In twentieth Century 60, the development of the aerospace industry of the polyimide (PI) emerge as the times require, and it is a new engineering plastics containing amide groups, according to the performance of pseudo thermoplastic polyimide, thermoplastic and thermosetting polyimide polyimide. The aromatic heterocyclic structure is very stable with polyimide molecules, which reflects the excellent performance of other polymer materials by the incomparable: heat resistance and low temperature, the biphenyl two anhydride and amine synthesis of benzaldehyde two PI, thermal decomposition temperature can reach 600 ℃, is by far one of the poly high thermal stability in the varieties.At such temperatures, short time basically can maintain the original physical performance, can be used for a long time at 333 ℃, the other at -269 ℃ still not embrittlement; high mechanical strength, tensile strength of benzene type PI film can reach 170Mpa, and biphenyl type can reach 400Mpa, with the increase of temperature, the change is very small; resistance to radiation; dielectric properties; chemical properties of stability, most varieties are not soluble in organic solvents, acid, alkali is stable; in addition, the PI creep resistant ability, excellent friction performance.
Research and development is very active at present global polyimide, polyimide has more than 20 varieties, in 2001 the global consumption of about 25000 tons, mainly manufactures more than about 50, mainly concentrated in the developed countries, Japan, Western Europe and other USA and area, in addition Chinese (including Taiwan), South Korea, Russia is the production of polyimide part of the enterprise. Along with the aerospace, automotive and especially the rapid development of electronic and electrical industry, the miniaturization of electronic components, lightweight, high performance and high reliability requirements, foreign authority predicts the next few years the world demand for polyimide, will increase at an annual rate of about 10%, showing a good development prospects.
Our country almost simultaneous with the world began to research and development of polyimide, polyimide development in our country many varieties, involving anhydride, trimellitic anhydride type, biphenyl two anhydride type, bisphenol A type two anhydride, ether anhydride and BTDA, currently has nearly 20 manufacturers, the annual production capacity is about 900 tons / year, the main production unit with the Jiande City Solver Polyimide Co., Ltd., in 2001 the domestic output of about 400 tons, our country compared with foreign products in many varieties, has a great competitive advantages in terms of price, so our country electrical insulating film market basically is domestic product occupied, and China has already begun to foreign export products.
At present, the thermoplastic polyimide is mainly used to cover oil and gas pump, auto engine parts, electronic / electrical instrument with high temperature socket, connector, the printed circuit board and the hard disk of the computer, integrated circuit chip carrier, aircraft interior cargo system. Polyimide many varieties, but at present the main varieties of polyetherimide (PEI), polyamide imide (PAI) and bismaleimide (BMI) etc.. PEI is currently developing trend is to introduce the two benzene amine structure or other engineering plastic alloy, improve its heat resistance, or with polycarbonate, polyamide engineering plastics alloy to improve the mechanical strength; PAI is a polyimide varieties with high strength, the current development trend is to enhance the modification, as well as with other plastic alloy; BMI bifunctional compounds with maleimide as the active medium, with mobility similar to typical thermosetting resin and moldability, basically the same as the processing and molding of epoxy resin, is the hot point of research and development at home, there are a large number of data and patent reported annual domestic.
In order to improve the application performance of polyimide, polyimide modification, development and application of composite materials and become the research and development of hot spots in quite long time, polyimide, such as poly benzene diimide filled with graphite or PTFE, can significantly reduce the friction coefficient, used in automobile thrust washer, high temperature brake pads, windshield wipers, bearings, bushings and washers for aircraft turbine engine gas; polyimide glass fiber or boron fiber, known as super engineering plastic, used in the preparation of jet engine components; silicon containing polyimide, can give the material good solubility, permeability, impact resistance, weatherability, adhesion; in addition to containing fluorinated polyimide.
Our country is mainly with polyimide our defense industry development has been rapid development, research and application in some areas has reached the world level. But compared with foreign advanced countries there are still large gaps, mainly reflected in small scale, is currently the largest domestic production plant for 100 tons / year, the developed countries is basically a kiloton size; China's product quality is poor, unstable performance, products of different batches, the performance gap is relatively large, effect of application; the most serious is fine the degree of Chinese products is not enough, few varieties, at present mainly in the poly pyromellitic polyimide films based, application fields are mainly film and plastic mold, and used in military field, civil less, and many kinds of foreign products, such as film, plastics, coatings, adhesives, enamel, foam and fiber etc..
Because the polyimide engineering plastics application fields and prospects, especially play a decisive role in national defense construction, thus speeding up the research and application of the polyimide is very important and necessary to. In view of the domestic and foreign development present situation, China should in the development of the existing varieties at the same time, according to the national development of polyetherimide, poly diphenyl tetramethyl imide, thermoplastic polyimides and poly bismaleimide resin products larger dosage.
At present, the synthesis and application of domestic research and development of polyimide is very active, should accelerate the pace of technological transformation, from the synthesis technology and application experience of the existing species, to promote the industrialization of new polyimide materials. Especially to strengthen applied research, such as the modification and the application of composite material technology research and extension. In addition, to strengthen the management, looking to the future, improve product quality, truly cheap Wumart, thereby improving the competitiveness in the international market.