Chemical formula of polytetrafluoroethylene plate

-(CF2-CF2)n- belongs to the polymer: polytetrafluoroethylene (PTFE) relative molecular mass is large, low for hundreds of thousands, high for more than 10 million, generally millions (polymerization degree in the order of 104, and polyethylene only in 103). Generally, the crystallinity is 90 ~ 95%, and the melting temperature is 327 ~ 342℃. The CF2 units in the polytetrafluoroethylene molecule are arranged in a zigzag shape, and because the radius of the fluorine atoms is slightly larger than that of the hydrogen atoms, the adjacent CF2 units cannot be completely trans-cross oriented, but form a helical twisted chain, and the fluorine atoms almost cover the surface of the entire polymer chain. This molecular structure explains the various properties of teflon. When the temperature is lower than 19℃, 13/6 helix is formed. At 19 ° C, a phase transition occurs and the molecules unwind slightly, forming a 15/7 helix. Although the breaking of carbon-carbon bonds and carbon-fluorine bonds in perfluorocarbons requires 346.94 and 484.88kJ/mol, respectively, the depolymerization of PTFE to produce 1mol of tetrafluoroethylene requires only 171.38kJ of energy. Therefore, during pyrolysis at high temperature, polytetrafluoroethylene is mainly depolymerized to tetrafluoroethylene.