Polychlorotrifluoroethylene (PCTFE):
The main characteristics are:
- hard, stiff, unbreakable,
- transparent to opaque,
- no smell or taste,
- weather resistant,
- non-toxic thermoplastic even thin films are pore-free,
- bondable and weldable, easily machined.
1. The main difference in the property profiles of PTFE and PCTFE reflects their chemical structures.
2. The chlorine atom is significantly larger than the fluorine atom.
3. The absolutely symmetrical structure of the PTFE back bone is thus disturbed and the chain separation is enlarged.
4. Although the chain segments can still crystallize, this is much impeded and is thus less than PTFE.
5. Although the chain mobility is slightly increased, the polarity of the chlorine atom results in larger intermolecular forces and thus a stronger and stiffer polymer.
6. The polarity affects primarily the electrical properties of the polymer and limits its use to the high frequency range.
Availability:
1. PCTFE is thermoplastic and is supplied as granules primarily as a homopolymer for injection molding and extrusion.
2. Copolymers with vinylidene fluoride and other monomers are also available.
3. Powder grades are supplied for the manufacture of dispersions. Profiles, tubes, rods, blocks and films are available.
Thermal Properties:
1. The upper service temperature of 150°C is set not only by decreasing mechanical strength but also by embrittlement on long exposure to heat.
2. The polymer melts at 216°C and glass transition temperature is 45 °C.
Electrical Properties:
1. PCTFE's insulating properties are very good because it does not absorb water because of its thermoplastic character, even thin films are free from pores.
2. The dielectric properties are impaired by the dipole moment arising from the chlorine atoms. Other electrical properties are comparable with those of the perfluorinated polymers.
Optical Properties:
The refractive index n20D is 1.425. Rapid quenching of films and thin-walled moldings leads to crystal-clear transparency.
Permeability to Water Vapor & Gases:
PCTFE exhibits good barrier properties to gasses. PCTFE has the lowest permeability to water vapor of all transparent plastics films.
Chemical Properties
Resistance to Chemicals
1. Resistant to acids, alkaline solutions, many solvents at room temperature, aromatic or chlorinated hydrocarbons/esters and ketones cause reversible swelling of PCTFE at elevated temperatures.
2. It is not resistant to chlorosulfonic acid or molten alkali metals.
Weathering Resistance
PCTFE is weather resistant
Resistance to High Energy Radiation
Even small dosages of high energy radiation damage PCTFE similarly to PTFE. Because of the separation of chlorine, long exposure of PCTFE to radiation may result in corrosion of neighboring metal components.
Processing:
1. Preferred processing methods are compression molding, extrusion and injection molding.
2. Metallic substrates can be coated with the help of dispersions.
3. Injection molding melt temperature: 70 to 280°C
4. Mold temperature: 89 to 130°C. Shrinkage 1 to 2%
5. Extrusion melt temperature 290 to 300°C also for cable sheathing
6. Compression molding melt temperature 270 to 280°C
7. Copper cable must be nickel or silver plated prior to sheathing because copper- and iron containing alloys catalyze degradation of PCTFE. High frequency and ultrasonic welding are suitable, bonding requires pretreatment. Films can be laminated, thermoformed, hot sealed, printed and vacuum metallized.
Typical Applications
1. Crucibles, fittings, tubes, inspection ports, membranes, cable insulation, printed circuits, spool cores, insulating films and pharmaceutical packaging.
2. High frequency applications are limited.
Trade Names
Neoflon (Daikin America Inc., lP) Kel-F (3M Co., US)
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