Fluoropolymers melt-processable

Fluoropolymers. Melt processable fluoropolymers such as Teflon FEP, Tefzel ETFE, poly(vinylidene fluoride) (Kynar), and ethylene-chlorotrifluoroethylene copolymer (Halar) are suitable for wire insulation in special applications because they combine good physical properties with low flammability. They are used for instrumentation cable in process-control rooms, as well as for computer and aircraft wiring and in military applications. The... 

Properties are similar to those of PTFE, and PFA fluoropolymers are generally considered to be the best melt-processable alternative to PTFE yet available. They are, however, more expensive than PTFE. Compared with the TFE-FEP copolymers such as Teflon I P the PFA fluoropolymers ... 

FEP and PFA despite being melt-processible are crystalline (between 50 and 70%). The crystallinity results in poor optical properties (low clarity) and a very poor solubility in organic solvents. The latter makes the preparation of thin optical coatings exceedingly difficult.10 TEFLON AF, an amorphous fluoropolymer, contains in its molecule a bulky dioxole ring, which hinders crystallization. As a result, the polymer has an exceptionally high clarity and excellent optical properties. Its refractive index is the lowest of any plastic.11... 

Extrusion Guide for Melt Processible Fluoropolymers, Bulletin E-85783, E. I. Du Pont de Nemours Co., Wilmington, DE. 

Ebnesajjad, S., Fluoroplastics, Vol. 2, Melt Processible Fluoropolymers, Chapter 10, William Andrew Publishing, Norwich, NY, 2003. 

Summary of Properties of Selected Melt-Processible Fluoropolymers... 

Of the melt-processible fluoropolymers, which are the most suitable for tubing, PFA provides the extreme thermal and chemical resistance required in the pharmaceutical processing. PFA, however, does not have the physical strength of PTFE at elevated temperatures... 

Because of its high viscosity (10 °-10 poise at 380°C), PTFE cannot be fabricated by melt-processing techniques. Melt-processible fluoropolymers have been developed by copolymerization of TFE, and FEP, a copolymer of TFE and HFP, has a lower maximum continuous use temperature than PTFE (200° C vs. 260° C) because of the deterioration of mechanical properties. Whereas, PFA, a copolymer of TFE with PPVE or PEVE, offers thermal stability, melt-processibility, and a maximum continuous use temperature of 260°C. Both FEP and PFA are considered perfluoropolymers. 

With the exception of two fluoropolymers, PVF and PTFE, the rest of the resins described in this entry can be processed by standard melt-processing techniques, such as injection, transfer and blow molding, extrusion, and rotational molding. Process equipment for fluoropolymers must be made from corrosion resistant alloys because of the corrosive compound that may be produced when fluoropolymers are heated above their melting points. Higher melt viscosity of these resins may require more powder and higher pressure rating equipment. 

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