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Classification and application of polytetrafluoroethylene

Classification and application of polytetrafluoroethylene


PTFE resin is mostly in powder form or dispersion.


PTFE powder resin is a white, odorless, tasteless and non-toxic powder. When processed into products, it becomes a transparent or opaque white material, waxy, non-hydrophilic, smooth and non-sticky, and looks like polyethylene. Its density is as high as 2.14g/m3, making it the heaviest plastic.


There are three main categories of polytetrafluoroethylene: suspension resin, dispersion resin and concentrated dispersion. In my country, suspension resin accounts for approximately 66.81% and dispersion resin accounts for 31.19%.


4.1 Application of suspension polytetrafluoroethylene


Suspension PTFE is mainly used to manufacture sealing rings, gaskets, etc. for the machinery industry, as well as pumps, valves, pipe fittings, and equipment linings for chemical equipment. It also manufactures electrical insulation parts, films, etc.


Suspension PTFE is generally divided into the following three categories:


(1) Micro powder:


The average diameter of the particles is 20~35μm, which can be molded.


(2) Granulating materials:


It has good powder flowability and large apparent density. Coarse particles (particle size about 300 μm) are used for automatic molding and hydraulic molding, and can also be used for general molding.


(3) Pre-sintered material:


The plunger method can be used to process finer and thinner products. Such as rods with a diameter of 5~50mm, pipes with a wall thickness of 3~25mm, etc.


In addition, the suspension method PTFE can also be processed into ultra-fine-grained powder with a fineness of less than 10 μm. DLX-6000 from DuPont Mitsui Fluorochemicals Co., Ltd. and L-168, L-169, L-170 and L-171 from Asahi Glass Co., Ltd. are such products. Their main use is as dry powder lubricants. Currently, this type of resin is increasingly expanding its application scope as its properties are continuously improved and improved.


4.2 Application of dispersion polytetrafluoroethylene


Dispersion method PTFE is mainly used to manufacture corrosion-resistant, high-temperature-resistant, high-dielectric wires and cables. In the chemical industry, it is mainly used to manufacture threaded sealing tapes, pipe linings, etc.


(1) High compression ratio powder:


Extrusion molding under the condition of compression ratio greater than 2500:1, suitable for processing into thin-walled thin tubes and wire insulation sheaths with a diameter of less than 2mm and a wall thickness of 0.2~0.5mm.


(2) Medium compression ratio powder:


Extruded under the condition that the compression ratio is greater than 400:1, it is suitable for processing into medium-sized thin-walled tubes with a diameter of 2 to 15mm and a wall thickness of 0.5mm or more.


(3) Low compression ratio powder:


It is extruded under the condition that the compression ratio is less than 300:1, and is suitable for processing into thicker pipes and thick bars with a diameter of more than 5mm for making sealing raw material belts.


4.3 Application of PTFE concentrated dispersion


PTFE concentrated dispersion is mainly used as anti-stick coating and impregnated glass cloth, asbestos, etc. in the food, textile, printing and dyeing, papermaking and other industries.


In addition, it can also be used for fiberglass and porous materials.


4.4 Overview of classification of polytetrafluoroethylene products


(1) Polytetrafluoroethylene pipes: can produce micro thin-walled capillary tubes, push tubes, plunger extrusion tubes, etc. At present, the maximum diameter of domestic plunger extrusion pipe is 320mm, and the length is 4 to 6m.


(2) Polytetrafluoroethylene sheet: The maximum area of the molded sheet can reach 1.2×1.2m2. Turning plate: turning with isobaric forming blank, the plate width can be up to 2m, using molding forming blank, the plate width is 1.5m.


(3) PTFE rods: various general-purpose rods can be produced. The length of molded rods can reach 1.5m, isobaric molding can reach 2m, and plunger extrusion can reach 4~6m.


(4) Polytetrafluoroethylene film: PTFE film includes oriented film, non-oriented film, and semi-oriented film. At present, the widest domestic film can reach 600mm.


(5) PTFE-impregnated glass cloth: Due to limitations of the base material (glass cloth) and equipment, PTFE-impregnated glass cloth can currently only produce products with a width of 1.5m. At the same time, PTFE-impregnated glass cloth that can be bonded can also be produced.


(6) Expanded PTFE rib sealing tape: PTFE rib sealing tape has a thickness of 0.075~0.1mm and a width of 13, 22, 26, 52mm and other specifications. Many domestic units can produce it and export it in large quantities.


