Natural rubber for water, sea water, air, inert gas, alkali, salt and other media, but not resistant to mineral oil and non-polar solvent, long-term use temperature does not exceed 90 ℃, low temperature performance, Use above.
Nitrile rubber for petroleum products, such as oil, lubricants, fuel oil, long-term use temperature of 120 ℃, such as in hot oil can withstand 150 ℃, low temperature -10 ~ -20 ℃.
Chloroprene rubber for seawater, weak acid, weak base, salt solution, oxygen and ozone aging performance, oil resistance than nitrile rubber and better than other general rubber, long-term use temperature below 90 ℃, the maximum temperature does not exceed 130 ℃, low temperature of -30 ~ -50 ℃.
Fluorine rubber has a variety of varieties, they have a good acid, oxidation resistance and oil resistance, solvent resistance. Can be used in almost any acid medium and some oil and solvent, long-term use temperature below 200 ℃.
Rubber sheet as a flange gasket, used for pipes or often demolition of the hole, hand hole, the pressure does not exceed 1.568MPa. Because in all kinds of gaskets, the rubber gasket the most soft, good fit performance, in the smaller preload can play a sealing effect. For this reason, when subjected to internal pressure, because the pad is thick or low hardness and easy to be squeezed out.
Rubber sheet in benzene, ketone, ether and other organic solvents used, prone to swelling, weight gain, soft, sticky phenomenon, resulting in sealing failure. The general swelling of more than 30% can not be used.
In the low pressure (especially 0.6MPa below), vacuum case, the use of rubber pad is more appropriate. Rubber material has good compactness and low air permeability. Such as fluorine rubber, the most suitable for the vacuum container gasket, vacuum up to 1.3 × 10-7Pa. Rubber pad in the 10-1 ~ 10-7Pa vacuum range, the need for baking and pumping treatment.
The price is lower than other gaskets, easy to use; the biggest problem is: gasket material, although the addition of rubber and some fillers, still can not be filled with those tiny pores completely filled, there is a trace of penetration. Therefore, in highly polluting medium, even if the pressure, the temperature is not high can not be used. When used in some high-temperature oil medium, usually in the late use, due to rubber and filler carbonation, strength, material becomes loose, then the interface and gasket inside the penetration, coking and smoke phenomenon. In addition, Non-Asbestos Rubber Sheet at high temperatures easily bonded to the flange sealing surface, to replace the gasket brought a lot of trouble.
In the heated state, the use pressure of the gasket in various media depends on the strength retention of the gasket material. Asbestos fiber material exists in the crystal water and adsorption water. 110 ℃, the adsorption of water between the fiber has 2/3 precipitation, the tensile strength of fiber reduced by about 10%; 368 ℃, the adsorption of water precipitation, fiber tensile strength reduced by about 20%; more than 500 ℃, Crystal water began to precipitate, the intensity is lower.
The impact of medium on the strength of Non-Asbestos Rubber Sheet is also great. For example, in the aviation lubricants and aviation fuel, 400 oil-resistant Non-Asbestos Rubber Sheet transverse tensile strength difference of 80%, which is due to aviation fuel on the plate of rubber swelling than aviation lubricants serious. Taking into account the above factors, the domestic Non-Asbestos Rubber Sheet XB450 recommended safe use: temperature 250 ℃ ~ 300 ℃, pressure 3 ~ 3.5MPa; 400 oil Non-Asbestos Rubber Sheet temperature should not exceed 350 ℃.
Non-Asbestos Rubber Sheet containing chloride and sulfide, easy to form after the metal flange corrosion of the original battery, especially oil Non-Asbestos Rubber Sheet sulfur content higher than ordinary Non-Asbestos Rubber Sheet several times, so in non-oily media should not be used. Gasket in the oil and solvent-like medium will occur in the swelling phenomenon, but within a certain range, the sealing performance of the basic no effect. For example, No. 400 oil-resistant Non-Asbestos Rubber Sheet in the room temperature aviation fuel for 24 hours soaking test, requiring the increase in oil weight shall not exceed 15%.