The modern petrochemical industry has increasingly higher requirements for sealing materials. It requires sealing gaskets to be resistant to corrosion from various media, applicable to a wide temperature range, have sufficient mechanical strength at high temperatures and maintain dimensional stability.
In terms of both corrosion resistance and temperature resistance, polytetrafluoroethylene air filter membrane is undoubtedly the most ideal material. Except for alkali metal complexes, it is almost not corroded by any other media and has a wide range of applicable temperatures. , can withstand -200℃~+200℃ for a long time, and its gas permeability is much smaller than traditional gasket materials such as asbestos and rubber.
However, pure polytetrafluoroethylene PTFE material also has its limitations. The most fatal one is that pure polytetrafluoroethylene gaskets have creep problems. After being used for a period of time, the thickness of the gaskets decreases due to creep, causing the The tightening force of the flange is reduced, causing leakage.
In order for PTFE air filtration membranes to provide effective sealing in various harsh environments, the gasket material must be easily compressible, have good elasticity, be resistant to chemical corrosion, high and low temperature, and have low gas permeability and other characteristics, the method of covering rubber gaskets with polytetrafluoroethylene was first used, and was successfully promoted on some occasions.
However, due to poor rubber properties, it easily swells when exposed to organic solvents and has low mechanical strength. Moreover, the outer polytetrafluoroethylene film is easily broken, causing erosion and leakage. Therefore, people are looking forward to developing a new material. , to provide long-term effective sealing.
Foreign countries began to study the use of filling modification methods to improve the sealing performance of polytetrafluoroethylene PTFE materials as early as the mid-1980s. In 1990, the American GARLOCK company developed a multi-layer composite filled polytetrafluoroethylene with high compression resilience. Fluoroethylene gasket is a three-layer composite of inorganic hollow material and pure polytetrafluoroethylene to obtain a gasket material with excellent mechanical properties and compression resilience.
The currently commercially successful brands mainly include GYLON3504, SIGMA500, etc. This type of gasket is easy to compress and requires only a small bolt tightening force to achieve effective sealing. Therefore, polytetrafluoroethylene air filter membranes can be used For Yutang glass equipment and occasions where the required bolt load is low and sealing requirements are high, PTFE coated gaskets can be replaced.
There are also domestic manufacturers of PTFE air filtration membranes that are imitating them. However, the formula and processing methods of PTFE air filtration membranes are far different from those of foreign countries. The products have poor compression recovery, are prone to leakage, and are easy to break. , short service life, small range of use and other shortcomings.
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