Development status of the hottest high temperature

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Development status of high temperature resistant polyimide

polyimide (PI) is a high temperature resistant polymer, which can maintain its main physical properties at 550 ℃ for a short time and can be used near 330 ℃ for a long time. Among high temperature resistant engineering plastics, it is one of the most valuable varieties. It has excellent size and oxidation stability, chemical resistance and radiation resistance, as well as good toughness and softness. It can be widely used in aviation/aerospace, electrical/electronics, locomotives, automobiles, precision machinery, automatic office machinery and other fields

due to the very stable aromatic heterocyclic structure in the polyimide molecule, it reflects the excellent performance that other polymer materials cannot compare: mild and low temperature resistance. PI synthesized from biphenyldianhydride and p-phenylenediamine has a thermal decomposition temperature of 600 ℃. It is one of the polymers with high thermal stability so far. At such a temperature, the original physical properties can be basically maintained in a short time. It can be used under 333 ℃ for a long time, and it will not crack at -269 ℃; The mechanical strength is high, and the tensile strength of homobenzene type PI film can reach 170Mpa, while that of biphenyl type can reach 400MPa, which changes little with the increase of temperature; Good radiation resistance; Excellent dielectric properties; Stable chemical properties, very stable to acids and bases; In addition, PI has strong creep resistance and excellent friction performance

in 2003, the global consumption of polyimide was about 35000 tons, with more than 50 major manufacturers. At present, the consumption of the United States, Western Europe and Japan has exceeded 20000 tons/year, including 13000 tons/year in the United States. It is expected that the consumption of the United States, Western Europe and Japan will reach 27000 tons/year in 2004. There are 14 factories in the United States, 11 factories in Western Europe and 13 factories in Japan that produce PI. In addition, Russia, China, India, South Korea, Malaysia and Taiwan all produce and consume PI in small quantities. Polyetherimide (ulterm) accounts for about 70% of the PI demand in the United States. Due to its good performance and processing characteristics, it tends to compete with polyethersulfone, polyphenylene sulfide and other aromatic pi. It is expected that the global demand for polyimide will increase at an average annual rate of about 10% in the next few years

China has almost started the research and development of polyimide at the same time as the world, and has basically formed a development and research pattern. Several major PI varieties have been developed, such as benzene type, partial anhydride type, biphenyl dianhydride type, bisphenol A dianhydride type, monoether dianhydride type, ketone dianhydride type, etc., and have been preliminarily applied. At present, there are nearly 20 manufacturers, and the production capacity has exceeded 800 tons/year. In 2002, the PI film market became stronger, with a production capacity of 750 tons/year. In 2003, six manufacturers increased their production capacity by 400 tons/year, and the number of manufacturers expanded to 26. Four manufacturers have exported films, and with the export of copper foil, the national export volume is nearly 70 tons/year. At present, the main manufacturers include Shanghai synthetic resin Research Institute, Changshu Aerospace insulation material factory, Baoying Yabao insulation material factory, Northwest Chemical Industry Research Institute, Sichuan University Experimental Factory, etc. In 2001, the domestic output was about 400 tons. China has also developed rapidly in PI molding materials in recent years. Shanghai synthetic resin research institute has developed a variety of products, Northwest Research Institute of chemical industry produces bismaleimide, and Jilin Changchun Yinghua Institute and Jilin high tech company produce biphenyl PI molding materials

compared with foreign products in many varieties, China has a great competitive advantage in price. Therefore, China's electrical insulation film market is basically occupied by domestic products, and China has begun to export products to foreign countries. For example, Northwest Research Institute of chemical industry exports 30 tons of bismalamide to Europe every year, and Shanghai synthetic resin research institute also exports a small amount of products every year

at present, thermoplastic polyimide is mainly used in automotive engine parts, oil pump and air pump covers, high-temperature sockets for electronic/electrical instruments, connectors, printed circuit boards and computer hard disks, integrated circuit chip carriers, aircraft internal cargo systems, etc

