The chemical element Fluor has the atomic number 9 and is a typical halogene element. In its elementary form it is a very reactive gas F2. Because it is so very reactive it is not stable in nature so that only exists in molecules combined with other elements.
Because of its reactive character fluor is also very hazardous for any living subject. All reactions with elementrary fluor are very reactive and spontanous.
On the other hand all compounds containing fluor are very stable and not reactive So polymers with a high amount of flour such as PTFE resist against almost any attack of solvents and acids. Also fluoride gases such as CF4 or SF6 are almost completely inert and do not take place in reactions.
As plasma is able to cause reactions of non reactive Fluor compounds, these compounds are very important for plasma processes.
Stimulated by plasma fluoride molecules may form radicals. Plasma is able to break the C-F-link. Due to this reactions CF4 and SF6 are very effective plasma etching gases, in particular applied for silizium etching where SiF4 results.
By such a cracking process Fluor-radicals can be cracked from PTFE. In a hydrogen plasma these radicals react to HF-gas. New molecules may be able to link to the unsuturated c-links of the PTFE. This is almost the only process to modify PTFE surfaces so that they can be bonded or coated.
On the other hand radicals can be formed from fluoride gases, which can connect to polymers. By such a process polymeric PTFE coatings can be produced. By applying a fluoride surface on the inside of containers they may become impermeable for aggressive liquids.