1、 Overview
With the continuous progress of aerospace technology, the sealing requirements of sealing materials are higher and higher. This requires strict control of the performance of sealing materials. Among many sealing materials, carbon sealing materials are the most widely used. Among carbon sealing materials, graphite has excellent characteristics such as high thermal conductivity, high heat resistance, and friction resistance, so graphite is often used as sealing material. However, due to the characteristics of high-speed operation between the shafts of aerospace engines, higher requirements are put forward for the tensile properties of sealing materials. Carbon composites are the key materials used in this device. Carbon composites have excellent properties and Suconvey Silicone Rubber, so carbon composites are used as sealing materials in the field of aerospace.
2、 Carbon sealing materials commonly used in aerospace industry
（1） Flexible graphite sealing material
Flexible graphite sealing material was developed by the United States in the mid-1980s. It is made of high-quality graphite material through deep processing by special technology. Now the types of rice are mainly graphite paper, woven filler, reinforced gasket, and so on. Carbon graphite has good lubricity, low friction coefficient, and high thermal conductivity, which is between white and mild steel. Due to its small expansion coefficient, it can withstand huge temperature differences and has a few dragon shapes. Graphite also has high chemical inertia, so it can not be corroded by most acid-base solutions and organic substances. It is used as sealing material in a few fields of white cotton and white 1, y Aerospace like jiaosiliang lamp.
Although the flexible graphite sealing material retains the excellent performance of ordinary graphite materials and has better compressibility and extensibility than ordinary graphite materials, its strength is too low and can only be used for low-pressure static sealing.
(2) Reinforced graphite composites
Reinforced graphite composites are made by impregnating resin, metal, and other impregnates in porous graphite. The manufacturing processes mainly include pressure impregnation and vacuum impregnation. The strength of reinforced graphite is higher than that of ordinary graphite. It can be used in the friction pair of dynamic seals and the friction part of the rotary joint.
To develop materials that can meet the requirements of modern aerospace technology, scholars at home and abroad have tried to strengthen graphite materials with ceramic particles. The results show that this method is very helpful to improve the strength, friction resistance, and oxidation resistance of composites . However, due to the low lubricity of ceramics and the lubricity of graphite itself, it is not suitable to be used under the condition of high temperature and drying, so the application effect of carbon-ceramic composites in the field of aerospace is not very ideal. Boron nitride has the ability of high-temperature resistance and oxidation resistance and has high lubricity. It can be used under high temperature and dry conditions. The molecular structure of boron nitride and graphite is similar, which makes them have good compatibility. The composite of boron nitride and graphite has both advantages and is suitable for aerospace applications under high-temperature oxidation.
（3） Carbon fiber composites
Three kinds of carbon fiber composites and carbon fiber composites need to be prepared together.
Because of its unique preparation process, excellent lubricity and compressibility, and the unique hardness of flexible graphite, carbon fiber flexible graphite composite has become the best static sealing material so far. Braided carbon fiber resin-impregnated composite is a composite made of asphalt carbon fiber as reinforcement and a small amount of resin as adhesive. Asphalt and resin improve the performance of pure graphite sealing materials, but these products are still in the development stage. Due to the existence of fiber bundles in carbon composites, the sealing performance of carbon composites is greatly reduced.
3、 Preparation process of carbon sealing material
The preform preparation process for the preparation of carbon composite seals mainly includes two processes: carbon fiber preform weaving and perform densification. The preform is mainly composed of carbon felt and three-dimensional fiber braid, and the densification process adopts CVI Process and asphalt impregnation carbonization . The process flow is divided into 8 processes: preform preparation, preform heat treatment, thermal gradient CVI Process, ultra-high pressure impregnation carbonization process, high-temperature graphitization treatment, low-pressure impregnation carbonization resin, machining grinding, and seal products.
4、 Development of carbon sealing materials in China
With the continuous development of the synthetic industry, graphite plays an important role in sealing materials with its unique properties. China’s graphite, represented by other sealing technologies, has promoted the development of sealing technology dominated by high-tech materials and is gradually approaching the international level. However, there is still a certain gap between China’s sealing technology and the advanced technology of developed countries, which is mainly reflected in the backwardness of impregnation technology and weaving equipment. At present, China Silicone rollers Supplier is conducting theoretical research on the properties of carbon composites and then studying the backward technology of production technology, to narrow the gap with the world’s advanced level.
5、 Conclusion
Due to the short research time of carbon sealing materials in China, many preparation processes are not perfect. In addition, carbon composites are difficult in the preparation process, which makes the work of technicians more difficult. However, with the continuous development of China’s aerospace technology and the continuous research on carbon sealing materials, it is believed that the sealing materials with carbon composites as raw materials will be further popularized and developed.
