Perfluoroether
Perfluoroalkoxy polymers ( PFA designation ) are fully fluorinated polymers, copolymers of tetrafluoroethylene ( TFE) and perfluoroalkoxy vinyl ethers, such as Perfluorvinylpropylether.
You are an evolution of the popular sintered material polytetrafluoroethylene (PTFE) and were first brought this as DuPont on the market. But PFA are melt-processable ( injection molding, extrusion, welding), in contrast to PTFE.
Major brand names for PFA Teflon ® PFA, Dyneon ® and Hyflon ®.
Properties
PFA has a low strength and hardness. It is resistant to almost all chemicals, shows a very high temperature resistance and flame retardant (UL 94 V -0). PFA has a low coefficient of friction, has a largely inert behavior, high sliding wear and extremely low adhesion.
- Usual processing temperatures: 380 ° C to 450 ° C.
- Melting point: about 310 ° C.
- Operating temperature: -200 ° C to 260 ° C
- Friction coefficient dyn dry: about 0.20-0.30
- Pronounced anti-adhesive behavior
- Low water absorption (< 0.03%)
- Low thermal conductivity
- Typical density: about 2.15 g / cm ³
Use
PFA is used in the element trace analysis to lower detection limits. The use of PFA vessel materials is best suited for it. Today in trace element analysis at concentrations in the ng / g ( ppb) is - and pg / g ( ppt) working area. Vessel materials of glass, quartz, polyethylene ( PE) and polypropylene ( PP) can cause interactions with the vessel wall with sample or reference solution concentration change and so distort analytical results.
Studies have shown that the durability is ensured by low-concentration element standards in vessels made of PFA over a very long time. The use of vessels made of PFA is not only from an analytical perspective safer, but also more economically through the rationalization of laboratory procedures.
Common uses for PFA is in addition to the use as a hose and fitting material for aggressive chemicals, corrosion- resistant lining in chemical plant. By the lining of components made of carbon steel or GRP it offers an alternative to nickel-based materials such as Hastelloy, Inconel or Monel. Typical applications in chemical plant, gas scrubbers, reactors, tanks, tubes and centrifuges. With PFA lined scrubbers are usually resistant to halogens.
In coal-fired power plants, it is found as a lining for heat exchangers. By the acid-resistant Rohgaseströme PFA can be cooled below the condensation point, without the heat exchanger is damaged. This allows an increase in the efficiency of a power plant can be achieved.
Other names are Perfluoralkoxy copolymer, perfluoroalkoxy and Perfluoralkoxy copolymer.