Trade names "Teflon", "Teflon", "Teflon", "Teflon", "4F", etc., PTFE is a perfluoropolymer prepared by radical polymerization of tetrafluoroethylene. It has a linear molecular structure of -CF2-CF2- repeating unit and is a crystalline polymer with a melting point of approximately 631°F and a density of 2.13-2.19g/cm3. PTFE has excellent chemical resistance, its dielectric constant is 2.1, the loss factor is low, and it is stable in a wide temperature and frequency range. Its mechanical properties from low temperature to 550V are very good.
PTFE has high impact strength, but its tensile strength, wear resistance and creep resistance are worse than other engineering plastics. Sometimes glass fiber, bronze, carbon and graphite are added to improve its special mechanical properties. Its friction coefficient is lower than almost any other material, and it has a high oxygen index.
PTFE can be made into pellets, coagulated fine powder (0.2 microns) and water dispersion. Granular resin is used for compression molding and plunger extrusion; fine powder can be extruded as a paste to form thin-walled materials; dispersion can be used for coating and impregnating porous materials. The pure PTEE products distributed in the US market include AI-goflo brand of Auimont USA, Teflon brand of DU POut, FI brand of ICI AInericas Inc, and HOSaflon brand of HOechst Celanese.
PTFE has a very high melt viscosity, which prevents the adoption of conventional melt extrusion or molding techniques. The molding and extrusion methods of granular PTFE are similar to those used for powdered metals and ceramics. It is first compressed and then sintered at high temperature; the fine powder needs to be mixed with processing accessories (such as naphtha) to form a paste, and then extruded under high pressure into a thin The wall material is heated to remove volatile processing aids, and finally sintered.