Development status and trend of rubber and plastic sealing technology

2. Rubber and plastic sealing material

Compared with developed countries in Europe and the United States, China's polymer material synthesis industry is still in the rapid catch-up stage, the lack of rubber and plastic sealing special varieties, and the lack of stability of domestic materials, which affects the performance of rubber and plastic sealing. The main raw materials of domestic high-end rubber and plastic seals are currently basically dependent on imports, and the research and development work of related materials is also mainly focused on the coordination and modification of imported materials.

With the relentless pursuit of higher quality of life, science and technology have been developing rapidly. As for mechanical engineering technology, it is developing in the direction of green and intelligent. In order to meet the requirements of green manufacturing, energy saving and environmental protection, and long life, high reliability and micro/zero leakage of mechanical equipment under extreme environment/harsh working conditions, the performance requirements of polymer sealing materials are also getting higher and higher, which will face more difficult challenges for China's polymer materials industry, which is already in a backward stage. However, in any case, understanding the development trend and requirements of relevant materials is conducive to promoting the development of relevant industries in our country, mainly including the following aspects:

(1) High and low temperature range

On the lunar surface, the night is as low as -160 ~ -180 ° C, the day is as high as 130 ~ 160 ° C, and the temperature difference is as high as 340 ° C, which puts forward high requirements for the high and low temperature resistance of the polymer sealing material and the adaptation to the ultra-wide temperature range.

(2) High speed and high pressure

The hydraulic system has developed to 80000 r/min, 105 MPa grade, and the deep well pressure can reach 140 MPa, which requires the polymer sealing material to have excellent pressure resistance, extrusion resistance, low friction and wear performance and compressive permanent deformation resistance.

(3) Complex medium environment

The wide application of new fuel oil, new lubricating oil and various additives that have a strong corrosive effect on polymer materials in automotive engines and hydraulic systems, as well as complex medium environments such as deep well drilling, metallurgy, chemical and petroleum multi-medium hydraulic and pneumatic components, all put forward higher requirements for the dielectric resistance characteristics of polymer sealing materials. CHANG et al. used different fillers to fill and modify nitrile butadiene rubber to obtain a series of sealing composite materials with better coolant resistance. Xu Yuduo et al. modified nitrile butadiene rubber by blending to improve the ozone resistance and gasoline resistance of seals. Taking the oil seal as an example, the actual working medium environment is complex, in addition to the modification of the matrix material, in order to improve the sealing and maintaining ability of the oil seal, on the basis of the all-rubber material oil seal, and the development of metal skeleton oil seal, cloth oil seal and other rubber seals, while installing the spring can improve the sealing force, when the friction pair end face wear compensation effect, reduce the leakage rate.

(4) High vacuum

The vacuum degree of space equipment has reached 1.33×10-7 Pa, and the deep space can even reach 10-10 Pa order of magnitude. High vacuum requires that polymer sealing materials not only have good compression resistance to permanent deformation, but also have excellent air permeability resistance, gas expansion resistance and small vacuum loss characteristics, so as to avoid sudden blasting failure under special or sudden circumstances.

(5) High cleanliness

In the fields of nuclear energy applications, semiconductor processing and chemical and pharmaceutical industries, the degradation and aging of polymer sealing materials, volatilization or extraction of additives, etc., may cause incalculable losses, which has strict requirements for the selection of matrix materials, vulcanization and coordination systems.

(6) Constant low friction and wear characteristics

With the rapid development of hydraulic transmission and control technology, the requirements for control and positioning accuracy are getting higher and higher, so the sealing system is required to have a low and constant friction factor, which requires smooth operation at low pressure and low speed, and a long service life at very short stroke and high frequency. QI, WANG, Mi Xiang et al. studied the effect of polytetrafluoroethylene (PTFE) material combined with anti-friction agent on the friction and wear properties of seals. Common antifriction agents are PTFE, polyimide and other polymer powder, and molybdenum disulfide, graphite and other inorganic fillers. In addition to the addition of anti-friction agents, surface treatment processes such as surface irradiation, fluoridation, spraying, etc., can reduce the friction factor of the material and maintain good wear resistance.