(7) Biaxially stretched PTFE microporous membrane and its composite materials: PTFE microporous membrane can be used as a filter material for the filtration of ultra-pure reagents, with a pore size of 0.1 to 1 μm; it can also be combined with fabric to make high-grade waterproof and breathable membranes. Clothing fabrics and high temperature resistant filter materials. The composite material width is up to 2m.


(8) Expanded PTFE sealing tape, packing, and filler rods: used as sealing materials in chemical anti-corrosion and other aspects. The operating temperature is -218~320℃; among them, the thickness of the sealing tape is 0.5~5mm, and the maximum width is 80mm. The diameter of the filler rod is 1~25mm.


(9) Polytetrafluoroethylene fiber: Fabrics made of PTFE fiber are used as filter materials abroad, and PTFE fiber and fabric samples are available in China.


(10) Polytetrafluoroethylene filled modified products: In order to improve the creep characteristics and wear resistance of PTFE, PTFE is filled and modified. The main materials include graphite, carbon black, molybdenum disulfide, glass fiber, carbon fiber, polyethylene Phenyl sulfide etc.


(11) Polytetrafluoroethylene corrugated pipes and reinforced pipes: corrugated pipes and fiber or steel wire braided reinforced hoses made by secondary processing, with high and low temperature resistance, pressure resistance, anti-corrosion, non-stick and long service life, etc. Features. Suitable for hose connections for hydraulic, pneumatic, steam delivery, etc.


(12) Fluorine-containing plastic coating and plating:


1. Fluorine-containing plastic coating: Fluorine-containing plastic coating has many characteristics of fluorine-containing plastic, mainly including anti-stick coating, anti-corrosion coating, sound insulating coating, noise reduction, hydrophobic and oleophobic coating. Widely used in aerospace, aviation, papermaking, petrochemical industry, light industrial machinery, medical and health care, food machinery, ships, etc.


2. Fluorine-containing plastic electroless plating: PTFE particles are plated onto the surface of the metal substrate during the nickel plating process through electroless plating. The thickness of the coating is 5 to 25 μm, and the surface hardness (HV) is 150 to 150 for untreated ones. 250; after heat treatment, it is 300~400. The coating does not fall off or peel off, is self-lubricating, and has a friction coefficient below 0.25.


4.5 Application fields of polytetrafluoroethylene


PTFE is the heaviest type of plastic. It has a wide operating temperature range (-250~260℃), good chemical stability, excellent dielectric properties, self-lubricating and anti-sticking properties, so it has a wide range of applications.


In the chemical industry, it can be used as anti-corrosion materials and can be used to manufacture various anti-corrosion parts, such as pipes, valves, pumps and pipe fittings, etc. In terms of chemical equipment, it can produce linings and coatings for reactors, distillation towers and anti-corrosion equipment.


Mechanically, it can be used as self-lubricating bearings, piston rings, oil seals and sealing rings, etc. Self-lubricating properties can reduce wear and heat of machine parts and reduce power consumption.


In terms of electronic appliances, it is mainly used to manufacture various wires and cables, battery electrodes, battery separators, printed circuit boards, etc.


Among medical materials, it can be used as a material for various medical devices and artificial organs by taking advantage of its heat-resistant, water-resistant, and non-toxic properties. The former include sterile filters, beakers, and artificial heart and lung devices, while the latter include artificial blood vessels, hearts, and esophagus.


Compared with other plastics, PTFE is chemically resistant and has been widely used as sealing and filling materials.


PTFE is used as engineering plastics and can be made into PTFE tubes, rods, strips, plates, films, etc. It is generally used in corrosion-resistant pipes, containers, pumps, valves, radars, high-frequency communication equipment, radio equipment, etc. that require high performance. The dispersion can be used as an insulating impregnation liquid for various materials and as an anti-corrosion coating on the surfaces of metal, glass, and ceramics. Various PTFE rings, PTFE gaskets, PTFE packing, etc. are widely used in various types of anti-corrosion pipeline flange seals. In addition, it can also be used for spinning polytetrafluoroethylene fiber - fluoronon (foreign trade name is Teflon).


At present, various types of PTFE products have played a decisive role in the national economic fields such as chemical industry, machinery, electronics, electrical appliances, military industry, aerospace, environmental protection and bridges.

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