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Deficiencies of PTFE and improvement methods

Views: 0     Author: Site Editor     Publish Time: 2023-02-16      Origin: Site

PTFE has many excellent properties, strong acid and alkali resistance oxidant, resistance to various solvents, high temperature resistance 260 degrees, low temperature up to -192 degrees, not aging, lubrication coefficient is very small, high insulation, etc., although the nature of the usual use and relatively stable, but its shortcomings are also very obvious. In the development and use of a variety of PTFE excellent performance at the same time, many of its defects but limit the use of PTFE, see PTFE has so many defects you dare to use? In order to better use PTFE this important material, the following we talk about its shortcomings and improvement methods from ten aspects:.

First of all, PTFE products hardness is low, generally pure PTFE products hardness of Shore 55 or so, which makes PTFE products in terms of pressure resistance deformation, can not withstand excessive pressure, such as made of gasket gasket, if screwed very tight, it is easy to make it plastic deformation or cold flow, which is poor creep resistance, so the need to modify the treatment, adding certain fillers to enhance performance.

Second, its wear resistance is not ideal, the use of tetrafluoro products friction coefficient is very small characteristics of the application is more widespread, but at the same time the products in and the movement of the couple, wear resistance is not enough, poor mechanical strength, rigidity is not enough, such as made of oil-free lubrication bearing, if the speed is fast, then we must often replace the bearing, affecting the normal use, which also needs to be improved by adding wear-resistant materials to solve;.

Third, PTFE material surface energy is poor, so that it has non-stick characteristics with other substances, although in the textile, glue, fluid and other methods have a great help, but also limit its application in industry, then we have to give it surface sodium treatment, etc., so that it can be bonded with other materials;.

Fourthly, PTFE resin is mainly molded products, resin powder has poor fluidity, and many parts are often made into semi-finished products by molding and extrusion, and then finished products by finishing. PTFE melt viscosity is high, even if the heating temperature increases to the decomposition temperature of the melting point temperature, still can not flow, and other thermoplastics molding methods can not be processed. Almost every molded part requires a set of molds, which makes the processing cost rise, and the total cost is expensive because of the high price of PTFE raw materials. The complexity of processing tetrafluoro and the limited scope of application.

Fifth, the coefficient of thermal expansion of tetrafluoro is on the high side, and its linear expansion coefficient changes very irregularly with the change of temperature, and the cold and heat shrinkage changes greatly, which leads to its processing dimensional stability is not ideal. Sintering and cooling or machine tool processing of the object, with the change in ambient temperature will still be significantly changed, which is not entirely due to internal stress but the factor of excessive coefficient of linear expansion. Another example in the application of anti-corrosion equipment, as a container lining it is not the same as the coefficient of linear expansion of the metal shell, in the fluid hot and cold changes and negative pressure operating conditions, due to technical molding defects, it and the container adhesion together, so PTFE lining is prone to deformation, delamination, internal deflation and other phenomena, so for the time being, pure PTFE processing of precision parts is not applicable;.

Sixth, PTFE is usually safe and non-toxic products, but in the ultra-high temperature state, such as in 380 above high temperature heating will be released with highly toxic ions released, which requires attention to open fire, welding or high temperature heating when ventilation safety and prevention.

Seventh, although its electrical properties are very good, with the smallest dielectric constant in solid materials, dissipation factor, high frequency, volume and surface resistance shows the maximum value that has the best insulating properties, but PTFE depends on the sintered products, itself with a very high static electricity, many occasions are not allowed to use, then we need to add anti-static materials for this situation, become anti-static products.

Eighth, Teflon parts are molded, high pressure tightness, high density, sintered size shrinkage is small. If the pressure is light, the size of the cooling shrinkage is large, and is a kind of irregular shrinkage. PTFE parts require a wide range of tolerances, can not be the same as iron, can be precision machined. Its thermal expansion change is 10 times greater than that of iron. Many people mark tolerances are made as required for steel parts, so much so that after actual machining, cooling shrinkage or changes by heat and cold may go out of the tolerance range. Directly molded and sintered processed PTFE plate, tolerance is also relatively large, such as processing PTFE plate: specifications for the thickness of 10mm, thickness tolerance according to industry standards for (+ 1.00, - 0.50).

Ninth, Teflon products are inert, so they do not stick to any object. But we often encounter the problem of bonding or welding in use, where the bonding method are: discharge treatment method and alkali metal solution treatment method can make tetrafluoroethylene parts and other materials for bonding. The discharge method is to put the Teflon parts in the plasma generator or glow discharge tube by evacuating, pass into the trace inert gas to activate it, and then react with the surface of the Teflon parts. Alkali metal solution treatment method has many kinds of processes, the most commonly used is naphthalene - sodium complex solution chemical treatment method. But no matter how to bond, the binder used has temperature resistance, bond strength, etc. to generate the solidity between the tetrafluoroethylene parts still needs to be improved; and the use of heat welding treatment can also solve part of the four parts connected to each other, but the welding rod material and tetrafluoroethylene parts material is generally slightly different, their welding solidity is not enough, also needs to be improved.

Tenth, polytetrafluoroethylene thermal conductivity is low, thermal conductivity is poor, slow heat dissipation, as if a thick plate surface feel warm by hand a little, the plate is higher inside, and temperature changes, the material will also shrink. Because of the slow heat dissipation, affect it as bearings and other thick-walled products require the use of heat-conductive materials, of course, adding filler materials or a certain effect.

In short, polytetrafluoroethylene has outstanding performance, resistance to moisture does not stain water and oil, high temperature stability, low temperature is not embrittlement, aging resistance is not flammable, can be applied to the stronger corrosive pipelines, containers, pumps and valves and radar, high-frequency communication equipment and other special requirements of the occasion, but also for high insulation of electrical, electronic, military aerospace field, but its comprehensive performance still has many deficiencies, need to be improved in many working environments It can be widely used. Our company is continuously using tetrafluoro products to develop the application of tetrafluoro products with high performance, and also exploring its shortcomings, and how to improve its defects to better expand the application space of PTFE for our customers.





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