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Fluorinated Phosphoronitrile Rubber (PNF) – Aviation Fuel
Fluorinated phosphorus nitrile rubber
Fluorinated phosphonitrile rubber (PNF) is the abbreviation for fluoroalkoxy phosphonitrile elastomer. In 1965, H.R. Allcock reported a fluorinated phosphonitrile rubber containing double OCH2CF3 groups [; In 1968, Horizons Corporation in the United States developed fluorinated phosphonitrile rubber containing OCH2CF3 and OCH2C3F7 groups. In 1972, Firestone Corporation in the United States conducted pilot production, and in 1983, Firestone transferred this technology to Ethyl Corporation. Commercial production began in 1985, with the product name Ethel F.
A domestic unit has conducted systematic research on the trimer synthesis, ring opening polymerization, and rubber processing and application of PNF since 1971. However, based on the conditions at that time, PNF has not been applied in practice [15]. The preparation of fluorinated phosphonitrile rubber first involves the reaction of phosphorus pentachloride and ammonium chloride to synthesize chlorinated phosphonitrile trimer, which is then heated for ring opening polymerization and then reacted with fluoroalcohols to obtain PNF elastomer. The main chain of PNF is a repetitive nitrogen phosphorus bond (PN), and the fluoroalkoxy groups on the side chains not only provide good protection for the main chain and give it chemical stability, but also provide excellent flexibility for polymer molecules and excellent low-temperature performance. The glass transition temperature of the raw rubber is less than -60 ℃, and it can maintain elasticity at -65 ℃. Although the fluorine content of PNF is not high, only about 50%, due to its unique molecular structure, it still has excellent stability for aviation fuels, hydraulic oils, lubricants, and organic solvents, as well as good shock absorption and fatigue resistance. Under high temperature conditions, the retention rate of physical and mechanical properties such as tensile strength and elongation is also significantly better than other fluororubber and fluorosilicone rubber. The typical properties and 180 ℃ hot air aging performance of domestic fluorinated nitrile rubber are shown in Table 3, and the oil resistance performance is shown in Table 3