Except for molten alkali metals, PTFE air filter membranes are almost not corroded by any chemical reagents.
For example, when boiled in concentrated sulfuric acid, nitric acid, hydrochloric acid, or even aqua regia, its weight and performance remain unchanged. It is also almost insoluble in all solvents, and is only slightly soluble in peralkanes above 300°C (about 0.1g/100g ).
PTFE does not absorb moisture, is non-flammable, and is extremely stable to oxygen and ultraviolet rays, so it has excellent weather resistance.
Electrical properties PTFE air filter membrane has low dielectric constant and dielectric loss over a wide frequency range, and has high breakdown voltage, volume resistivity and arc resistance.
The radiation resistance of PTFE air filter membrane is poor (104 rad). It causes degradation after being exposed to high-energy radiation, and the electrical and mechanical properties of the polymer are significantly reduced.
Polymerized polytetrafluoroethylene is produced by free radical polymerization of tetrafluoroethylene.
Industrial polymerization reactions are carried out with stirring in the presence of a large amount of water to disperse the heat of reaction and facilitate temperature control.
Polymerization is generally carried out at 40-80°C and a pressure of 3-26 kgf/cm2. Inorganic persulfate and organic peroxide can be used as initiators, or a redox initiating system can be used.
Each mole of tetrafluoroethylene releases heat of 171.38kJ during polymerization.
Dispersion polymerization requires the addition of perfluorinated surfactants, such as perfluorooctanoic acid or its salts.
Application PTFE air filtration membrane can be formed by compression or extrusion processing; it can also be made into a water dispersion for coating, impregnation or fiber making.
PTFE air filtration membrane is widely used as high and low temperature resistant, corrosion resistant materials, insulation materials, and anti-stick coatings in atomic energy, aerospace, electronics, electrical, chemical, machinery, instrumentation, instrumentation, construction, textile, food and other industries. wait.
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