The relative molecular mass of polytetrafluoroethylene is large, the low is hundreds of thousands, the high is more than 10 million polytetrafluoroethylene, generally millions (the degree of polymerization is on the order of 104, while polyethylene is only 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.
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