The modern petrochemical industry has higher and higher requirements for sealing materials, requiring sealing gaskets to be resistant to corrosion by a variety of media, have a wide application temperature range, have sufficient mechanical strength at high temperatures and maintain dimensional stability. In terms of both corrosion resistance and temperature resistance, PTFE is undoubtedly the most ideal material. Except for alkali metal complexes, it will hardly be corroded by any other medium. It has a wide temperature range and can withstand long-term -200 ℃~+200℃, the gas permeability is much smaller than traditional gasket materials such as asbestos and rubber. However, pure polytetrafluoroethylene PTFE materials also have their limitations. The most fatal thing is that pure polytetrafluoroethylene gaskets have creep problems. After a period of application, the thickness of the gasket decreases due to creep, which makes the flange The tightening force is reduced, causing leakage.
In order to provide effective sealing in various harsh environments, the gasket material must be easily compressed, have good elasticity, chemical corrosion resistance, high and low temperature resistance, and low gas permeability. The first use of PTFE The method of covering rubber gaskets has been successfully promoted in some occasions. However, due to the poor rubber properties, it is easy to swell when exposed to organic solvents, and the mechanical strength is low, and the outer PTFE membrane is easily broken, causing erosion and leakage. Therefore, people look forward to the development of a new type of material to provide Long-term effective sealing.
As early as the mid-1980s, foreign countries began to study the use of filling modification methods to improve the sealing performance of polytetrafluoroethylene PTFE materials. In 1990, the American GARLOCK company developed a multi-layer composite high compression and resilience filled PTFE gasket. The sheet is a three-layer composite of inorganic hollow material and pure PTFE to obtain a gasket material with good mechanical properties and compression resilience. At present, the commercialized grades mainly include GYLON3504, SIGMA500, etc. This type of gasket is easy to be compressed, and it can be effectively sealed with only a small bolt tightening force, so it can be used for pond glass equipment and the required bolt load is relatively low. It can replace PTFE-coated gaskets for low and high sealing requirements. There are also domestic manufacturers who are imitating, but there is a big gap between the formula and processing methods and foreign countries. The products have poor compression recovery, easy leakage, easy breakage, short service life, and small use range.