What are the physical and chemical characteristics of common filter cloth?
(1) Cotton filter cloth. The heat resistance, wear resistance and tensile strength of cotton filter cloth are good. Because the fiber is short and the swelling degree is good when it is wet, the cotton filter cloth has a good function of intercepting particles. When encountering hot dilute acid and cold concentrated acid, the abrasion resistance and tensile strength of cotton filter cloth decrease; when strong alkali is encountered, the abrasion resistance and tensile strength of the cotton filter cloth will also decrease. The cotton filter cloth is easy to rot and mildew and the application temperature shall not exceed 100 ℃. Cotton filter cloth is not suitable for filtering strong acid and alkali materials, but it is still widely used because of its low price.
(2) Nylon filter cloth. Nylon, also known as nylon, belongs to aliphatic polyamide chemical fiber. Nylon has good wear resistance, tensile strength, elongation and elasticity. The application temperature of nylon filter cloth can reach 100 ℃, and its alkali resistance is also good, second only to carbon tetrafluoride fiber. However, nylon filter cloth is not acid resistant and will be dissolved by chemical reaction in case of concentrated sulfuric acid and hydrochloric acid; It is easy to be oxidized by oxidants. When encountering high temperature or high concentration of oxidants, the oxidation speed is very fast. Nylon filter cloth can be dissolved in organic solvents such as phenol or concentrated formic acid.
(3) Polyester filter cloth. Polyester belongs to polyester chemical fiber, and its scientific name is polyethylene terephthalate. Polyester has good tensile strength, wear resistance and dimensional stability, especially Polyester filter cloth is suitable for rotary drum vacuum filter and belt press filter. Its chemical stability is not very good, but it is resistant to the corrosion of oxidants and reducing agents, and has good acid resistance. However, it is not resistant to concentrated sulfuric acid and phosphoric acid. In case of high temperature and high concentration of alkali, it will have a chemical reaction to dissolve the polyester. In case of phenol solvent, it will be swelling with the progress of concentration and temperature, and will be hydrolyzed in the wet air at high temperature. Therefore, the application temperature is lower than that of other synthetic fibers, about 80 ℃.
(4) Polypropylene filter cloth. Polypropylene fiber is a polyolefin chemical fiber, and its scientific name is polypropylene. Polypropylene fiber has good heat resistance, wear resistance, tensile resistance, acid and alkali corrosion resistance. Polypropylene filter cloth filter cloth is suitable for filtering high-temperature acid and alkali materials. Because it is difficult to dissolve in organic solvents, it is also widely used in the filtration of solvents, paints, dyes, mineral oils, etc. The operating temperature can reach 90 ℃.
(5) Vinylon filter cloth. Vinylon is a kind of polyvinyl alcohol chemical fiber, whose scientific name is polyvinyl formal. Vinylon has good tensile strength, wear resistance and alkali resistance. It is swelling or decomposing in case of concentrated sulfuric acid and hydrochloric acid, insoluble in animal, vegetable oil and mineral oil, and swelling or decomposing in case of hot pyridine and phenol. The operating temperature can reach 100 ℃.
- Cotton, wool and rayon filter cloth. Wool filter cloth has slightly better acid resistance than cotton filter cloth. It can be used to filter thin acidic suspension or high viscosity suspension. It is not alkali resistant and easy to block. Rayon filter cloth has worse tensile function and abrasion resistance than cotton, and worse alkali resistance than cotton filter cloth. However, its other chemical properties are similar to cotton filter cloth, and it can be used for pressing and filtration of suspension containing coarse particles.
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