Detailed explanation of the advantages and disadvantages of cast polyurethane elastomer

Casting polyurethane elastomer is called liquid rubber, which is a product produced by pouring a liquid reaction mixture into the mold cavity.



Main Advantages of Cast Polyurethane Elastomers



1. The adjustable range of performance is large.



A number of physical and mechanical performance indicators can be changed within a certain range through the selection of raw materials and the adjustment of formula, so as to meet the different requirements of users for product performance. For example, hardness is often an important indicator for users of products. Polyurethane elastomers can be made into soft printing rubber rollers with Shore A hardness of about 20, and hard steel rolling rubber rollers with Shore D hardness of more than 70. This is difficult to achieve with general elastomer materials. Polyurethane elastomer is a polar polymer material composed of many flexible segments and rigid segments. As the ratio of rigid segments increases and the density of polar groups increases, the original strength and hardness of the elastomer will increase accordingly.



2. Excellent wear resistance



Especially under the working conditions where there are wetting media such as water and oil, its wear resistance is often several times to dozens of times that of ordinary rubber materials. Although metal materials such as steel are very hard, they are not necessarily wear-resistant. For example, in the large-scale water pump in the Yellow River irrigation area, the metal mouth ring and protection ring of the over-current components have been washed by a large amount of sediment, and they will be seriously worn and leaked within a few hundred hours. , while the mouth ring and protective ring (cyclone) covered with polyurethane elastomer continued to run for 1800 hours without being worn. Others such as husker rubber rollers for rice milling, vibrating screen sieves for coal preparation, track race tracks for sports fields, dynamic oil seals for cranes and forklifts, elevator wheels and roller skate wheels, polyurethane solid tires, copiers and Screen printing squeegees, etc. are also the use of polyurethane elastomers. A point to be mentioned here is that in order to improve the friction coefficient of low and medium hardness polyurethane elastomer parts and improve the wear resistance under load, a small amount of aluminum disulfide, graphite or silicone oil can be added to this type of polyurethane elastomer. lubricant.



3. Various processing methods and wide applicability



Castable polyurethane elastomer can be molded by plasticizing, kneading and vulcanization (refer to MPU) like general rubber; it can also be made into liquid rubber, cast molding or spraying, potting, centrifugal molding (referring to CPU ); It can also be made into pellets, which, like ordinary plastics, are formed by injection, extrusion, calendering, blow molding and other processes (referring to TPU). Molded or injection-molded parts can also be machined such as cutting, grinding, and drilling within a certain hardness range. The diversity of processing makes the applicability of polyurethane elastomers extremely wide, and the application fields continue to expand.



4. Oil resistance, ozone resistance, aging resistance, radiation resistance, low temperature resistance, good sound permeability, strong adhesion, biocompatibility and blood compatibility^



These advantages are the reasons why polyurethane elastomers are widely used in military, aerospace, acoustics, biology and other fields.



5. The shortcomings of improving high temperature resistance by adding calcium carbonate and silica, ester urethane elastomer





But cast polyurethane elastomer is not perfect, its main disadvantages are:



1. Large endogenous heat, general high temperature resistance



The normal operating temperature range is -40~120℃. If it needs to be used for a long time under high frequency oscillation conditions or high temperature conditions, corresponding modification measures must be taken in structural design or formula.



2. Not resistant to strong polar solvents and strong acid and alkali media



Under certain temperature, alcohols, acids and ketones will swell and degrade polyurethane elastomers. Solvents such as chloroform, dichloromethane, dimethylformamide and trichloroethylene will swell polyurethane elastomers at room temperature.



3. The recycling of its waste products is an international problem, and it is also a big problem for environmental pollution, because no country in the world can tackle the problem of its waste products treatment.




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