The asbestos board is suitable for any working environment with high requirements, including oil, fuel, chemical industry, refrigerant and steam. It has higher temperature resistance than the asbestos free board. The main material is asbestos fiber. The traditional asbestos material has been used for a long time in China. The reason is that the asbestos fiber board is cheap, high temperature resistant, high strength and good operation performance. The non asbestos board is mainly made of high-strength aramid fiber. The severity of the harm of asbestos material to human health has long been banned in developed countries such as Europe, America and Japan, and China will also Asbestos sealing materials will be gradually eliminated and replaced by non asbestos sealing materials. High temperature resistant rubber, special heat-resistant fiber, glass fiber, reinforcing material and other precision compression combination. According to the requirements of various working conditions, the sealing products of various shapes, which are made of asbestos free base plate materials, punched and sheared by molds or tools, are good substitutes for asbestos oil-resistant rubber plates and green environmental protection sealing materials. At present, asbestos free board has been used in shipping, petrochemical, aviation, automobile and other industries for decades. It is an ideal sealing material for lubricating oil, fuel oil, steam, sea water, compressed air, medium acid and alkali.
The main chain of EPDM is composed of chemically stable saturated hydrocarbons and only contains unsaturated double bonds in the side chain, so it is basically a kind of saturated rubber. Because there is no polar substituent in the molecular structure and the intermolecular cohesion energy is low, the molecular chain can keep flexibility in a wide temperature range. The chemical structure of EPDM makes its vulcanized products have unique properties. 1. Low density and high filling property: EPDM is a kind of rubber with low density and its density is 0.87. In addition, a large amount of oil can be filled and fillers can be added, so the cost of rubber products can be reduced, and the disadvantages of high price of EPDM raw rubber can be made up. For EPDM with high Mooney value, the physical and mechanical properties of EPDM with high filling will not be greatly reduced. 2 aging resistance: EPDM has excellent weather resistance, ozone resistance, heat resistance, acid and alkali resistance, water vapor resistance, color stability, electrical performance, oil filling and room temperature fluidity. EPDM rubber products can be used for a long time at 120 ℃, 150-200. C can be used temporarily or intermittently. The use temperature can be increased by adding suitable antioxidant. EPDM crosslinked with peroxide can be used under more severe conditions. When the concentration of ozone is 50 × 10 ~, the tensile strength of EPDM is 30%, it can reach 150 hours without cracking. 3 corrosion resistance: due to the lack of polarity and low unsaturation of EPDM, it has good resistance to various polar chemicals such as alcohol, acid, alkali, oxidant, refrigerant, detergent, animal and vegetable oil, etc.; however, it has poor stability in aliphatic and aromatic solvents (such as gasoline, benzene and mineral oil). Under the long-term action of concentrated acid, the performance will also decline. In ISO / tr7620, nearly 400 kinds of corrosive gaseous and liquid chemicals were collected. There are more than 80 kinds of chemicals with the action degree of 1 grade EPDM, which are listed here. Water vapor resistance: EPDM has excellent water vapor resistance and is superior to its heat resistance. In 230 ℃ superheated steam, the appearance did not change after nearly 100 h. But under the same conditions, the appearance of fluororubber, silicone rubber, fluorosilicone rubber, butyl rubber, rubber and natural rubber deteriorated obviously in a short time. 5. Hot water resistance: EPDM is also good in hot water resistance, but it is closely related to the curing system used. TMTD is the EPDM of the curing system. After soaking in 125 ℃ superheated water for 15 months, the mechanical properties change little, and the volume expansion rate is only 0.3%. Electrical properties: EPDM has excellent electrical insulation and corona resistance, and its electrical properties are better than or close to that of SBR, CSPE, PE and XLPE. Elasticity: there is no polar substituent in the molecular structure of EPDM, and the molecular cohesion energy is low. The molecular chain can keep flexibility in a wide range, second only to natural rubber and cis-1,4-polybutadiene rubber, and can still keep at low temperature. Adhesion: due to the lack of active groups in the molecular structure of EPDM, the cohesive energy is low, and the compound is easy to spray frost, so the self adhesion and mutual adhesion are poor
Asbestos gasket is a product made of asbestos, so what requirements does the product need to meet to meet the requirements of qualified products? First of all, it needs to meet the use of various environments, and the important thing is the overall use performance of the product. If there is a problem with the performance of the product, its use effect will be greatly affected. Therefore, if you want to make the product work well, you must meet the requirements of good performance. Secondly, it should also meet the needs of high quality and high reliability, otherwise it will greatly affect the final use effect of Zui. Therefore, the use of the product by people should ensure the high reliability of the product. It also needs to have corresponding use functions, which should meet the overall functional requirements for any product. The main function of the product is to provide better help for people
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