Structure and characteristics of PTFE

(1) In PTFE, the fluorine atom replaces the hydrogen atom in polyethylene, due to the large size of the fluorine atom with a radius of (0.064 nm), which is larger than the radius of the hydrogen atom (0.028 nm), and the negative charges of the fluorine atoms of adjacent macromolecules repel each other, making the C-C chain gradually reverse from the flat, fully extended zigzag conformation of polyethylene to the helical conformation of PTFE. The C-C chains gradually twist from the planar, fully extended zigzag conformation of polyethylene to the helical conformation of PTFE and form a tight, completely "fluorine substituted" protective layer, which gives it chemical stability and low cohesive energy density unmatched by other materials.

(2) The bond energy of C-C bond is 372kJ/mol, and the bond energy of C-F bond is 347kJ/mol, which is the stronger of the known bond energy, so the intramolecular bonding is strong and heat resistance is high, and the long-term use temperature is -250℃～260℃, while the bond length of C C-C bond length is 1.54 × 1010m, C-F bond length is 1.41 × 1010m, and is the shorter of the common single bond, so the chemical properties are stable, it is difficult to chemically react with other substances, showing excellent weather resistance, staining resistance and chemical resistance.

(3)There is no branched chain on the main chain of macromolecule, and no cross-chain is formed within the whole, so its molecular profile is smooth, plus the TFE monomer has perfect symmetry and the attraction and surface energy between PTFE molecules is low, so PTFE has very low surface friction coefficient, and it is easy to transfer to the counterpart surface to form a thin transfer film in the sliding process.