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Characteristics and application progress of polyurethane elastomer
Date of accession: July 2006-19 Source:-
With the development of society and the progress of technology, the application of new materials is more and more extensive. Since the early 1980s, polyurethane elastomer has changed from military to military and civilian use, with the increasing variety and brand of products and the expanding production scale, playing an increasingly important role in various sectors of the national economy and people's daily necessities. In this paper, the advantages and disadvantages of polyurethane elastomer, the present situation and prospect of its application and development are discussed from the perspective of practical application.
I. Main advantages of polyurethane elastomer
1, with wide adjustable range of performance. Through the selection of raw materials and the adjustment of formula, many physical and mechanical performance indexes can be changed in a certain range to meet the different requirements of users for product performance. For example, hardness is often an important indicator of users. Polyurethane elastomer can be made into soft printing cots with Shore A hardness of about 20 or hard steel roller cots with Shore D hardness above 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 the elastomer will also increase accordingly.
2. 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, which are over-flow components, are seriously worn and leaked within several hundred hours after being washed by a large amount of sediment, while the mouth ring and protection ring coated with polyurethane elastomer are still not worn after continuous operation 1800 times. Other materials, such as rubber roller of husker, sieve plate of coal preparation vibrating screen, track track of sports ground, power oil seal ring of lifting forklift, elevator wheel, roller skates, etc., are also useful places of polyurethane elastomer. It should be mentioned here that a small amount of lubricant such as aluminum disulfide, graphite or silicone oil can be added to this kind of polyurethane elastomer to improve the friction coefficient of polyurethane elastomer with medium and low hardness and improve the wear resistance under load.
3. Various processing methods and wide applicability. Polyurethane elastomer can be molded by plastication, mixing and vulcanization (MPU) like ordinary rubber. Can also be made into liquid rubber, casting or spraying, packaging, centrifugal molding (refers to CPU); It can also be made into granular materials, and shaped by injection molding, extrusion, calendering, blow molding and other processes (referring to CPU) like ordinary plastics. Molded or injection molded parts can also be machined within a certain hardness range, such as cutting, grinding and drilling. Due to the diversity of processing, the applicability of polyurethane elastomer is very wide, and the application field is expanding.
4, oil resistance, ozone resistance, aging resistance, radiation resistance, low temperature resistance, good sound transmission, strong adhesion, excellent biocompatibility and blood compatibility. These advantages are the reasons why polyurethane elastomers are widely used in military industry, aerospace, acoustics, biology and other fields.
Second, the disadvantages of ester polyurethane elastomer
However, polyurethane elastomer is not perfect, and its main disadvantages are:
1, high endogenous heat and average high temperature resistance. The normal operating temperature range is -40~ 120℃. If it is necessary to work at high frequency oscillation or high temperature for a long time, corresponding modification measures must be taken in structural design or formula.
2, not resistant to strong polar solvents and strong acid and alkali media. At a certain temperature, alcohol, acid and ketone will swell and degrade polyurethane elastomer, while chloroform, dichloromethane, dimethylformamide and trichloroethylene will swell polyurethane elastomer at room temperature.
Third, the application and development of polyurethane elastomer
To sum up, the comprehensive properties of polyurethane elastomer are excellent. In recent years, all countries are strengthening application development research according to market demand, and the development focuses on the following aspects:
1, polyurethane elastomer for automobile. Today's automobile industry is developing in the direction of high performance, low weight, comfort and safety. Rubber-plastic synthetic materials are gradually replacing metal materials, which opens up a very broad prospect for the application of polyurethane elastomers. Goodrich Company of the United States has developed the second generation TPU, and its commercial name is Estaloc. This product keeps the characteristics of the first generation TPU Estaloc, uses hollow glass balls as fillers, and improves the gloss by more than 15%, which can be used to manufacture automobile side panels and shock absorption pads. Installing airbags on cars is the need of the development of modern automobile industry and plays an important role in protecting the life safety of drivers. This kind of airbag must have a certain strength to withstand high-speed impact and good low-temperature flexibility, so it is suitable to be made of polyurethane, and the amount of glue used for each airbag is about 300 grams. Most domestic cars are not equipped with airbags, so there is a great market demand. Using the high strength and bearing capacity of polyurethane elastomer. It can be used to manufacture middle and low speed truck tires with high strength and bearing capacity, and its bearing capacity is 7 times that of the same specification tires made of natural rubber. In recent years, a new type of green polyurethane composite tire is being developed. On the basis of old and new rubber flat tires, it is poured with a certain thickness of polyurethane rubber surface with high wear resistance and puncture resistance. At present, it is in the mileage test stage and is expected to be put into production soon.
