The weight loss rate (%) of the polytetrafluoroethylene sheets at 260, 370, and 420 ° C was 1 × 10 -4 , 4 × 10 - 3 , and 9 × 10 - 2 , respectively. It can be seen that the Teflon plate can be used at 260 ° C for a long time. Due to the high-temperature cracking, it also produces highly toxic by-products such as fluorophosgene and perfluoroisobutylene. Therefore, special attention should be paid to safety protection and to prevent exposure of PTFE to open flames. Mechanical properties Its friction coefficient is extremely small, only 1/5 of polyethylene, which is an important feature of the perfluorocarbon surface. Moreover, since the intermolecular force of the fluorine-carbon chain is extremely low, the polytetrafluoroethylene has no stickiness. Polytetrafluoroethylene maintains excellent mechanical properties in a wide temperature range of -196 to 260 ° C. One of the characteristics of perfluorocarbon polymers is that they are not brittle at low temperatures. Chemical and Weather Resistance In addition to molten alkali metals, PTFE is virtually free of any chemical attack. For example, in concentrated sulfuric acid, nitric acid, hydrochloric acid, or even boiling in aqua regia, there is no change in weight and performance, and it is almost insoluble in all solvents, and is slightly soluble in per-alkane (about 0.1 g/100 g) only above 300 °C. PTFE does not absorb moisture, is non-combustible, and is extremely stable to oxygen and ultraviolet rays, so it has excellent weather resistance. Electrical Properties Polytetrafluoroethylene has low dielectric constant and dielectric loss over a wide frequency range, and high breakdown voltage, volume resistivity, and arc resistance. Teflon plate radiation resistance Teflon has poor radiation resistance (104 rad), which is degraded by high-energy radiation, and the electrical and mechanical properties of the polymer are significantly reduced. Polymerization Polytetrafluoroethylene is produced by radical polymerization of tetrafluoroethylene. The industrial polymerization is carried out by stirring in the presence of a large amount of water to disperse the heat of reaction and to facilitate temperature control. The polymerization is generally carried out at 40 to 80 ° C under a pressure of 3 to 26 kgf/cm 2 , and an inorganic persulfate or an organic peroxide may be used as an initiator, or a redox initiation system may also be used. An exotherm of 171.38 kJ per mole of tetrafluoroethylene was polymerized. Dispersion polymerization must be added with perfluorinated surfactants, such as perfluorooctanoic acid or its salts. Forming shrinkage: 3.1-5.0% Molding temperature: 330-380 °C. PTFE plate sintering conditions: the best temperature should not exceed 385 degrees, otherwise The molecules will be necrotic and affect the quality. Material properties Long-term use temperature -200--260 degrees, excellent chemical resistance, corrosion resistance to all chemicals, friction coefficient is the lowest in plastic, and good electrical properties, its electrical insulation is not affected by temperature The impact, known as the "plastic king." It is transparent or translucent, and the higher the crystallinity, the worse the transparency.