PTFE (PTFE) with excellent resistance to high and low temperature performance and chemical stability, good electrical insulation performance, Non-stick, weatherability, flame-retardant and good self-lubricating, has been in the chemical industry, petroleum, textile, electronic and electrical, medical, mechanical and other fields have been widely used.
PTFE (PTFE) is the most consumed and widely used in fluorine plastics, and it is an important variety in fluorine plastics. PTFE has excellent resistance to high and low temperature performance and chemical stability, good electrical insulation performance, Non-stick, weatherability, flame-retardant and good self-lubricating, "Plastic King" laudatory name. The material was first developed for national defense and cutting-edge technical needs, and then gradually extended to civilian use in many aspects of aerospace and civilian applications, and is now an indispensable ingredient in its application.
PTFE is a polymer composed of tetrafluoroethylene monomers, a kind of transparent or opaque wax like PE, with a density of 2.2g/cm3, water absorption rate is less than 0.01%. Its chemical structure is similar to PE, except that all hydrogen atoms in polyethylene are replaced by fluorine atoms. Because the-key can be high, the performance is stable, thus its chemical resistance is excellent and can withstand all strong acids (including Aqua regia) except for molten alkali metals, fluorinated media, and sodium hydroxide above 300 ℃, as well as the effects of strongly oxidizing agents, reductant and various organic solvents; the F atom in the PTFE molecule is symmetric, The two elements in the-Bond are covalently bonded, the molecule has no free electrons, so the whole molecule is neutral, so it has excellent dielectric properties and its electrical insulation is not affected by the environment and frequency. Its volume resistance is greater than 1017 kin m, the dielectric loss is small, the breakdown voltage is high, the arc resistance is good, can in 250 ℃ electrical environment long-term work; because the PTFE molecule structure has no hydrogen bond, the structure is symmetrical, so its crystallinity is very high (general crystallinity is 55%~75%, sometimes up to 94%), make PTFE Excellent heat resistance, its melting temperature is 324 ℃, the decomposition temperature is 415 ℃, the maximum use temperature is 250 ℃, the embrittlement temperature is-190 ℃, the thermal deformation temperature (0.46MPa condition) is 120 ℃. The mechanical properties of PTFE are good, the tensile strength is 21~28mpa, the bending strength is 11~14mpa, the elongation is 250%~300%, and the friction coefficient of the steel is 0.04, which is smaller than that of nylon, pom and polyester plastic.
Use of PTFE
PTFE's unique properties make it widely used in the fields of chemical, petroleum, textile, food, papermaking, medical, electronic and mechanical industries and marine operations.
1, anti-corrosion performance of the application
Because of the defects in corrosion resistance of rubber, glass, metal alloy and other materials, it is difficult to meet the conditions of harsh temperature, pressure and chemical medium coexistence, the resulting loss is quite alarming. PTFE material with its excellent corrosion resistance, has become the oil, chemical, textile and other industries, the main corrosion-resistant materials. Its specific applications include: conveying corrosive gas pipe, exhaust pipe, steam pipe, rolling mill high-pressure tubing, aircraft hydraulic system and cold pressure system of high and low pressure pipeline, distillation column, heat exchanger, kettle, tower, trough lining, valves and other chemical equipment.
The performance of the seal has a great influence on the efficiency and performance of the whole machine equipment. PTFE materials with corrosion resistance, anti-aging, low friction coefficient and viscosity, wide range of temperature, good elasticity of the characteristics of the very suitable for the manufacture of corrosion-resistant requirements, the use of temperatures above 100 ℃ seals. such as machines, heat exchangers, high-pressure containers, large diameter containers, valves, pumps groove flange seals, glass reaction pot, flat flange, large diameter flange sealing parts, shafts, piston rods, valve rods, worm gear pumps, rod seals and so on.
2, low friction performance in the application of load
Due to the friction of some equipment is not suitable for refueling lubrication, for example, the lubrication grease will be dissolved in the solvent and the situation or paper, pharmaceutical, food, textile and other industrial products need to avoid contamination of lubricating oil, which makes the filling PTFE material to become mechanical equipment parts oil-free lubrication (direct bearing load) the most ideal material. This is because the friction coefficient of the material is the lowest of the known solid material. Its specific uses include the bearings for chemical equipment, papermaking machinery, agricultural machinery, used as piston rings, machine tool guides, guide rings, widely used in civil engineering construction of bridges, tunnels, steel trusses, large-scale chemical pipelines, storage tanks supporting slider, as well as bridge support and bridging swivel and so on.
3, electronic and electrical applications
PTFE material inherent low loss and small dielectric constant so that it can be made into enameled wire, for micro-motor, thermocouple, control devices, etc. PTFE film is the manufacture of capacitors, radio insulation gasket, insulated cable, motor and transformer ideal insulation material, aerospace and other industrial electronic components indispensable materials. The use of fluoride plastic film on oxygen permeability, the permeability of the water vapor is small, which can make the oxygen sensor, and the characteristics of the extreme charge deviating phenomenon in the high temperature and high pressure can be made by using fluorine plastics, and the parts such as microphone, loudspeaker and robot may be manufactured, and optical fiber can be made by using its low refractive index characteristics.