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Composite materials are materials made of two or more different substances combined in different ways, which can bring into play the advantages of a variety of materials to overcome the defects of a single material, and expand the scope of application of materials. As composite materials have light weight, high strength, easy processing and molding, excellent elasticity, chemical resistance and good weather resistance, etc., they have gradually replaced wood and metal alloys, and are widely used in aerospace, automotive, electrical and electronic, construction, fitness equipment and other fields, and in recent years have been rapid development.
With the development of science and technology, resin and glass fiber in the technology continues to progress, manufacturers of manufacturing capacity generally improve, making the price of glass fiber reinforced composite materials cost has been accepted by many industries, but the strength of the glass fiber reinforced composite materials is not enough to match the metal. Therefore, carbon fibers, boron fibers and other reinforced composite materials have been introduced, so that the polymer composite materials family is more complete, has become a necessary material for many industries. At present, the world's annual output of composite materials has reached more than 5.5 million tons, the annual output value of more than 130 billion U.S. dollars, if Europe and the United States of America's military aerospace high-value products into account, its value will be even more amazing. From a global perspective, the world production of composite materials is mainly concentrated in Europe and the United States and East Asia. In recent years, Europe and the United States composite materials production and demand have continued to grow, while Japan in Asia due to the economic downturn, the development of a slower, but China, especially in mainland China's rapid development of the market. According to the world's leading composite materials manufacturer PPG statistics, in 2000, Europe's global share of composite materials is about 32%, the annual output of about 2 million tons. At the same time, the United States composite materials in the 1990s, the average annual growth rate of about two times the growth rate of U.S. GDP, reaching 4% to 6%. 2000, the annual production of U.S. composite materials amounted to about 1.7 million tons. In particular, the rapid increase in composite materials for automobiles has led to the re-emergence of U.S. automobiles in the global market. The development of composite materials in Asia in recent years is closely related to the overall changes in the political economy, and the share of each country has changed a lot. Overall, composites in Asia will continue to grow, with a total production of about 1.45 million tons in 2000, and an expected total production of 1.8 million tons in 2005.
From the application, composite materials in the United States and Europe are mainly used in aerospace, automotive and other industries. 2000 U.S. automotive parts of the amount of composite materials amounted to 148,000 tons, the amount of European automotive composite materials to 2003 is estimated to be up to 105,000 tons. In Japan, composite materials are mainly used in residential construction, such as sanitary equipment, such products in 2000, the amount of 75,000 tons, automotive and other areas of the amount of only 24,000 tons. However, from a global perspective, the automotive industry is the largest user of composite materials, the future development potential is still very large, there are many new technologies being developed. For example, in order to reduce engine noise, increase the comfort of the car, is focusing on the development of two layers of cold rolled plate adhesive thermoplastic resin between the vibration damping steel; to meet the engine to high-speed, supercharged, high load direction of the development of the requirements of the engine pistons, connecting rods, axle shaft has begun to apply the metal matrix composite materials. In order to meet the requirements of automobile lightweight, there will be more and more new composite materials will be applied to the automobile manufacturing industry. At the same time, with the increasing attention to environmental issues in recent years, polymer composite materials to replace the application of wood has been further promoted. For example, with plant fibers and waste plastic processing composite materials, in North America has been used as a large number of trays and boxes to replace wooden products; and biodegradable composite materials have also become the focus of domestic and foreign development and research.
In addition, nanotechnology has gradually attracted people's attention, and the research and development of nanocomposite materials has become a new hot spot. To nano-modified plastics, can make the plastic aggregation state and crystallization morphology change, so that it has a new performance, in overcoming the traditional material rigidity and toughness is difficult to be compatible with the contradiction at the same time, greatly improving the comprehensive performance of the material.
Reinforcement materials of resin matrix composites
The reinforcing materials used in resin matrix composites are mainly glass fibers, carbon fibers, aramid fibers, ultra-high molecular weight polyethylene fibers and so on.
