Introduction to More Common Fluoroplastics
We tend to forget that to many other people, they are unusual and very uncommon plastics. So here for the layman is a simple guide to what is what in the fluoroplastic world.
Fluoroplastics is a clumsy word given to a group of plastics where the molecules contain carbon and fluorine. The plastic polythene is a molecule consisting of a carbon chain with hydrogen atoms attached. PTFE is much the same but with the hydrogen atoms replaced with fluorine atoms. The replacement of the hydrogen atoms with fluorine atoms dramatically changes the properties of the material, and fluoroplastics therefore tend to have special properties:-
- Very high working temperatures.
- Non-stick characteristics.
- Very high resistance to chemical and solvents.
- Very high electrical resistance.
The more common members of the fluoroplastic family, with which we work, are:-
PTFE (Poly Tetra Fluoro Ethylene)
Trade names: Fluon, Hostaflon.
PTFE is the grandfather of all fluoroplastics, it is the most unusual and exhibits the best performance in terms of temperature and chemical resistance, and non-stick properties.
Its major disadvantage is that it does not actually melt when heated and therefore is difficult to process, and very unconventional techniques are needed to mould, extrude and weld it.
FEP (Fluoro Ethylene Propylene)
This is mainly manufactured by Chemours Co. and was developed as a ‘‘melt processable’’ version of PTFE. That is, it can be processed by normal plastic methods. It has basically similar properties to PTFE but a lower maximum operating temperature of 200°C instead of 260°C.
PFA (Per Fluor Alkoxy)
PFA was developed as a high temperature version of FEP, generally it has similar properties but it can be used at temperatures up to 260°C. It is very expensive!
ETFE (Ethylene Tetra Fluoro Ethylene Copolymer)
Trade Name: Tefzel Chemours developed this material as tough fluoroplastic. It is a normal thermoplastic but it is much harder than PTFE & FEP and similar in hardness to nylon, and is therefore used as an ‘‘Engineering Plastic’’. The improvement in stiffness is paid for by reduced chemical resistance and working temperature
E-CTFE (Ethylene-Chloro Tri Fluoro Ethylene)
Trade name: Halar A tough plastic with similar properties to Tefzel. Used mainly for its chemical resistance.
PVDF (Poly Vinylidene Fluoride)
Trade names: Kynar, Solef Very hard plastic roughly comparable to Halar and relatively cheap compared with other fluoroplastics. Good chemical resistance but not as good as C-TFE and ETFE.
PVF (Polyvinyl Fluoride)
Trade name: Tedlar Again a hard tough fluoroplastic with limited chemical and temperature resistance. Normally used as a film in gas bags, solar heating panels, printing circuit laminating, etc.
The above information is very general and we are very keen to discuss the properties of these materials and to select the best one for your application. There are many subtle differences in these plastics, which if chosen carefully can give very great price/performance benefits.