How to Evaluate the Quality of Rubber Grommets?

The rubber grommet is a commonly used sealing component with simple manufacturing, easy to use, low cost, etc. It is widely used in petrochemical, mechanical and aerospace fields. The following article gives four criteria to judge the quality of rubber grommet. Read on for more information.

● Tear strength

Tear strength reflects the rubber grommet's sensitivity to notching and the ability to resist cracking when subjected to a certain pressure. Tear strength low rubber grommet in the installation and removal of the plate on the state of pressure at the sharp corners are prone to cracking, which is particularly important for non-stick grommets. rubber grommet by aging (aging) treatment, the degree of change in its physical properties on the rubber grommet temperature resistance and service life has a significant impact.

● Physical properties

The physical properties of rubber grommet at high temperatures are an important indicator of the quality of the grommet, which depends mainly on the formulation, mixing and vulcanization process (including pressure, temperature and time of vulcanization, etc.). Usually, the pressure of vulcanization and molding should be at least 9.8MPa, temperature 160~185C, time 3~15min, depending on the type of rubber. In order to improve the production capacity, the rubber grommet should be placed in the oven after vulcanization and molding. The vulcanization process is finally completed by holding the rubber grommet for a certain period of time under uniform temperature. Physical properties will deteriorate with the use of time and temperature increases. Generally, the average life span of a rubber grommet is about two years at the recommended maximum operating temperature for continuous use. Exceeding the maximum temperature by 10°C reduces the average life by about half. However, short-time over temperature has little effect. grommets with good physical properties at room temperature may become poor under high temperature and continuous use. For this reason, it is important to ensure the physical properties of rubber grommets at high temperatures.

● Hardness

Hardness is one of the indicators of the degree of vulcanization of rubber grommets and has an influence on the temperature resistance of the grommet. The higher the hardness, the higher the temperature at which the grommet can be used. Shore (A) hardness is commonly used in China, while IRHD (International Rubber Hardness Unit) is commonly used abroad in the range of 30 degrees to 80 degrees, which is basically the same.

● Compression permanent deformation rate

Compression permanent deformation rate is a measure of the rubber grommet material elastic recovery ability and determining the use of temperature limit is an important basis. The smaller the value, the better the elastic recovery performance and the more beneficial to the sealing performance and average life of rubber grommet at the allowed use temperature. The compression permanent deformation rate will increase with temperature and time and is related to the molecular weight of the rubber, vulcanizing agent, reinforcing agent and other additives, etc. Under the premise that the raw rubber is certain, it mainly depends on the type of vulcanizing agent and the optimal amount of formulation. Using a phenolic compound vulcanizing agent, the compression permanent deformation rate is the smallest; the amine compound vulcanizing agent is the worst.

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