In mechanical systems, seals play a huge part in keeping the movement and operation secure. These seals come in different shapes and structures, such as O-rings, U-rings, diaphragms, lip seals, and many more, also of different materials, which are specified for different uses.
Natural Rubber (NR), also known as Isoprene or latex (working temperature: 0 ~ 80℃) is applicable to water and oil-free air, but not to petroleum products.
Silicone Rubber (working temperature: 7 ~ 260℃) is applicable to water, oil-free air, and high-temperature steam, but not to petroleum products.
Ethylene-propylene Rubber (EPR) (working temperature: -50 ~ 150℃) is applicable to water, oil-free air, dilute acid, and other chemicals, but not to petroleum products. It’s usually used for seals dealing with refrigerants.
Nitrile Butadiene Rubber (NBR) (working temperature: -40 ~ 120℃) is applicable to petroleum products, air, animal or vegetable oil, and mineral oils, but not to hot water or hot dry air of more than 60℃.
Fluorocarbon (FKM) Rubber or commonly known under the name of VITON (working temperature: -20 ~ 250℃) is applicable to a variety of strong acids, petroleum, halo-hydrocarbon, grease, hydraulic fluid, vegetable, animal, and mineral oil-based products also air containing hydrocarbons.
Teflon (working temperature: -55 ~ 260℃) is applicable to oils, water, and steam. In addition to that, it also has high mechanical strength and a very low friction coefficient -- which gives it a lubricating property. For this reason, Teflon is a suitable material for wear rings, guide rings, and check rings.
Nylon (working temperature: -40～120℃) is applicable to water, oil, and most chemicals. It also has a very low friction coefficient, enabling its usage without any additional lubricants. Similar to Teflon, Nylon is also used for guide rings, support rings, verge rings, and check rings.
Comparing the different materials shown in the list above, rubber is one of the most common sealing materials. Depending on the materials used, different types of seals can be utilized for different applications. One of the most common types of seals used is the O rings.
Rubber seals have been widely applied in many fields, such as in the chemical industry, military and defense industry, mining, transportation, petroleum, metallurgy and machinery manufacturing, and also other manufacturing industries. This being said, different types of rubbers should be present for different uses.
Common rubber compounds and mixtures for seals:
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Silicone Rubber Seals: Silicone rubber has fantastic resistance under ozone exposure and weathering conditions, with also the ability to maintain its unique flexibility under the working temperature of -55～250℃. It is suitable for manufacturing gaskets for thermal processes, also including seals for intense light sources and valve gaskets. A problem for its application lies in its tensile strength -- it’s not as good as general rubbers. Silicone rubber also has a poor capability of withstanding most concentrated solvents, oils, concentrated acids, and alkalis. Silicone seals are generally used in household appliances, such as electric water heaters, electric irons, and microwave ovens. The silicon rubber material itself can also be used for various products in contact with the human body as an insulation layer, such as kettles and water dispensers.
Posted by Mars Ma
Mars Ma is a Mechatronics Engineer with a knack for IoT products. He believes the cool things you do with your software and electronics wouldn't be possible without resilient cases and other mechanical parts, and that's thanks to his structural engineering expertise.