sealing materials
Overview of sealing materials


According to the survey by the prospective industry research institute, plastic, rubber, and other seals account for less than 30% of the global sealing product structure, while metal sealing products account for 71% and have a wide range of applications. As an important part of the development of the manufacturing industry, the coordinated development of the sealing industry and upstream and downstream enterprises in the industrial chain is an important factor to measure a country’s national strength and science and technology.

The metal seal manufacturing industry is a downstream industry of steel and non-ferrous metals. The change in steel output and price directly affects the cost and quality of metal seal products and is bound to affect the development of downstream machinery, chemical industry, hydropower, and other industries.

As a powerful industrialized country, China has made great progress in the metal seal manufacturing industry since the reform and opening up, but at present, the metal seal products are still in short supply, and many seal products still need to be imported from abroad, which can not meet the needs of other downstream industries for the standardization and serialization of various seal products.

Especially compared with western developed countries, there are still many places to improve in the manufacturing of seal products in China. Moreover, the number of metal seal manufacturing enterprises in China is small, the output is low, and the overall competitiveness is weak.

In the 1980s, there were more than 1000 seal manufacturers in the inland and coastal areas of Zhejiang, and now there are only more than 1000 seal manufacturers in the whole coastal area. Although the number of patent applications for metal sealing products in China has increased year by year in recent years, the produ ction scale of enterprises has stagnated, the development of science and technology is slow, and some even regress. China’s annual sales of more than RMB 5 million are also in a disadvantageous position in the international competition.

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At present, China is developing rapidly in the field of low-end metal composite sealing products with low scientific and technological content, with fierce competition among enterprises and increasing output year by year. However, the technology of preparing high foaming ratio metal composite sealing materials has been monopolized by the United States and Japan for a long time.

How to break the technical barriers and increase the international competitiveness of China’s sealing field is the primary problem we need to solve. At the same time, with the development of the economy, the gradual improvement of the industrialization process, the crisis caused by resource depletion, and the importance of human beings to the ecological environment, China’s sealing industry is facing more new challenges.

2. Overview of sealing materials

Sealing is a method that can effectively prevent or cut off the mass transfer between media. Its principle is to establish an effective closed system, which adopts some special mechanisms to block the media channel, block the media flow, or increase the fluid flow resistance in the leaking media channel, to achieve the purpose of no leakage. Seals are divided into two categories: the relatively static joint surface is called a static seal, and the relatively moving joint surface is called a dynamic seal.

Static sealing is mostly used in the industrial field. It usually refers to the closed system established when the production system is in the state of installation, maintenance, and stops when the sealing materials and sealing elements in the components are combined with the corresponding sealed product forms without the parameters such as process medium temperature and pressure. A static seal is realized under static conditions, which mainly includes three categories: gasket seal, rubber seal, and contact seal.


Dynamic sealing refers to a sealing way realized by some special means when all sealing structures established by static sealing technology or the sealing structure of crude oil fail or there are problems in instruments and equipment, and the sealed medium is leaking. The dynamic seal can be divided into two types, rotary seal and reciprocating seal. In dynamic sealing, the whole sealing structure is realized under dynamic conditions, and the establishment of its sealing structure is always affected by medium temperature, pressure, vibration, and corrosion.

2.1 Performance requirements of sealing materials

The sealing performance is an important index to evaluate the quality of mechanical products. Because the sealed medium, the working conditions of equipment, and the working environment of sealing products are different, the sealing material should have the ability to adapt to different environments to meet the requirements of sealing function.

The sealing material shall have excellent air tightness, and there shall be no bubble between the sealing material and the sealed parts, to prevent the leakage of the liquid medium due to the damage to the sealing material.

Good compression resilience and flexibility are also important indicators to measure the performance of sealing materials: sufficient elasticity can make the sealing materials have the trend of back compression when being extruded; The softness can make the sealing products easy to be compressed and closely fit with the sealing surface to prevent leakage. The sealing material shall also have certain stiffness, hardness, and mechanical strength.

When subjected to high pressure, the sealing material resisting the pressure difference will be stressed and deformed, greatly shortening the sealing effectiveness. The compatibility between the sealing material and the sealed medium, that is , the tolerance of the sealing material to the sealed liquid, is the main performance parameter of hydraulic sealing products. Excellent hydraulic sealing products shall meet this requirement to ensure that the sealing material does not produce physical changes such as embrittlement and cracking, or chemical changes such as corrosion.

In addition to its excellent performance, sealing materials should also have the characteristics of low price, easy access, convenient storage, and transportation. In addition, its processing performance should also be considered, such as easy pouring, molding, easy machining, easy assembly, etc.


The requirements of sealing materials can be divided into two categories: one is the performance of sealing materials; The second is the sociality at that time, such as material price and source, which is determined by the social demand at that time.

Because of the particularity of its working environment, sealing materials have become one of the most demanding materials. Sealing performance is an important index to evaluate sealing materials.

If leakage occurs during work, it will seriously affect the efficiency of sealed products and even threaten the personal safety of operators. Therefore, the research on the performance of sealing materials is of great significance.

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