The domestic road of carbon fiber
Interview with Professor Xu Lianghua, Professor of carbon fiber, Beijing University of Chemical Technology
Xu Lianghua, director of carbon fiber engineering research center of North China, deputy director of Key Laboratory of carbon fiber and functional polymer education, director of carbon fiber and composite Research Institute, director of carbon fiber and functional polymer. T700 grade carbon fiber preparation technology and products have been invented, which have supported the development of China's major models, first realized the technological breakthrough of T800 grade high strength medium mold carbon fiber, filled the domestic gap, developed the high performance carbon fiber localization technology such as M40J, M55J and so on, and won the national scientific and technological progress two awards in 2014.
On 8 Q:5, the group of experts from the high technology center of the Ministry of science and technology accepted the technical acceptance of the topic "Research on key technology of polyacrylonitrile carbon fiber graphitization" on the 863 subject of the Ministry of science and technology. Please briefly introduce the significance of the subject to us.
A: this project is mainly aimed at the technology and equipment of Dongli M55J high strength and high modulus carbon fiber materials. M55J is the main material of satellite, which has always depended on foreign imports. The acceptance of this project has two important significance: first, the process technology is domestically made. From the previous experience, the preparation of carbon fiber follows the laws of mutual restraint of strength and modulus, the modulus will decrease and the modulus increases the strength. It will fall. It is a challenge to combine the two kinds of structures from the disorderly graphite to the graphite like, mainly graphite structure, with high modulus and poor strength. Under the support of the 973 Plan of the Ministry of science and technology in 2010, the basic science was started around this problem, and the structure model of high strength and high modulus carbon fiber was put forward. The rationality of the model was verified through the technology of M40J. We have been guiding our key technology research with this model. The two is the localization of equipment. The key technology of high modulus fiber is high temperature graphitization. The temperature is as high as 2500 degrees Celsius. The stove has always been our weakness. In this project, the cooperative enterprise is also very experienced. The stove is still repeatedly discussed, designed, modified, and finally verified. Technology and equipment have been nationalized, and their dependence on foreign countries has been reduced. Facing blockade control, they will not be controlled by others.
The highlight of this project is to integrate the users (Beijing satellite manufacturing factory) together and verify the finished products in time to the application department. Domestic carbon fiber is facing such a problem. Carbon fiber has excellent performance. However, the gap between the composite materials is large, which requires a very long running in period. T300, T700, T800 compared with M55J, the cost is still lower, the verification 3~5 is still within the scope, but the higher cost of M55J, for a long time assessment, verification, the expenditure will be very large. At the beginning of the project, we combine the users with the subject. After 3 years, we have made the fiber to meet the requirements of the key technology, equipment and engineering applications. The performance of the composite structure has also reached the design requirements, saving time, reducing cost and improving efficiency. Research and use of cooperation model is very worthy of reference.
Q: at present, the market leading position is PAN based carbon fiber. Please give us a brief introduction to the basic research and industrialization of the carbon fiber.
A:PAN based carbon fibers are called polyacrylonitrile carbon fibers. There are 4 types of carbon fibers in all, one of which is the main category, accounting for about 90% of the carbon fiber products. Foreign research began in 1960s, we started in 1970s, this start gap is not big, but the first 35 years have been hovering, only nearly 15 years in rapid development. Why is it wandering? It is the lack of basic research. Most of the research institutes of enterprises or enterprises engaged in fiber research are devoted to solving engineering problems.
Now the domestic mainstream technology two methyl sulfoxide method is our breakthrough in 2000. Before this, we did the basic research of 2~3 years, regard carbon fiber as polymer material, return to the basic scientific problem, follow the objective law of polymer material, simplify the complex problem simply. Since then, we have found the right direction and developed rapidly. The past 35 years are always exploring. This method can not work, nor will it be in that direction. The gap with foreign countries is bigger and bigger. In 2002, we built the first line of engineering. In 2006, the first industrial line was built in China. In 18 years now, the gap between the key technology and foreign countries is narrowing.
There are still 5 generations in the industry. The industrial system is not perfect. By the end of 2017, the theoretical capacity was 26000 tons, the kiloton line had 11, 100~400 ton line 17, 500 ton line 9, but our capacity release rate was 29%, the international average reached 65%, and Dongli could reach 70%. The low productivity release rate reflects the low technology maturity of our industry, the fundamental reason is that the system construction is not perfect, one of the core problems involved is the equipment. China's carbon fiber industrialization equipment is from the introduction of the introduction, domestic digestion, absorption, and innovation do not do well, leading to production is often the process to meet equipment, so there will be problems, the introduction of the introduction of the time is not in accordance with the production line, but in accordance with the installation of the equipment, self-assembly construction, supplier guarantee single If the equipment meets the technical requirements, it is impossible to build the industrial line. We have no more experience in industrialization, and we can not put forward the industrial equipment needs around the technology, so that many equipment production capacity can not reach the design goal.