1, glass fiber
Currently used in high-performance composite materials, glass fiber is mainly used in high-strength glass fiber, quartz glass fiber and high silica glass fiber. Due to the high strength glass fiber cost-effective, so the growth rate is also relatively fast, the annual growth rate of more than 10%. High-strength glass fiber composites are not only used in military applications, in recent years, civil products are also widely used, such as bulletproof helmets, bulletproof clothing, helicopter wings, early warning aircraft radomes, a variety of high-pressure pressure vessels, civil aircraft straight, sporting goods, various types of high-temperature products, as well as recent reports of excellent performance of the tire cord and so on. Quartz glass fiber and high silica glass fiber belongs to the high-temperature glass fiber, is a more ideal heat-resistant fire-resistant materials, with its reinforced phenolic resin can be made into a variety of structural high-temperature-resistant, abrasion-resistant composite parts, a large number of applications in rockets, missiles, heat-resistant materials. So far, China has been practical high-performance resin-based composites with carbon fiber, aramid fiber, high-strength glass fiber in the three major reinforcing fibers, only high-strength glass fiber has reached the international advanced level, and has independent intellectual property rights, the formation of a small-scale industry, the current stage of the annual output of up to 500 tons.
2, carbon fiber
Carbon fiber with high strength, high modulus, high temperature, conductive and a series of properties, the first in the field of aerospace has been widely used in recent years in sports equipment and sporting goods are also widely used. It is predicted that civil construction, transportation, automotive, energy and other fields will be a large-scale use of industrial-grade carbon fiber. 1997 ~ 2000 years, the astronautics with carbon fiber annual growth rate is estimated at 31%, while the annual growth rate of industrial carbon fiber is estimated to reach 130%. The overall level of carbon fiber in China is still relatively low, equivalent to the level of foreign countries in the mid- and late seventies, with a gap of about 20 years. The main problems of domestic carbon fiber is not very stable performance and large coefficient of dispersion, no high-performance carbon fiber, a single species, specifications are not complete, the continuous length is not enough, without surface treatment, the price is high and so on.
3, aramid fibers
Since the 1980s, the Netherlands, Japan, the former Soviet Union has also carried out the development of aramid fibers. Japan and Russia's aramid fiber has been put on the market, the annual growth rate has reached about 20%. Aramid fiber specific strength, high specific modulus, so it is widely used in aerospace field of high-performance composite parts (such as rocket engine casing, aircraft engine nacelle, fairings, rudders, etc.), ships (such as aircraft carriers, nuclear submarines, yachts, lifeboats, etc.), automobiles (such as tire cords, high-pressure hoses, friction materials, high-pressure cylinders, etc.), as well as heat-resistant transport belts, sports equipment and so on.
4, ultra-high molecular weight polyethylene fiber
Ultra-high molecular weight polyethylene fiber specific strength in a variety of fibers in the first place, especially its resistance to chemical reagent erosion performance and anti-aging performance is excellent. It also has excellent high-frequency sonar permeability and seawater corrosion resistance, many countries have used it to manufacture ships with high-frequency sonar deflector, which greatly improves the ship's ability to detect mines, mine clearance. In addition to the military field, in the automobile manufacturing, shipbuilding, medical equipment, sports equipment and other areas of ultra-high molecular weight polyethylene fiber also has a broad application prospects. The fiber has attracted great interest and attention from the developed countries in the world.
5, thermosetting resin-based composites
Thermosetting resin-based composites refers to thermosetting resins such as unsaturated polyester resins, epoxy resins, phenolic resins, vinyl ester resins, etc. for the matrix, glass fibers, carbon fibers, aramid fibers, ultra-high molecular weight polyethylene fibers, etc., for the reinforcing material made of composite materials. Epoxy resin is characterized by excellent chemical stability, electrical insulation, corrosion resistance, good adhesive properties and high mechanical strength, widely used in chemical industry, light industry, machinery, electronics, water conservancy, transportation, automobiles, home appliances and aerospace and other fields. 1993 world production capacity of 1.3 million tons of epoxy resins, in 1996 increased to 1.43 million tons in 1997 to 1.48 million tons in 1999 to 1.5 million tons in 2003 to 1.5 million tons. In 1999, it was 1.5 million tons, and in 2003, it reached about 1.8 million tons. China began to study epoxy resin in 1975, according to incomplete statistics, there are about 170 epoxy resin production enterprises in China, with a total production capacity of more than 500,000 tons, and the equipment utilization rate is about 80%. Phenolic resin has the characteristics of heat resistance, abrasion resistance, high mechanical strength, excellent electrical insulation, low fuming and excellent acid resistance, etc., thus it is widely used in various fields of the composite materials industry.In 1997, the global production of phenolic resin was 3 million tons, of which the United States was 1.64 million tons. China's output was 180,000 tons, and 40,000 tons were imported. Vinyl ester resin is a new type of thermosetting resin developed in the 1960s, which is characterized by good corrosion resistance, good solvent resistance, high mechanical strength, high elongation, good adhesion with metals, plastics, concrete and other materials, good fatigue resistance, good electrical properties, heat aging, low shrinkage rate of the curing can be ambient curing can also be heated curing. Nanjing Jinling DSM Resin Co., Ltd. introduced the Dutch Atlac series of strong corrosion-resistant vinyl ester resin, has been widely used in storage tanks, containers, pipelines, etc., and some varieties can be used for waterproofing and hot pressing molding. Ltd., Shanghai Xinhua Resin Factory, Nantong Mingjia Polymer Co., Ltd. and other manufacturers also produce vinyl ester resins.
