Polyvinyl fluoride (PVF) or –(CH2CHF)n– 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 the repeating vinyl fluoride unit: It is structurally very similar to polyvinyl chloride. PVF is also used as whiteboard surface material and has recently been used as part of the Phoenix Mars Lander's biobarrier.