2. Polyurethane elastomer for building. The traditional linoleum waterproof material is gradually replaced by durable integral polyurethane waterproof material; 10 years ago, only the national official competition venues used polyurethane paving materials, but now most provincial and municipal stadiums, universities and even some primary and secondary schools have laid polyurethane plastic runways; The expansion joints of large bridges, airport runways and expressways have also begun to use polyurethane elastomer cured at room temperature to make sleepers for high-speed railways, which is an ideal material. Sleepers laid on tunnels and bridges passing through Shinkansen railway in Japan are made of polyurethane elastomer. This new application gives full play to the characteristics of light elasticity, good shock absorption and aging resistance of polychloric acid, and has good popularization value.
3. Chlorinated elastomer for mining. Coal mines, metal mines and non-metal mines have great demand for non-metal materials with high wear resistance, high strength and high elasticity. In recent 10 years, many selected coal plants have replaced heavy metal sieve plates with PVC elastic sieve plates, which not only greatly prolongs the service life of sieve plates, but also significantly reduces the noise in the operating environment, and has obvious energy-saving and consumption-reducing effects. Others, such as cyclone for solid separation, flame-retardant antistatic wear-resistant conveyor belt, solid core wheel of mine monorail crane, combined plate for coal mine shotcrete machine, oil seal ring on 10,000-ton electric wheel dump truck, and cold patching glue for high-voltage cable sheath, have also played a great role in mine construction. At present, there are many wear-resistant elastic products for mining waiting for us to develop and popularize.
4. Polyurethane elastomer for shoes. Since Taiwanese businessmen came to the mainland one after another, the footwear industry in China has developed rapidly. Polyurethane elasticity has the advantages of good cushioning performance, light weight, wear resistance and anti-slip, and has become an important supporting material in the shoe-making industry. Many shoes have important accessories such as soles, heels, toe caps and insoles, such as golf shoes, baseball shoes, football shoes, ski shoes and safety shoes. All of them are made of polyurethane elastomer, which is not only beautiful and elegant, but also comfortable and durable, and can also improve sports performance.
5. Medical polyurethane elastomer. Good biocompatibility, blood compatibility and no additives are the important reasons why TPU and CPU materials are used in medical field. At present, the medical elastomer products that have been successfully developed are: tracheal cannula, prosthesis, suppository for family planning, skull defect repair materials, condoms and so on. Their application prospects in medical and health fields are still very broad.
6. New polyurethane composite board. Britain is developing a polyurethane composite board called SPS plywood system, which will bring a revolution to shipbuilding. It consists of two layers of 9mm thick steel plates and 40mm thick polyurethane elastomer injected between them. Once successfully developed, it can replace the traditional reinforced steel plate materials used in shipbuilding industry. Its advantages are: saving manufacturing time, saving steel plates, reducing hull weight, impact resistance, fatigue resistance, shock absorption, noise reduction and heat insulation. Once the composite materials of SPS system are used in shipbuilding in the future, the consumption of polyurethane elastomer in shipbuilding industry will be a very amazing number.
Note: This information has not been confirmed by China Plastics Industry Network and is for reference only.