Kel-F is a fluorochemical product also known as PCTFE.
PCTFE offers an unique combination of physical and mechanical properties, nonflammability, chemical resistance, near zero moisture absorption and excellent electrical properties. These characteristics cannot be found in any other thermoplastic fluoropolymer (such as FEP and PFA) with a useful temperature range of -204°C to +204°C.
PCTFE also has an extremely low outgassing, it is well suited for use in aerospace and flight applications.
This material is milky-transparent with good chemical properties. It is used as an alternative to mica in level gauges, to protect transparent level gauge glass against aggressive mediums. Mica is standard, but in some situations mica will be affected. In those cases the more expensive and thicker Kel-F® is needed.
Note: Kel-F® is a registered trademark of 3M. 3M ended the manufacturing of Kel-F in 1996. Nowadays, PCTFE resin is manufactured by Daikin under the trade name Neoflon®, or by Allied Signal under the trade name Aclon®. Kel-F® is still the most widely used tradename to describe PCTFE.