Polyvinyl fluoride (PVF) or –(CH<sub>2</sub>CHF)<sub>n</sub>– is a polymer material mainly used in the flammability-lowering coatings of airplane interiors and photovoltaic module backsheets. It is also used in raincoats and metal sheeting. Polyvinyl fluoride is a thermoplastic fluoropolymer with a repeating vinyl fluoride unit, and it is structurally very similar to polyvinyl chloride.
History
The PVF-based film was first commercialised in 1961 by DuPont under the name Tedlar.
Polymerization
The most widely used polymerizations of VF are in aqueous suspensions or emulsions. High pressures are required because of the VF volatility. The high electronegativity of fluorine makes the polymerization more difficult when compared to other vinyl halides.
Properties
The majority of linkages in PVF are head-to-tail, and only 12-18 % of linkages are head-to-head. These irregularities are probably the cause of the variations in melting point, which ranges from 185 °C to 210 °C. The crystallinity of PVF ranges from 20 to 60%, depending on the polymerization method and thermal history of the polymer. It has been found that lower polymerization temperature leads to a decrease in head-to-head linkages and subsequently increase in melting point since the highly regular structures display higher crystallinity. As for stereoregularity, PVF is mostly atacic, but this does not significantly affect the melting point. The commercial atactic PVF film shows a melting point peak at 190 °C.
PVF is insoluble in common solvents below 100 °C. When the temperature is raised, it becomes soluble in polar solvents (amides, ketones etc.). At room temperature, the PVF films are resistant to both acids and bases as well as aliphatic, aromatic and alcohol liquids.
The monomer, VF is flammable and highly reactive, forms an explosive mixture with air and is classified as "probably carcinogenic to humans".