By comparing the performance of PTFE and other plastics, this article points out the problems in the application of PTFE in mechanical engineering and introduces the modified PTFE filled in sliding guide rails, friction parts, seals, anti-corrosive parts, construction materials, agricultural machinery materials, and other applications, and prospects for new machinery applications. By comparing the performance of PTFE and other plastics, this article points out the problems in the application of PTFE in mechanical engineering and introduces the modified PTFE filled in sliding guide rails, friction parts, seals, anti-corrosive parts, construction materials, agricultural machinery materials, and other applications, and prospects for new machinery applications.

By comparing the performance of PTFE and other plastics, this article points out the problems in the application of PTFE in mechanical engineering and introduces the modified PTFE filled in sliding guide rails, friction parts, seals, anti-corrosive parts, construction materials, agricultural machinery materials, and other applications, and prospects for new machinery applications.

PTFE resin was first developed by the American chemist Dr. Plunket in 1938, and industrialized production was achieved abroad in the 1950s. my country was officially put into production in the 1960s. PTFE is commonly known as “King of Plastics”, and is widely used in various aspects for its unique properties. It has high-temperature resistance, non-oxidation, insolubility, particularly good chemical stability, and extremely excellent dielectric properties, making it one of the indispensable important materials for almost all industrial sectors mainly in the chemical and mechanical industries.

1. Self-lubricity

The friction coefficient of PTFE is smaller than other engineering plastics. It is the lowest friction coefficient among the known practical sliding surface materials. It is an ideal lubricating material.

2. Chemical resistance

Because PTFE has no double bonds and branched chains in its molecular structure and high crystallization, it has excellent chemical resistance and is the best among known engineering plastics. It does not interact with concentrated acids, dilute acids, concentrated alkalies, and strong oxidants even in high-temperature environments. It will not be corroded even if it is boiled, and it has no effect with most solvents such as alcohols, either and ketones.

3. Water absorption

PTFE has a very low water absorption rate, which is equivalent to UHMWPE and does not swell in water.

4. Wide range of high and low temperature

PTFE can be used continuously for a long time within a range of 200% to 260%. Even under a low temperature of 200℃, it is not brittle, and it can maintain a certain degree of flexibility.

5. Not sticky

PTFE is a solid material with the smallest surface energy at present. The surface tension is only 0.019N/m. Almost all solid materials cannot adhere to its surface.

6. Wear resistance

Pure Teflon is not very wear-resistant, but the addition of various fillers to Teflon improves the wear resistance dramatically, and it is more wear-resistant than some materials commonly used as friction parts (such as cast iron and copper).

7. Hygienic and non-toxic

PTFE is hygienic and non-toxic, meets hygienic standards, and can contact food and medicine.

8. Excellent electrical insulation performance

PTFE is a highly non-polar material with excellent dielectric properties, its breakdown voltage is 25-40KV/mm; the resistance is extremely large, and the volume-specific resistance is still as high as 1061~ at 200.

9. Completely non-combustible

The melting point of PTFE is 327, which is higher than other general polymers. At 260%, its breaking strength remains 5 MPa (about 1/5 of room temperature), and its flexural strength reaches 1.4 MPa. It has extremely valuable non-combustibility, its limited oxygen index is above 95, it can only be melted on the flame, no droplets are formed, and eventually, it is only carbonized.

10.Excellent aging resistance and radiation resistance

PTFE is not only dimensionally stable at low and high temperatures, but its performance also is unchanged under harsh environments, and it is not attacked by microorganisms in a humid state, and it has high protection against various radiations.

11. Other properties

PTFE has low hardness and soft texture, and has the ability to absorb and contain foreign materials, it is easy to process.

1. The purpose and method of modification

Although PTFE has many excellent characteristics, it also has many shortcomings. Compared with other engineering plastics, its mechanical properties are not very good; the coefficient of linear expansion is large; the molding shrinkage rate is large, and the secondary processing is difficult; the hardness is low and wear-resistant poor performance; poor creep resistance, easy cold flow; poor thermal conductivity and higher prices. These defects limit its wide application to a certain extent. The purpose of the modification is to improve mechanical properties; improve wear resistance; reduce linear expansion; enhance fluidity, etc.

2. Types and functions of filler modifiers

Filling and modifying PTFE with glass fiber, graphite, molybdenum disulfide, silicon dioxide, aluminum oxide, bronze powder, carbon fiber, etc. can improve its surface hardness, wear resistance, creep resistance, bending strength, resistance Comprehensive strength and dimensional stability. The hardness of PTFE compounded by glass fiber can generally be increased by 10%, and the wear resistance can be increased by more than 500 times. The creep resistance and cold flow resistance are greatly improved and improved; the addition of molybdenum disulfide helps The hardness and rigidity of PTFE products are improved, and the initial wear is reduced; PTFE filled with graphite has excellent chemical resistance, compression creep, and better thermal conductivity; PTFE filled with copper powder can improve the creep resistance of products defenestration, comprehensive strength, hardness, and dimensional stability.

