Natural rubber is suitable for mediums such as water, seawater, air, inert gas, alkalis, salt aqueous solution, but not mineral oil and non-polar solvent. The long-term use temperature does not exceed 90 ℃ and the low temperature performance is excellent. It is used above -60℃.
Nitrile rubber is suitable for petroleum products, such as petroleum, lubricants, fuel oil, long-term use temperature is 120 ℃, such as in hot oil resistant to 150 ℃, at low temperature range of -10 ~ -20 ℃.
Neoprene is suitable for seawater, weak acid, weak alkali and salt solution. It has excellent oxygen and ozone aging properties. Its oil resistance is inferior to nitrile rubber and better than other general rubber. Its long-term usage temperature is less than 90 degrees centigrade, the highest usage temperature is no more than 130 degrees, and its low temperature is -30~-50 C.
There are many varieties of fluoro rubber. They have good acid resistance, oxidation resistance, oil resistance and solvent resistance. It can be used in almost all acid media, as well as in some oil and solvents, and the long-term use temperature is below 200.
Rubber sheet as flange gasket, mostly used in pipes or often dismantled manholes, hand holes, the pressure is not more than 1.568MPa. In all kinds of gaskets, the rubber gasket is the softest, and the sealing performance is good and the sealing effect can be brought into play under the smaller pretightening force. Because of this, when the internal pressure is under, it is easily extruded because of the thickness of the gasket or the low hardness.
Rubber sheet is used in benzene, ketone, ether and other organic solvents, prone to swelling, weight gain, softening, sticky phenomenon, leading to seal failure. General swelling of more than 30% can not be used.
Under the condition of low pressure (especially below 0.6MPa) and vacuum, it is more suitable to adopt rubber pads. The rubber material has good compactness and low permeability. For example, fluoro rubber, the most suitable for vacuum container sealing gasket, the maximum vacuum of up to 1.3 x 10-7Pa. When the rubber pad is used in the range of 10-1~10-7Pa vacuum, it is required to be baked and pumped.