1934 by Fritz Schloffer and Otto Scherer who worked at IG Farben. PCTFE was commercialised under the trade name Kel-F 81 by M K Kellogg in the early 1950’s.
The actual Kel-F® product is no longer available in the marketplace but the name is still used widely in the industry, along with PTCFE.
PCTFE is a harder and stronger polymer, with better mechanical properties than PTFE. The crytallisability of PCTFE can be altered by controlling cooling in the melt processing operation; this feature is exploited to get various properties and applications. With high Crystallinity, PCTFE is dense with high mechanical properties and elongation. Alternatively, when quench-cooled, PCTFE is lighter, transparent, and more elastic making it suitable to be used in cryogenic engineering applications for handling liquid oxygen and liquid nitrogen. Valve seats made of PCTFE are widely used at cryogenic temperatures.
PCTFE has one of the highest limiting oxygen indexes. It has good chemical resistance and exhibits zero moisture absorption and non-wetting.
Its low coefficient of thermal expansion and its dimensional stability makes it attractive for use as a component of a structural part where the elevated temperature and chemical resistance of fluoropolymers are required.
Chemical Structure of PCTFE:
PCTFE, Kel- F® or Neoflon®, is a homopolymer of chlorotrifluoroethylene. The addition of a chlorine bond contributes to lowering the melt viscosity, which permits extrusion, compression moulding and injection moulding. It also contributes to the transparency, exceptional flow resistance and rigidity characteristics of the polymer. Fluorine is responsible for its chemical inertness and effectively zero moisture absorption.
Typical Material Properties:
| Material Property | Unit | Indicative Value |
|---|---|---|
| Mechanical Properties | ||
| Tensile Strength | MPa | 33.3 – 39.2 |
| Tensile Elongation at Break | % | 100 – 250 |
| Tensile Modulus of Elasticity | MPa | (1.2~1.4) x 104 |
| Density | g/cm3 | 2.10 – 2.18 |
| Impact strength | J/m | 133~144 |
| Shore Hardness | D | 75 – 90 |
| Thermal Properties | ||
| Melting Point | °C | 210~212 |
| Heat Deflection Temperature | °C | 126 |
| Specific Heat | 103J/Kg.K | 0.9 |
| Thermal Conductivity | W/m/k | 0.21 |
| Flammability | K – 1 | Non- flammable |
| Electrical Properties | ||
| Dielectric Constant at 103Hz | 2.6 | |
| Dielectric Dissipation Factor 103Hz | 0.02 | |
| Dielectric Strength Short time 4 mils thickness 68 mils thickness | kV/mm | 3000 500 |
| Volume Resistivity 50% R.H. | Ω-cm | 2 x 1017 |
| Surface Resistance 100% R.H. | Ω-cm | 1 x 1015 |
Typical PCTFE Processing Methods:
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- Injection moulding
- Extrusion
- Compression moulding
- CNC Machining
- Injection moulding
Because of its high melt temperature, PCTFE provides excellent machining characteristics for sawing, turning, drilling, milling, and cutting.
Unique Properties of PCTFE:
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- Cryogenic applications
- Excellent resistance to cold flow
- Good transparency
- Dimensional stability through a wide temperature range
- Extremely low moisture absorption
- FDA Approved
- Rigidity
- Extremely low gas permeability
Limitations of PCTFE:
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- The melting point is lower than for PTFE
- PCTFE rates lower than PTFE as a non-stick material
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