Such equipment as tens of tons to 100 tons can be done domestically, but there are still many problems in the thousand ton scale. The domestic manufacturing of the carbon fiber industrial equipment is similar to the equipment in other industries. It is mainly dependent on experience and is still lacking in the use of simulation and simulation technology. This leads to the requirement for the temperature field and the air flow field in the carbon fiber production equipment in the static condition, but the dynamic environment of production and the "two field" wave are reached. The movement is relatively large, which leads to a large fluctuation in the quality of carbon fibers produced. There are also restrictions on equipment abroad, especially in the United States, which limits the temperature of equipment. Germany is a little better, working with Chinese enterprises to produce in China, as long as it is not used for high-end carbon fiber preparation, the conditions are relatively loose. The United States needs more than 1800 degrees of license.
Domestic equipment I think the main problem is still lack of design simulation, the introduction, digestion, imitation of such reverse thinking may be implemented difficult or relatively large, because the foreign product update is faster, the level is also improving. For example, the pre oxidation equipment needs gas circulation. Different fiber types and different specifications adopt different circulation modes. Because we will not design, we can only rely on the introduction of equipment recycling mode, which is relatively passive. The development of carbon fiber requires attention to equipment, not what we think can be bought if I have money. The prototype of Dongli equipment is also external processing, but it will be reformed two times according to its own technology, equipment manufacturers are not allowed to participate, and there are almost no two transformation in China, import equipment can not move, some enterprises will have a little transformation.
Observation of domestic carbon fiber enterprises, all of their own relatively strong capacity of industrialization is better, otherwise vice versa. This phenomenon is very obvious, so we advocate that carbon fiber enterprises must have their own equipment capabilities, which may take a long time. It is difficult for China to cultivate its own equipment manufacturers. The equipment of the United States and Germany is facing the world, the market is large, and the market of the equipment manufacturers in China may only be China, and our equipment is difficult to go out. After all, the market is limited. Enterprises specializing in equipment are not interested in the field of carbon fiber; interested in the intervention, the initial investment will be higher, now the cost of an industrialization line is about 150 million, the investment in development needs at least 2 hundred million, and it is difficult to see the benefit in the short term. It may need to build dozens of lines to produce returns, and there is not that at home. The big market, so the situation is more embarrassing. The technological R & D, storage and conditional support of such key strategic materials will not work alone.
Q: what are the challenges of the wide application of domestic carbon fiber in high-end fields? How should high quality and low cost be achieved?
A: at present, the domestic large carbon fiber enterprise Malaya car can guarantee the quality stability in the high-end field. What we are talking about is unstable quality. The deep level is the fluctuation in the use process, that is, the use of technology. First, the fiber made of composite materials, the application department will mark foreign products, predominant and foreign fiber skillfully, the qualitative summary is not good, in fact, there are many deep problems to be excavated. Two, the strength transfer power is low, the fiber performance is similar to the standard foreign products, but the performance difference of the composite material is obvious. Basically, each carbon fiber will encounter these 2 problems, and in the ordinary discussion, we also explore these problems. The fundamental reason is that the fine operation in the process of fiber preparation is not enough. In a bunch of fiber theory, each fiber is very regular, but our fiber will be intersecting, and the intersecting fibers are not completely arranged in 0 degrees, and the performance will be reduced. So now, the requirements for fine preparation are strengthened, the preparation of fiber is considered from the application end, and the problem is slowly grasped. The pulse should be faster.
In 2002, there were only 3 R & D units engaged in carbon fiber in China, including mountain, North and Shanxi coalification, and some of the Donghua University, but mainly made of gelatin carbon fiber. In 2008, I helped to build the carbon fiber Laboratory of Ningbo Institute of materials of the Chinese Academy of Sciences, and the research unit turned into 4. Up to now, fewer than 4 key technologies have been studied. It is easy to see that R & D strength is shrinking. I often think about this problem, and also put forward a written proposal, our basic research needs to be strengthened, the R & D team should be expanded, there are 3~5 R & D units, moderate competition and cooperation interaction is a good thing, if the sole development, the direction may be skew. Our research and development achievements are in the implementation of industrialization, but I do not do the industrialization, and the division of labor and cooperation with enterprises, I concentrate on technology research and development, after all, the energy is limited. Carbon fiber is a very complex material, and the laboratory also has the characteristics of industrialization. It is a narrow version of the industrial line. It is difficult to get to the introduction without 3~5 years of in-depth study.
Domestic carbon fiber is relatively high cost and high cost. We think it is not only an economic issue, but a deep technical problem. Expensive energy and expensive equipment are only one of the factors, most of which are technical factors. Production capacity is not released, equipment technology is not in good condition, the proportion of sizing agent is high, fiber passing rate is low, and quality can not meet the application requirements are all technical problems. High quality and low cost can be achieved through reasonable technical means. For carbon fiber we put forward the price of $10 /kg in 2030, and the previous time Boeing's Chinese experts visited, and they put forward a target of 5 dollars / pounds, the goal.
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