there are many varieties of polyimide, but at present, the main varieties are polyether imide (PEI), polyamide imide (PAI) and bismaleimide (BMI). The current development trend of Pei is to introduce p-phenylenediamine structure or alloy with other engineering plastics to improve its heat resistance, or alloy with polycarbonate, polyamide and other engineering plastics to improve its mechanical strength; Pai is a kind of high-strength polyimide. At present, the development trend is to enhance modification and alloying with other plastics; BMI is a bifunctional compound with maleimide as the active group. It has the advantages of strong body load-carrying capacity, similar fluidity and moldability to typical thermosetting resins, and is basically the same as the processing and molding of epoxy resins. At present, BMI is a hot spot in domestic research and development. In order to improve the application performance of polyimide, polyimide is modified with composites or find out the abnormalities in the chain; Or they can be used to create a few materials. The development and application of polyimide has become a hot spot in the research and development of polyimide for a long time in the future. For example, polyhomoimide filled with graphite or polytetrafluoroethylene under high temperature conditions (>200 ℃) can significantly reduce the friction coefficient, which can be used for automotive thrust washers, high temperature brake pads, windshield wipers, bearings, bushings and washers for aircraft gas turbine engines; Polyimide added with glass fiber or boron fiber is called super strong engineering plastic, which is used to prepare structural components of jet engine; Silicon containing polyimide can endow the material with good solubility, air permeability, impact resistance, weather resistance and adhesion; In addition, there are fluorinated polyimide and so on

Japan's Nissan Chemical Company plans to double its output of polyimide resin used in the manufacture of liquid crystal displays. The company invested about 2billion yen (US $18.4 million) to expand the production capacity of its polyimide resin plant in Chiba to 460 tons/year in the first or second quarter of 2005. In addition, the company plans to spend 1billion yen to increase the output of its microchip material production device in Toyama Prefecture by 60%. Nissan aims to increase the sales of these products by about 50% from 16billion yen in 2003 by 2007. Polyimide resin is a super heat-resistant material, which helps to display high-definition images on LCDs

thermoplastic polyimide, a cutting-edge material developed by Nanjing University of technology and supported by Changzhou Guangcheng New Plastic Co., Ltd., has been successfully developed. The advent of this special engineering plastic has ended the long-term dependence on imports of such products in China and filled the domestic gap. The thermoplastic polyimide not only has excellent mechanical properties, dielectric properties, heat resistance, corrosion resistance, wear resistance and other characteristics, but also overcomes the defects that most polyimides are insoluble and difficult to process, showing good hot processing characteristics. It can be molded by hot molding, extrusion and injection methods, and can be compounded with carbon fiber, glass fiber, polytetrafluoroethylene, graphite and other materials to further improve the tensile, self-lubricating, wear resistance and other properties of the material. This material can be made into film, or molded into pipes, bars, and precision components with complex structures. Therefore, it is an ideal material that can replace metals, ceramics, thermosetting resins, low-temperature thermoplastics, and difficult to machine polyimide under specific conditions. At present, the technology has been fully industrialized and has formed a 200 ton/year device capacity. The thermoplastic polyimide products produced can be used in automotive and aircraft engines, communication instruments, construction machinery, industrial machinery, commercial equipment, electronic appliances and microelectronics, analytical and medical equipment, transmission and textile equipment and other fields, which will promote the upgrading of China's chemical products, so as to improve market competitiveness

polyimide in China has developed rapidly with the development of national defense industry, and its research and application in some fields have reached the world level. The gap with foreign advanced countries is mainly reflected in the small scale. At present, the largest production unit in China is 100 tons/year, and the scale of foreign developed countries is basically 1000 tons; The quality of our products is poor and the performance is unstable, which affects the application; The refinement of products is not enough, and there are few varieties. At present, it is mainly poly (phenylene tetramine) to choose a kind of formamide film with smaller size as much as possible. The application fields are also mainly film and molding plastics, while foreign products have a wide variety, such as film, molding parts, coating, adhesive, enamel, foam and fiber. While developing the existing varieties, China should vigorously develop major resin varieties with large consumption, such as polyetherimide, polybiphenyltetraformimide, thermoplastic polyimide and POLYBISMALEIMIDE. (end)

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