Carbon fiber has the characteristics of light weight, high strength, high modulus, chemical resistance, etc. It is widely used in aerospace, new energy, rail transportation and other fields. Carbon fiber can be divided into polyacrylonitrile (PAN)-based, asphalt-based, viscose-based and so on according to the type of the original filament. Among them, PAN-based carbon fiber dominates due to advantages in production process, raw materials, structure and function. Europe, the United States and Japan have been leading in the research and development of efficient, energy-saving and environmentally friendly production processes and new types of raw fibers for low-cost carbon fibers. The following section mainly introduces relevant innovation cases abroad.
Japan's Mitsui Chemicals Co., Ltd. and Microwave Chemicals Co., Ltd. have established an innovative and environmentally friendly carbon fiber manufacturing base technology, Microwave Heating Technology Carbon MX TM. Microwave-heated fibers are applied to the oxidation process, the most energy-consuming part of carbon fiber production, as well as to the carbonization process. In addition to a more compact production line, the new technology reduces energy consumption by approximately 50 percent and drastically shortens processing times compared to conventional methods. The microwave chemistry pilot line, which is expected to cost €14 million, is expected to have an annual capacity of 30t of PAN precursors and 12.5t of carbon fibers, and operate for 250 days per year, it was revealed.
Plasma chemistry is another energy-saving alternative to carbon fiber manufacturing, the United States 4M Carbon Fiber Company and Oak Ridge National Laboratory jointly developed the 4X technology (formerly known as RMX technology), than the pre-oxidation of three times faster than the rate of unit energy consumption is reduced by 75% and the quality of the carbon fibers is higher. AG Germany and the German Textile and Fiber Research Institute (DTFRI) have jointly developed a new concept and technology for the pre-oxidation of carbon fiber filaments at reduced pressure and in a specific atmosphere. The technology can precisely adjust the atmosphere and oxygen concentration of the pre-oxidation process, and low pressure is the most effective control of the oxygen concentration of the best method, so that the processing time can be reduced by 30%, and due to the process of using less gas, so the cost of energy consumption decreased by 50%.
The patented technology from Deakin University, Australia - licensed from Oak Ridge, Tennessee, USA - also enables rapid oxidation, but not by microwave or plasma heating. It adds a 1- to 2-min pre-stabilization phase with an oxygen-free precursor, which can reduce the subsequent oxidation/stabilization time to 15 min, followed by a 3-min carbonization. A third-party audit of Deakin's 24K fiber test line confirmed its reduced oxidation time and product performance was comparable to Toray's T300 fiber, but did not quite reach the performance of the T700S standard modulus 12K fiber, a benchmark for pressure vessels and some aerospace applications. More accurately, Deakin's fiber exceeds the T700S modulus, but falls short of the 4.9 GPa tensile strength and 2.1% strain to failure. However, the researchers involved say that the cost per kilogram of fiber is reduced by 75% and energy consumption by 70%. Thus, it is of interest for applications where modulus is more important but tensile strength is not as demanding.
The high production costs of common PAN-based carbon fibers and high material costs have created an urgent need for the development of raw materials and manufacturing processes with higher cost-effectiveness, which can further contribute to the development and growth of industrial composite applications. Flávio André Marter Diniz, a graduate of the Institute of Textile Technology (ITA) at RWTH Aachen University in Germany, developed ultrafine polyethylene-based (PE) carbon fibers in his master's thesis "Stabilization and Carbonization Processes in the Production of Ultrafine Polyethylene-Based Carbon Fibers," and won the Hanns Voith Foundation Award for this innovation. Voith Foundation Award for "New Materials". The innovations include a fiber filament diameter of less than 3 μm, which is two to three times thinner than conventional carbon fibers; excellent fiber surface quality, with no detectable structural defects; the use of low-cost PE-based precursors, which is expected to reduce the cost of carbon fiber production by up to 50% in the future; and a reduction of sulfonation time by 25%, which can be widely used in key industries such as wind power, aerospace, and automotive engines.