Before 1971, China's thermosetting resin-based composites industry is mainly military products, after the 1970s began to shift to civilian use. From 1987, around the introduction of a large number of foreign advanced technology such as pool kiln drawing, short-cut felt, surface felt production line and a variety of grades of polyester resin (U.S., Germany, the Netherlands, Britain, Italy, Japan) and epoxy resin (Japan, Germany) production technology; in the molding process, the introduction of the winding pipe, tank production line, pultrusion process production line, SMC production line, continuous plate unit, resin transfer molding (RTM) molding machine, injection molding technology, resin injection molding machine, resin production line. In terms of molding technology, the introduction of winding pipe production line, tank production line, pultrusion process production line, SMC production line, continuous plate making unit, resin transfer molding (RTM) molding machine, injection molding technology, resin injection molding technology and fishing rod production line, etc., has formed a complete industrial system from research, design, production and raw materials supporting, as of the end of 2000, China's thermosetting resin-based composites production enterprises amounted to more than 3,000, there have been 51 through the ISO9000 quality system certification, with a variety of more than 3,000 kinds of products, with a total production of 730,000 tons per year, ranking The total output reaches 730,000 tons/year, ranking the second place in the world. The products are mainly used in construction, anticorrosion, light industry, transportation, shipbuilding and other industrial fields. In construction, there are internal and external wall panels, transparent tiles, cooling towers, air-conditioning covers, fans, glass fiber reinforced plastic water tanks, sanitary ware, purification tanks, etc.; in petrochemical industry, it is mainly used in pipelines and storage tanks; in transportation, there are mainly body, hood, bumper and other accessories in automobiles, compartment panels, doors, windows and seats, etc., and in boating, there are mainly hovercrafts, lifeboats, reconnaissance boats and fishing boats, etc.; in the field of machinery and electrical appliances, such as roof fans, axial fans, and other products, there are more than 3,000 kinds of products in the world. and electrical fields such as roof fans, axial fans, cable bridges, insulating rods, integrated circuit boards and other products have a considerable scale; in the aerospace and military fields, light aircraft, tail, satellite antennae, rocket nozzles, bullet-proof panels, bullet-proof vests, torpedoes, etc. have made a major breakthrough.
Thermoplastic resin matrix composites
Thermoplastic resin matrix composites were developed in the 1980s, mainly long fiber reinforced pellets (LFP), continuous fiber reinforced prepreg tape (MITT) and glass fiber mat reinforced thermoplastic composites (GMT). According to the different requirements of use, the resin matrix mainly includes thermoplastic engineering plastics such as PP, PE, PA, PBT, PEI, PC, PES, PEEK, PI, PAI, etc., and the types of fibers include all possible fiber varieties, such as glass fiber, carbon fiber, aramid fiber and boron fiber. With the continuous maturation of thermoplastic resin matrix composites technology and the advantages of recyclable, this variety of composite materials development faster, thermoplastic resin matrix composites in developed countries in Europe and the United States has accounted for more than 30% of the total amount of resin matrix composites.
High-performance thermoplastic resin matrix composites to injection parts mostly, matrix to PP, PA-based. Products include pipe fittings (elbows, tees, flanges), valves, impellers, bearings, electrical appliances and automotive parts, extrusion molding pipes, GMT molded products (such as Jeep seat brackets), automotive pedals, seats, and so on. Applications for glass fiber reinforced polypropylene in automobiles include ventilation and heating systems, air filter housings, transmission covers, seat frames, fender gaskets, drive belt protectors, and more.
Talc-filled PP has high rigidity, high strength, excellent heat aging resistance and cold resistance. Talc-filled PP has important applications in the interior decoration, such as used as ventilation system parts, instrument panels and automatic brake control bar, such as the United States HPM company with 20% talc-filled PP made of honeycomb structure of the sound-absorbing ceilings and sedan window lifter coil drum shell.