1. Slide rail

Sliding guides are often the basis for the installation of metal cutting machine tools, medical instruments, and many other systems and devices, the basis of accuracy and the basis of positioning, or the sign of the life of these machines, and are an important part of the machine. In the machine tool manufacturing industry, most machine tool guide rail pairs are cast iron-cast iron, cast iron-quenched cast iron, cast iron-quenched steel, etc. However, due to its physical properties, the coefficient of friction between metals is large, it is not wear-resistant, it cannot work under dry friction, and crawls at low speeds and small displacements. This crawling will affect the feed accuracy and precision of machine tools, especially precision machine tools. Dependability. When the filled PTFE guide is used, the low-speed stability of the machine tool is greatly improved. Because the plastic guide rail has the characteristics of buried foreign objects, iron filings and sand particles can be embedded in the plastic to avoid its own wear and tear, prevent the drawing and scratching of the metal surface, and can protect the bed guide rail. PTFE containing bronze powder and other fillers has excellent friction properties. After the transfer film is formed on the metal surface, the friction coefficient is greatly reduced, the bearing capacity of the transfer film is greatly improved, and the effective working life is also extended. If it is matched with a metal machine tool guide, its friction coefficient remains constant as the sliding speed increases. Therefore, this kind of filled PTFE guide rail will not produce crawling phenomena at low speed and micro feed, and it also has vibration absorption and cushioning performance. The friction coefficient of the PTFE guide rail is 0.05 when dry friction, and 0.03 when there is oil lubrication, regardless of whether the machine tool guide rail has lubricating oil or not, its work movement is as smooth as possible. When the PTFE guide rail needs to be repaired after being worn, the maintenance work is very labor-saving and can be interchanged. It is easy to maintain dimensional accuracy. Especially when the guide rail is damaged and needs to be repaired, it is more advantageous to use plastic for local repair.

2. Friction parts

There are many PTFE friction parts commonly used in mechanical engineering, including bearings, piston rings, and gears. PTFE is an ideal material for piston rings and is widely used in air compressors and water compressors. The PTFE piston ring acts as a compression ring to block liquids or gases. It is commonly used in situations where lubricants or other harsh conditions cannot be used, such as severe corrosion and high safety requirements, can greatly reduce the wear and repeated boring of the cylinder inner wall The number of holes extends the service life of the cylinder. For example, there is a desktop steam hammer, which originally used a metal ring. During the second shift production, under normal circumstances, the inner wall of the cylinder wears up to 7-9ram after half a year, the metal ring is vibrated for 2 to 3 weeks, and sometimes it may break. The piston ring jammed the inner wall of the cylinder and the cylinder had to be replaced. When using PTFE filled for a month, the inner wall of the cylinder wears the only 2mm, and after 10 months, the wear is the only 3mm, and the life is extended by 4 to 5 times or even longer. Almost all piston rings play a sealing role in reciprocating motion and start frequently, so the static friction coefficient is required to be small. Under small loads, the static friction coefficient of PTFE is 25% to 75% lower than the piston rings of other materials. The greater the load, the better its superiority. This has unparalleled superiority in light starting and reciprocating lightness. The result is reduced energy consumption, reduced vibration, and noise, which is conducive to environmental protection. At the same time, PTFE can be used as gears and bearings for motion transmission and power transmission components in a wide range of working conditions and a very harsh environment for light textiles, printing and dyeing, paper making, and food industries.

3. Seals

The use of PTFE film compounded on the surface of the rubber sealing material can improve the solvent resistance and media resistance of the rubber seal, and the price is relatively low. It has been used in the sealing requirements of various harsh occasions. The filled FE sealing material has excellent high and low-temperature resistance and is currently the main substitute for replacing traditional asbestos gasket materials. Carbon fiber-reinforced PTFE seal material has the characteristics of high strength, high modulus, fatigue resistance, creep resistance, high thermal conductivity, low coefficient of thermal expansion, and friction. These comprehensive properties are unmatched by any kind of sealing materials and are ideal advanced sealing materials.

4. Anti-corrosion parts

Modified PTFE has good chemical stability to acid, alkali, salt corrosion media, and can replace metal ceramics for anti-corrosion engineering, especially suitable for high temperature and strong corrosion occasions, such as anti-corrosion equipment, pipes, and fittings in chemical plants. Corrosive friction materials, valves, pumps, heat exchangers, porous plates, and filter materials for highly corrosive media, lining, and coating of chemical equipment.

5. Electrical insulation

Modified PTFE is widely used as an insulating layer for wire rods, tubes, and raw material tapes. It is also used as an insulator for various sockets, supports, high-frequency microwave equipment, and electrodes for the electrochemical industry.

6. Building materials

Glass cloth impregnated with PTFE dispersion is an excellent membrane structure building material. It has an excellent light transmission, which can reduce the cost of lighting and air conditioning. Durability is more than 20 years. It can reduce the cost of painting and cleaning. The construction period for large frame roofs can be shortened. 50%, can reduce the roof material cost by 50% and the total construction cost by 20%. Therefore, it is suitable for roofing materials of outdoor courts, arenas, stadiums, skating rinks, swimming pools, large-scale exhibitions, zoos and botanical gardens, transportation stations, etc.

7. Lubricant additives

Under boundary lubrication conditions, the most effective way to reduce the coefficient of friction is to select suitable lubricant additives, and the PTFE powder machine is a commonly used solid additive. Experiments show that adding a certain amount of solid additives to engine oil can effectively save about 5% of engine fuel oil.

8. Agricultural machinery materials

Utilizing the self-lubricating, hard-adhesive and wear-resistant properties of filled PTFE, it can be widely made into bulldozer plate lining, excavator bucket, and inner liner of dump truck compartment, etc., in order to improve the efficiency and stability of conveying materials.

9. Daily materials

The PTFE-coated ironworking surface is both wear-resistant and has low friction resistance; the PTFE-coated wok and rice cooker have the characteristics of non-stick food; the blade is bonded or inlaid with a PTFE film, and the blade is tight When the cheeks move, the resistance is both small on the skin and soft.

10. Development of new machinery applications

In addition to the application and research results of PTFE machinery industry, considering both material performance and structure, PTFE has broad prospects in the machinery industry of the automotive industry, conventional weapons, ships, aerospace, and atomic energy, medicine, environmental protection, etc.