Advantages and disadvantages of cast polyurethane elastomer

Pouring polyurethane elastomer, called liquid rubber, is a product produced by pouring liquid reaction mixture into the mold cavity, which is the most widely used and the largest output among polyurethane elastomers.

Main advantages of cast polyurethane elastomer

The adjustable range of performance is large

Many physical and mechanical performance indexes can be changed in a certain range through the selection of raw materials and the adjustment of formula, so as to meet the different requirements of users for the performance of products. For example, hardness is often an important index for users. Polyurethane elastomer can be made into both soft printing cots with Shore A hardness of about 20 and hard steel rolling cots with Shore D hardness of over 70, which is difficult for ordinary elastomer materials to do. Polyurethane elastomer is a polar polymer material composed of many flexible segments and rigid segments. With the increase of the proportion of rigid segments and the density of polar groups, the original strength and hardness of elastomer will increase accordingly.

Excellent wear resistance

Especially in the presence of water, oil and other wetting media, its wear resistance is often several times to dozens of times that of ordinary rubber materials. Although metal materials such as steel are hard, they are not necessarily wear-resistant. For example, in a large water pump in the Yellow River irrigation area, the metal mouth ring and protection ring of its flow-through parts are seriously worn and leaked in less than a few hundred hours after being washed by a lot of sediment, while the mouth ring and protection ring (cyclone) coated with polyurethane elastomer are still not worn after continuous operation for 1800h h. Other applications of polyurethane elastomer include rubber roller of rice husker, sieve plate of vibrating screen for coal preparation, track track of sports ground, dynamic oil sealing ring for crane forklift, elevator wheel and roller skates, solid polyurethane tire, copier and screen printing scraper. It should be mentioned here that a small amount of lubricants such as aluminum disulfide, graphite or silicone oil can be added to this kind of polyurethane elastomer to improve the friction coefficient of medium and low hardness polyurethane elastomer and improve the wear resistance under load.

Various processing methods and wide applicability.

Pouring polyurethane elastomer can be molded by plastication, mixing and vulcanization (MPU) just like general rubber. It can also be made into liquid rubber, cast and molded or sprayed, encapsulated and centrifugally molded (referring to CPU); It can also be made into granules, which are shaped by injection, extrusion, calendering, blow molding and other processes (referring to TPU) just like ordinary plastics. Molded or injection molded parts can also be machined such as cutting, grinding and drilling within a certain hardness range. Due to the diversity of processing, the applicability of polyurethane elastomer is very wide, and the application field is expanding.

Excellent physical and chemical properties

The advantages of oil resistance, ozone resistance, aging resistance, radiation resistance, low temperature resistance, good sound transmission, strong adhesion and excellent biocompatibility and blood compatibility are the reasons why polyurethane elastomers are widely used in military, aerospace, acoustics, biology and other fields.

Improving the high temperature resistance and adding calcium carbonate and silica are the shortcomings of ester urethane elastomer, but the casting polyurethane elastomer is not perfect, and its main disadvantages are:

1) High endogenous heat and high temperature resistance. Generally, the normal use temperature range is -40-120℃. If it needs to work under high frequency oscillation or high temperature for a long time, corresponding modification measures must be taken in structural design or formula.

2) Alcohol, acid and ketone will swell and degrade polyurethane elastomer at a certain temperature, and solvents such as chloroform, dichloromethane, dimethylformamide and trichloroethylene will swell polyurethane elastomer at room temperature.

3) Its waste recycling is an international problem, and its environmental pollution is also a big problem, because no country in the world can tackle the problem of its waste disposal.

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