Reporter | Hou Ruining
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The "king of new materials" - carbon fiber has added new application scenarios in China.
On February 11, Interface News learned from the Sinopec Information Office that the carbon fiber independently developed and produced by Sinopec Shanghai Petrochemical was successfully applied to the "Bay Area Blue" high-speed train of Guangzhou Metro Line 18.
According to the data provided by Sinopec, the performance of the train head cover using carbon fiber composite materials is fully in line with the operating conditions, and the weight can be reduced by up to 35%-40% compared with the aluminum alloy material of the same module, which effectively helps the train to reduce weight and speed.
Guangzhou Metro Line 18 is the first all-underground metro line in China with a speed of 160 kilometers per hour, and is known as the fastest subway in the Guangdong-Hong Kong-Macao Greater Bay Area. The "Bay Area Blue" train, which is responsible for the operation task, is the first subway train in China to use carbon fiber composite materials for the hood.
Carbon fiber is a high-strength new fiber material with a carbon content of more than 95%, the quality is a quarter of steel, the strength is 7-99 times that of steel, corrosion resistance, known as the "king of new materials" or "black gold".
Carbon fiber technical barriers are relatively high, and only a few developed countries such as Japan and the United States currently own and master, especially large tow carbon fiber, most of which rely on imports, and long-term supply exceeds demand.
China began to conduct carbon fiber research in the 1960s and 1970s, entered a new stage of development in 2000, and entered a rapid development stage in 2007, and a number of carbon fiber production enterprises have emerged.
At present, domestic production of carbon fiber enterprises, including Zhongjian Technology (300777.SZ), Zhongfu Shenying Carbon Fiber Co., Ltd., Hengshen Co., Ltd. (832397.NQ), Shanghai Petrochemical (600688.SH), Guangwei Composite (300699.SZ) and Jilin Chemical Fiber Group.
Shanghai Petrochemical is one of the earliest enterprises in China to develop carbon fiber and carry out industrial production.
Shanghai petrochemical carbon fiber production workshop. Image source: Sinopec
In 2007, Sinopec began the research and development and industrialization of PAN-based carbon fiber, and Shanghai Petrochemical was responsible for the project construction. In November 2008, the pilot plant was completed, and in March 2009, 12K prototype wire was developed. 1K represents 1,000 silk in a bundle of carbon fiber, and 12K means 12,000 silk in a bundle of carbon fiber.
In September 2012, the first phase of The Carbon Fiber Project of Shanghai Petrochemical was put into operation, with an annual production capacity of 3,000 tons of polymers, 1,500 tons of raw silk and 500 tons of carbon fiber. The project adopts the unique domestic sodium thiocyanate (NaSCN) wet process complete set of technology, with independent intellectual property rights.
In May 2021, Shanghai Petrochemical's carbon fiber production line with an annual output of 1,000 tons was completed and put into operation. The second phase of the project is under construction, and the entire project will produce 3,000 tons of raw silk and 1,500 tons of carbon fiber per year.
Carbon fiber and masks are "of the same origin", and the raw materials are petroleum.
According to Sinopec, after the oil is extracted, it enters the refinery and is distilled by a normal pressure reducing device to extract components such as naphtha. Naphtha is sent to an ethylene cracking furnace at a temperature of 700-900 degrees Celsius to crack it into propylene.
When propylene is mixed with ammonia and oxygen, under the action of a catalyst, the oxidation reaction of ammonia will occur, and the raw material of carbon fiber - acrylonitrile is obtained. Acrylonitrile monomers undergo a polymerization reaction and are continuously joined together to form a long chain of polyacrylonitrile macromolecules with a spiral structure.
These long chains curl together to form the polymer polyacrylonitrile. A special solvent is then added to the polyacrylonitrile, and the strands of macromolecular molecules entangled together become flowing spinning liquids.
Through mechanical shearing and pipeline transportation, these macromolecules are gradually arranged in an orderly manner, and the spinning fluid is extruded at high speed from the spray holes of the spinneret and solidified in a special solution. After a series of mechanical stretches, a dense and regular white filament is formed.
After continuous processes such as oxidation and high and low temperature carbonization, the color of the white primary silk changes from white to yellow, and then from yellow to black, and the fiber becomes thinner and thinner, and finally forms a "black gold" carbon fiber.
Carbon fiber can be divided into small tow and large tow according to the number of fibers. Carbon fibers with a tow number of less than 24K are generally called small tows, and large tows above 24K.
Carbon fiber. Image source: Sinopec
According to a research report released by Theo Carbon Fiber, the global carbon fiber market size in 2020 is 2.615 billion US dollars. In downstream applications, aerospace accounted for the highest proportion of 37.7%; in the three major carbon neutral battlefields of wind power, photovoltaic and hydrogen energy, carbon fiber was used in wind power blades, carbon carbon composites and pressure vessels.
According to Changjiang Securities, China's carbon fiber market will grow from 6.3 billion yuan in 2020 to 16.4 billion yuan in 2025 and further to 43.3 billion yuan by 2030.
Shanghai Petrochemical is the only enterprise in China's petrochemical system to develop and produce carbon fiber, and it is also the first enterprise in China to take the lead in breaking through the industrialization technology of 48K large tow carbon fiber.
The biggest advantage of 48K large tow is that under the same production conditions, it can greatly improve the single-line production capacity and quality performance of carbon fiber, and realize low production costs, thereby breaking the application limitations brought about by the high price of carbon fiber.
Since 2019, Sinopec and CRRC have worked together to overcome the key core technologies of carbon fiber composites in the field of rail transit, and finally realized the application of carbon fiber composites on the "Bay Area Blue".
Sinopec said the next step will be to apply carbon fiber materials on the guangzhou metro line 22 trains.
In addition, the R&D teams of Sinopec and CRRC are working on carbon fiber composite material technology applied to higher performance grade models such as 400 km/h high-speed trains and maglev trains.
The material for the Beijing Winter Olympics torch "flying" is also carbon fiber from Sinopec.
This is the first time in the world that the Olympic torch shell has been made of carbon fiber composite materials, which solves the technical problem of high temperature resistance of the torch when hydrogen fuel is burned. The enclosure is capable of normal use in hydrogen-burning environments above 800 degrees Celsius.
Beijing Winter Olympics Torch. Image source: Sinopec
The torch shell of the Winter Olympics is divided into two sections: the upper section of the combustion section and the lower section of the ordinary section, and the upper and lower sections are glued to form a prefabricated part of the overall shell of the torch.
Among them, the upper section of the torch adopts carbon fiber ceramic matrix composite materials, which have excellent high temperature resistance and meet the use of the combustion environment in the upper section of the torch; the lower section adopts carbon fiber resin matrix composite materials, which have high mechanical strength and meet the overall use strength of the torch.
Jilin Chemical Fiber Group is also in the domestic leading position in the industry of large tow carbon fiber.
In July 2017, Jilin Carbon Valley Carbon Fiber Co., Ltd., a subsidiary of Jilin Chemical Fiber Group, began to study 48K large tow carbon fiber prototype on the basis of 24K raw silk experience.
In July 2018, the company developed the polymerization and spinning process technology of 48K carbon fiber filament, forming a 1,000-ton 48K carbon fiber precursor technology process package.