Mica composite materials have high rigidity, high heat distortion temperature, low shrinkage, low deflection, dimensional stability and low density, low price, etc., the use of mica/polypropylene composite materials can be made of automotive dashboards, headlamps, protective rings, fender covers, door guards, motor fans, blinds and other parts, the use of the material's damping can be made of audio parts, the use of shielding can be made of storage battery The use of the material damping can be made sound parts, the use of its shielding can be made battery box.
China's thermoplastic resin-based composites research began in the late 1980s, the last decade has made rapid development, the output reached 120,000 tons in 2000, accounting for about 17% of the total output of resin-based composites, the matrix material used is still PP, PA-based, reinforcing materials to glass fiber-based, a small amount of carbon fiber, thermoplastic composites failed to have a major breakthrough, and there is still a significant gap with the developed countries. There is still a gap between the thermoplastic composites and the developed countries.
China's composite materials development potential and hot spots
China's composite materials development potential, but to deal with the following hot issues.
1, composite material innovation
Composite material innovation including composite material technology development, composite material process development, composite material product development and composite material application, specifically to seize the resin matrix development and innovation, innovation in the development of reinforcing materials, innovation in the development of the production process development and innovation in the development of the application of products. By 2007, Asia accounted for the proportion of the world's total sales of composite materials will increase from 18% to 25%, the current per capita consumption in Asia is only 0.29kg, while the United States for the 6.8kg, the Asian region has great potential for growth.
2, polyacrylonitrile-based fiber development
China's carbon fiber industry is developing slowly, from the CF development review, characteristics, the domestic carbon fiber development process, China's PAN-based CF market overview, characteristics, "Tenth Five-Year Plan" scientific and technological research, the development of polyacrylonitrile-based fibers are both the need and the possibility.
3, glass fiber structure adjustment
More than 70% of China's glass fiber for reinforcing substrate, in the international market has a cost advantage, but in the varieties of specifications and quality with the advanced countries there is still a gap between the need to improve and develop the yarn, woven fabrics, nonwoven mats, braided fabrics, sewing fabrics, composite felts, and promote close cooperation between the two industries of fiberglass and fiberglass steel, to promote the new development of glass fiber reinforced materials. The new development of materials.
4, the development of energy, transportation composites market
First, clean, renewable energy composites, including wind power composites, flue gas desulfurization devices with composite materials, power transmission equipment with composite materials and natural gas, hydrogen high-pressure containers; the second is the automobile, urban rail transit composites, including automobile bodies, frames and car body coverings, rail transit body, doors, seats, seats, and other materials. body, doors, seats, cable channels, cable racks, grills, electrical boxes, etc.; Third, composite materials for civil airliners, mainly carbon fiber composites. Thermoplastic composites account for about 10%, and the main products are wing parts, vertical tail, nose cowl and so on. China's next 20 years need to add 661 new regional aircraft, will form a large civil aviation airliner industry, composite materials can be built into a new industry to match; four is the boat with composite materials, mainly for yachts and fishing boats, yachts as a high-level entertainment consumer durables in Europe and the United States there is a large market, due to the decline in China's fish resources, the fishing boat, although the development of the slow, but composite materials, but the unique advantages of the space is still the development of the space.
5, fiber composites infrastructure applications
Domestic and foreign composite materials in bridges, houses, roads in a wide range of basic applications, compared with traditional materials have many advantages, especially in bridges and in the house reinforcement, tunneling, and large-scale storage silo repair and reinforcement in the market is broad.
6, composite materials integrated treatment and regeneration
Focus on the development of physical recovery (crushing recovery), chemical recovery (thermal cracking) and energy recovery, strengthen the technical route, integrated treatment technology research, demonstration production line construction, regeneration and utilization of research, and vigorously expanding the recycled materials in gypsum, pultruded products in the application, as well as in the SMC / BMC molded products application in gypsum, application in pultruded products and application in SMC/BMC molded products and typical products.
The high-performance resin matrix composites technology of the 21st century is to give the composite material self-repairing, self-decomposition, self-diagnosis, self-made function as one of the intelligent materials. Focus on the development of high stiffness, high strength, high humidity and heat environment used in the composite materials, the construction of materials, molding and processing, design, inspection of the integrated material system. Organizational system will be alliance and grouping, which will more fully utilize the resources of all parties (technical resources, material resources), closely linked to the advantages of all parties in order to promote the further development of the composite materials industry.