Most of the O-rings are made of nitrile rubber of various grades and hardness (such as 40 to 90 degrees). Among them, a typical general-purpose material is low/medium nitrile rubber with a hardness of about 75 degrees. Nitrile rubber has good heat resistance, and it can work in the range of 100~120℃. Nitrile rubber has good resistance to mineral oil and lipids, and has a wide range of working fluids (including water and glycol).
Different rubber formulations have different applicability to media: Generally speaking, nitrile rubber is resistant to oil; neoprene rubber has good weather resistance and ozone resistance; acrylic rubber and fluorine rubber are heat resistant; polyurethane rubber is resistant to high pressure and abrasion; copolychlorohydrin rubber is resistant to low temperature and oil. Different rubber formulations and components have different applicability to media.
Material selection analysis of engineering machinery seals:
O-shaped sealing ring for general machinery, the hardness is between 70 and 90 degrees. As an O-type sealing country for static sealing, the material hardness is usually 70 Shore hardness, which is harder than dynamic seals. O-rings for rotating motion generally use butyl rubber material for good effect, and the hardness should be HS=80. In the occasions with low internal pressure and low friction, the hardness is allowed to be lower than 70 degrees; while under high pressure or in rotating motion, it can be higher than 80 degrees, but it is rarely used.
Material selection analysis of hydro-pneumatic sealing ring:
The material selection of O-rings for hydraulic and pneumatic equipment considers the relationship with temperature. The medium is petroleum-based hydraulic oil O-rings. When the temperature is -50~120℃, nitrile rubber is used, and within the range of 120~230℃ Use silicone rubber (mainly static seal), fluorine rubber for dynamic seal within 200℃. When the sealed medium is fuel oil, it is better to use higher than nitrile rubber. In high aniline point oils such as turbine oils, because nitrile rubber will shrink, it should be used with caution. Nitrile rubber will swell in ethanol hydraulic oil, so it cannot be used, and styrene butadiene rubber should be used instead. In recent years, in order to prevent fires, non-flammable phosphate ester hydraulic fluids have been used. In this case, fluoroelastomers are suitable.