What is PTFE Gasket

What is PTFE Gasket ?

PTFE gaskets is polytetrafluoroethylene gaskets, which are flat gaskets made of PTFE rods, tubes, and plates by mechanical turning or cutting. , V-shaped gaskets, piston rings, ball valve gaskets, etc. In fluid machinery (such as pumps, compressors, mixing kettles, centrifuges, etc.), the parts with the most severe operating conditions are PTFE gaskets.

The full name of PTFE gaskets is polytetrafluoroethylene gaskets, also called PTFE gaskets, which are flat gaskets made of PTFE rods, tubes, and plates by mechanical turning or cutting. , V-shaped gaskets, piston rings, ball valve gaskets, etc. It has good properties such as corrosion resistance, aging resistance and non-conductivity.  PTFE has a pH value of 0-14 (except for molten alkali metals and fluorine under high temperature and high pressure). It can have good mechanical strength between -100°C and 100°C.

Properties and Applications of PTFE

Polytetrafluoroethylene is a special polymer material with excellent performance. Due to its high price, it was only used in high-precision fields such as military industry, aerospace and nuclear industry for a long time. In recent years, due to economic development and scientific and technological progress, PTFE has begun to enter the civilian field. With its superior performance, it occupies a pivotal position in petrochemical, aerospace, automotive compressors, electronics, semiconductors, medicine, construction, textile industry, food industry, and other industries. Nowadays, domestic PTFE products have made great progress and occupy a large market. In the previous article, we learned about the advantages and disadvantages of PTFE. Today we continue to understand the material characteristics of PTFE in various fields. in the application.

1. Corrosion resistance: The medium in the petroleum, petrochemical and natural gas industry is mostly a variety of liquids and gases with different corrosiveness, so the gaskets used are required to have high chemical corrosion resistance. PTFE gaskets are used in concentrated sulfuric acid and nitric acid , hydrochloric acid, even boiled in aqua regia, its weight and properties have no change, and it is almost insoluble in most solvents, which meets the requirement of corrosion resistance.

2. Sealing: The price of raw materials for chemical products is relatively high, and any leakage will bring great losses to users. Chemical products are more flammable and explosive, and leakage may cause immeasurable serious losses such as fire and casualties. Therefore, there are high requirements for the sealing performance of sealing products, and the density of PTFE gaskets is relatively high, which is 2.14-2.20 grams per cubic centimeter, hardly absorbs water, and the equilibrium water absorption rate is less than 0.01%, which makes it a good seal The material of the product.

3. High and low temperature resistance: Many industries have a strong demand for the high and low temperature resistance of PTFE. Let us take the petrochemical industry as an example, because there are various media gases and liquids such as aromatic hydrocarbons and antirust agents , acid gas, drilling fluid, seawater, carbon dioxide, hydrogen sulfide, etc., and these media are often mixed together and have the characteristics of high temperature and high pressure, while polytetrafluoroethylene is a molecular chain because fluorine atoms replace hydrogen atoms in polyethylene. From a planar structure to a helical structure, the fluorine atoms form a protective shell outside the molecular carbon chain skeleton, so PTFE has good high and low temperature resistance. When used at a temperature of +260 degrees, even when the temperature will be -190 degrees, it can maintain an elongation of 5%. In actual use, it can withstand a high temperature of 280 degrees, and can reach 300 degrees for a short time. When the temperature reaches It begins to sublimate when it is above 290 degrees, but the weight loss rate is small, only 0.0002%.

4. Self-lubricating: The excellent mechanical properties of PTFE are the small friction coefficient, between 0.01 and 0.10, which is the smallest friction coefficient (0.04) among plastics and even all engineering materials. The coefficient of friction is only 1/5 of that of polyethylene, which is also an important feature of the perfluorocarbon surface. The friction coefficient of PTFE increases with the increase of the sliding speed, and tends to be stable when the linear speed reaches 0.5-1.0m/s or more; and the static friction coefficient is smaller than the dynamic friction coefficient, which can be used in bearing manufacturing. Reduce its starting resistance, so that it is very stable from starting to running. The friction coefficient of PTFE decreases with the increase of load, and tends to be constant when the load reaches 0.8 MPa or more. At high speed and high load, the friction coefficient of PTFE is lower than 0.01. From the ultra-low temperature to the melting point of PTFE, the friction coefficient is almost unchanged, and only when the surface temperature is higher than the melting point, the friction coefficient increases sharply. Due to the small intermolecular attraction, PTFE has low hardness and is easily worn by other materials. However, as long as the surface roughness of the abrasive material is appropriate, the wear of PTEF can be reduced to a considerable extent. The PTFE products commonly used in the aerospace field mainly include PTFE and modified PTFE pipes, rods, plates, membranes, guide rings, sealing, sealing balls and other products. In the aerospace field, polytetrafluoroethylene When vinyl fluoride is used as a self-lubricating material, its friction coefficient and wear rate are the focus of design and selection.

5. Electrical insulation: Because the fluorine atoms in the molecular chain of PTFE are symmetrical and evenly distributed, there is no inherent even distance, and the change is small within the range of power frequency 109HZ. Its insulation resistance is very high, even if it is immersed in water for a long time, the change is not significant, and it does not change much with temperature. The breakdown field strength is very high. The breakdown field strength of a very thin PTFE film can reach 200KV/mm , as the thickness increases, the breakdown field strength decreases gradually. In addition, PTFE is the most stable to the arc, and the arc resistance is usually greater than 300s. This is because when the high-voltage surface is discharged, it will not cause a short circuit due to carbonization, and only decompose into gas. Even if it is exposed to the open air for a long time, its insulation will not be affected. PTFE film is suitable for capacitor dielectric, electrical insulation parts used at various frequencies, capacitor dielectric, wire insulation, electrical instrument insulation, etc. PTFE film is suitable for capacitor dielectric, insulation layer of special cables, wire insulation, electrical instrument insulation and sealing gasket.

6. Non-stick: Polytetrafluoroethylene PTFE material has small surface tension and inertness among solid materials, and does not adhere to any substance. The PTFE material is applied to the roller or nested on other parts, used as a guide wheel, PTFE roller, allowing the film, paper, textiles, etc. to pass quickly; it can also be made into thin sheets such as chemical fiber molded sheets, textile lubricating blocks It is installed on the loom to prevent the adhesion of various silk threads and made into special-shaped parts of PTFE for use on mechanical equipment to prevent glue and other adhesions that are difficult to remove; Substrates, etc., these applications are based on the small friction coefficient and non-stick characteristics of PTFE materials, which means that the tension is reduced to the lowest when the product passes through, and the attached dirt is easy to clean.

7. Weather resistance: radiation resistance and low permeability: long-term exposure to the atmosphere can also keep the surface and performance unchanged, which is the best aging life in plastics.