1. What's the use of carbon fibers?
Carbon fiber is a new kind of material with many valuable electrical, thermal and mechanical properties, known as & ldquo; Black Gold & rdquo;. Carbon fibers and graphene, the latest star material, are & ldquo; the same family & rdquo;. At present, carbon fiber has been widely used in many fields, such as aircraft, automotive materials, fan blades, sports goods, medical devices and so on.
Carbon fibers will further expand their application needs, possibly focusing on three major areas: ldquo; air-land wind & rdquo; and
1) In aerospace, with the rising international oil price and the higher requirements for flight time and reliability of aircraft, carbon fibers gradually enter the field of aircraft structural materials, challenging the unified status of aluminum alloy;
2) The development direction of the new generation of automobiles is to ensure safety and lightweight at the same time. The density of carbon fibers is lower than that of carbon steel and aluminium alloy, and the strength and modulus of carbon fibers are higher than that of steel. Therefore, carbon fibers composite is the most effective method.
3) The use of carbon fibers instead of traditional glass fibers to make wind turbine blades can improve the stiffness of the blades, reduce the quality of the blades and improve the output power of the fan. Moreover, the anti-fatigue performance of carbon fiber blades is superior, and the electrical conductivity of carbon fiber blades can also avoid the corrosion and lightning strike of blades in special climate. Carbon fibrillation is the development direction of large fan blades at present.
3) In the field of medical equipment, carbon fiber is a very good material for medical panel production because of its good X-ray transmission ability.
2. Productivity: Global demand for carbon fibers continues to grow, while domestic carbon fibers are still lagging behind.
Global carbon fiber production capacity in 2014 was about 129 million tons, an 11% increase over 2013. At a 10% growth rate, global carbon fiber production capacity reached 149,900 tons in 2015. At present, the vast majority of the market share is divided up by American and Japanese enterprises. In the small tow market, Toray, Tohoku and Mitsubishi account for 54% of the market share. In the large tow market, Hexcel and SGL in the United States account for 73% of the global share and are in the leading position. At present, the total production capacity of domestic carbon fibers reaches 15,000 tons, and there are about 30 enterprises, but all of them are concentrated in low-value-added carbon fibers (small tows). High-modulus and high-strength carbon fibers are still in the technical research in China, which is far from Japan and the United States.
Due to the backwardness of production technology and neglect of high-quality production of polyacrylonitrile, the production cost of most domestic manufacturers remains high. At present, the price of domestic T300 grade carbon fibers has reached the price of imported Toray T700 grade carbon fibers. In addition, in recent years, after China has been able to produce a grade of carbon fibers in a steady batch, the sales prices of Toray, Dongbang and Hexcel in China have dropped dramatically once. For example, in 2010, the T300 grade carbon fibers at 12K will be 240,000 yuan per ton, and in 2012 it will be 120,000 yuan per ton. Now the price of T700 grade carbon fibers has begun to decline steadily. This is also the main reason why China's carbon fiber enterprises continue to lose money. Similar phenomena have occurred in the field of aramid 1313.
Another reason for China's backwardness is the backwardness of equipment. Previous research and development costs and production line equipment have also been greatly depreciated and amortized, so the cost of domestic carbon fiber enterprises is much higher than that of foreign ones.
At present, the domestic enterprises that can have T700 industrialization production technology are: Zhongfu Shenying (parent company China building materials), Jiangsu Hengshen (new third board listing), Weihai Development, Jilin Shenzhou (mainly military carbon fibers, parent company China Steel International), Jiangsu Aeronautics (Beijing City Construction had considered acquisition, terminated in May 2015). The T700 and above products of these enterprises are still under application assessment. It usually takes at least two years.
3. About Different Raw Material Bases
According to the raw materials, it can be divided into polyacrylonitrile-based carbon fibers, asphalt-based carbon fibers, viscose-based carbon fibers, phenolic-based carbon fibers and vapor-grown carbon fibers. Among them, because the preparation method of acrylonitrile is relatively simple, and the flexural and compressive properties of the precursor products are very excellent, so it is the mainstream of the carbon fiber market, accounting for more than 90%.
category
tensile strength
GPa
Young modulus
GPa
density
G/cm3
Elongation at break
%
Polyacrylonitrile group
2.7-6.3
230-588
~1.8
0.6-1.2
Asphalt base
One point six
Three hundred and seventy-nine
One point seven
One
rayon
2.1-2.8
414-552
Two
Zero.7
Nbsp; 4. on the size of tows
The size of tows is one of the important indexes of carbon fibers, that is, the number of roots per bundle of carbon fibers. Usually, the number of carbon fibers per bundle is more than 48000 (referred to as 48K) roots, which is called large bundle carbon fibers, including 60000 (60K), 120000 (120K), 180000 (180K), 320000 (320K), 360000 (360K) and so on. And 1000, 3000, 6O00, 12000 and 24000 are small tow carbon fibers.
Compared with the small tow, the disadvantage of the large tow is that it is not suitable to deploy the tow when making sheet and other structures, which leads to the increase of single layer thickness and is not conducive to the structural design. In addition, there are more phenomena such as adhesion and breakage of large tow carbon fibers, which will affect the strength and stiffness, reduce the performance and increase the dispersion of the performance. Aircraft and spacecraft generally only use small tow carbon fibers, so small tow carbon fibers are also known as & quot; space class & quot; carbon fibers, large tow carbon fibers are called & quot; industrial class & quot; carbon fibers, currently used in automobiles, wind installations, general industry and other fields.
However, the production cost of large tow is lower than that of small tow (small tow is expensive). With the progress of production technology and the familiarity with the structure of carbon fiber materials, large tow carbon fibers are increasingly used in areas where reliability requirements are stringent.
5. On T and M Series
Carbon fibers are classified into high strength, high modulus, super high strength and super high modulus series. T is the high strength series.M is a high modulus series, the more rigid it is.
Main products: carbon fiber strength: T300< T600< T700< T800< T1000
Main products tensile modulus: M30< M40< M46< M50< M60< M65
6. Production Technology
7. Carbon Fiber Composites
Carbon fibers seldom enter the application field directly. They are mostly composited with resins, metals, ceramics and other materials as matrix to form structural materials with qualified strength, modulus and other comprehensive indicators, i.e. composite materials. At present, resin matrix composites (CFRP) are widely used, including resin transfer moulding (RTM), injection moulding and pultrusion moulding.
