Polytetrafluoroethylene (abbreviated as Teflon or [PTFE, F4]), known as/commonly known as "Plastic King", trade names "Teflon", "Teflon", "Teflon", "Teflon" ", "Teflon" and so on. It is a polymer compound formed by the polymerization of tetrafluoroethylene, with excellent chemical stability and corrosion resistance (it is one of the best corrosion resistance materials in the world today, in addition to molten metal sodium and liquid fluorine, it is resistant to other All chemicals do not change even when boiled in aqua regia, and are widely used in various applications that require resistance to acid, alkali and organic solvents), sealing, high lubrication and non-stick properties, electrical insulation, good anti-aging endurance, and excellent temperature resistance ( It can work for a long time at the temperature of +250℃ to -180℃). Teflon itself is not toxic to humans, but perfluorooctanoate (PFOA), one of the raw materials used in the production process, is thought to be potentially carcinogenic.
Its production solves many problems in chemical, petroleum, pharmaceutical and other fields. PTFE seals, gaskets, gaskets. PTFE seals, gaskets, and gaskets are made of suspension polymerized PTFE resin. Compared with other plastics, PTFE has the characteristics of chemical resistance and corrosion resistance, and it has been widely used as sealing material and filling material.
Used as engineering plastics, it can be made into PTFE pipes, rods, belts, plates, films, etc. It is generally used in corrosion-resistant pipelines, containers, pumps, valves, and radar, high-frequency communication equipment, and radio equipment with high performance requirements. The dispersion liquid can be used as insulating impregnating liquid for various materials and anti-corrosion coating on the surface of metal, glass, pottery, etc. Various PTFE rings, PTFE gaskets, PTFE packings, etc. are widely used in various types of anti-corrosion pipeline flange sealing. In addition, it can also be used for spinning, polytetrafluoroethylene fiber - fluorine (foreign trade name is Teflon).
At present, all kinds of PTFE products have played a pivotal role in the fields of national economy such as chemical industry, machinery, electronics, electrical appliances, military industry, aerospace, environmental protection and bridges.
Polytetrafluoroethylene (PTFE) molding technology PTFE mainly has the most common molding technologies such as molding, hydraulic pressure, pushing, extrusion, spraying, bonding, welding and winding. The first five are directly processed into products with PTFE resin, and the last three are processed into various products with PTFE plastic sheets or thin strips. In addition, there are other forming methods such as rolling method and thermoforming method. Now briefly introduce various molding methods.
Compression method Compression molding mostly uses suspended resin, and when the thickness of the sheet is less than 1.5mm, dispersion resin is used. The process: resin - sieving (suspended resin is smashed, loosened, and sieved through a 20-mesh sieve) - press (the PTFE powder loaded into the mold is compacted and formed by the press under the pressure of 20-235Mpa) - Sintering (sintering in a sintering furnace at a temperature of 370°C-380°C) - Molded products (after cooling and shaping in a mold or in a free state, it becomes the required plates, rods, tubes, gaskets and filler products, etc.).
Hydraulic method Hydraulic method, also known as equal pressure method or rubber bag method, is a special method of making PTFE products. It is to apply hydraulic pressure to the rubber bag to make the rubber bag expand the PTFE resin to the mold, so that it is compacted and then sintered into a product. The basic operation process is: put the rubber bag in the outer mold - connect the water pump, fill with tap water to make the rubber bag swell into a cylindrical shape - add resin evenly between the bag and the outer mold - close the mold - continue to fill with water and gradually increase the water When the pressure reaches 12-13Mpa, the pressure is maintained for 30 minutes, and then the water is released-decompressed, the mold is demolded, sintered, and cooled to form a prefabricated product with a smooth appearance.
2.3 Pushing method Pushing is also called paste extrusion molding. The 20-30 mesh sieved dispersing resin and organic liquid (toluene, petroleum ether, solvent oil, etc.) are prepared into a 1:5 paste mixture, which is pre-pressed into a The thick-walled cylindrical blank is put into the barrel of the pusher, heated, and pressed with a plunger to form. After drying, it is sintered at a temperature of 360-380 °C. After cooling, strong and tough push tubes, rods and other products are obtained. .
2.4 Extrusion method Extrusion molding can be divided into screw extrusion and plunger extrusion. The pre-sintered resin after crushing and screening is added to the barrel, and the raw material is compacted by the rotation of the screw or the reciprocating push of the plunger. It is transported to the extruder, and continuously extruded, sintered and cooled at a temperature of 360-400°C to form various tubes and rods.
2.5 Spraying method The spraying method has two processes: PTFE emulsion spraying and sintering film formation and PTFE resin powder plasma spraying directly to film formation.
2.6 Bonding method The bonding method is to use the treatment liquid to destroy the C-F chain on the surface of PTFE, so that the F atoms are separated, leaving carbon atoms so that the surface can be bonded to the substrate with an adhesive.
2.7 Welding method There are two welding methods, one is to use PFA electrode for hot air welding; the other is to use a certain temperature and pressure to heat two PTFE plates together.
2.8 Winding method Winding method is a new type of corrosion protection technology with its own characteristics developed for many years. Its characteristic is that it can process various complex components and occupies an important position in the current corrosion-resistant lining technology. This method is actually the same as the hot-press welding method, which relies on the control of temperature and pressure to fuse the PTFE together, but the difference is that the welding method is a single-layer local fusion, and the winding method is a multi-layer whole. Fusion bonding, the quality requirements of the latter are better than those of the former.
2.9 Rolling method Rolling molding can be divided into two processes: unidirectional rolling and multi-directional rolling. After rolling, the PTFE membrane turns from opaque white to translucent crystal color. One-way rolling is the process by which the reheated transparent film is rapidly passed through two identically rotating rolls of the calender. The calendering ratio is controlled within the range of 1.5-2.5, and the general roller speed is 20 rpm. Multi-direction rolling is a forming method in which the sintered and quenched diaphragm is placed on a calender and rolled in multiple directions to gradually reduce the film thickness. The rolling ratio is in the range of 2-2.5. The temperature of the drum should be controlled at 150-200℃, and the steam pressure should be 0.5-0.9MPa when the steam is heated. The calendering ratio is an important parameter, too large or too small is not good for the product. Sometimes it is necessary to repeat the rolling several times in order to press a piece of product.
2.10 Thermoforming Thermoforming is a method of using thermoplastic sheets as raw materials to manufacture plastic products. When manufacturing, the sheet cut into a certain size and fixed shape is first clamped on the frame and heated to a thermoelastic state, and then it is brought close to the surface of the mold by the applied pressure, thereby obtaining a shape similar to the surface. Sample. After the formed sheet is cooled, it can be taken out from the mold, and after proper trimming, it becomes a product. The applied pressure is mainly by the air pressure difference between the two sides of the sheet, but can also be by means of mechanical pressure or hydraulic pressure. There are six basic methods of thermoforming: differential pressure forming, overlay forming, plunger pressure-assisted forming, back suction forming, mold forming, and double-piece thermoforming.
Español
عربي ،
русский язык
Portugiesisch