Carbon fiber industry chain - raw yarn to finished product

Carbon fiber is a kind of fiber material containing more than 95% carbon, with excellent mechanical, chemical, electrical and other excellent characteristics, is the "king of new materials", is the military and civilian development of different strategic materials, the price is very expensive, usually also known as "Black Gold".

With the continuous development of carbon fiber composite materials, it has become more and more popular among various industries, especially the strong growth of aviation, automobile, rail, wind power blades, etc. and its driving effect, the development prospect of carbon fiber industry is more promising.

The carbon fiber industry chain can be divided into upstream and downstream. Upstream usually refers to the production of carbon fiber special materials; downstream usually refers to the production of carbon fiber application parts products. The companies between the upstream and downstream can be considered as the equipment providers in the carbon fiber production process.

Upstream of the carbon fiber industry chain, the whole process from raw filament to carbon fiber needs to go through oxidation furnace, carbonization furnace, graphitization furnace, surface treatment, sizing and other processes to change the raw filament with mainly polyacrylonitrile structure into carbon fiber with mainly graphite fiber structure through carbonization and other processes.

The upstream of carbon fiber industry chain belongs to petrochemical industry, which mainly obtains acrylonitrile through crude oil refining, cracking, ammonia oxidation and other processes; carbon fiber enterprises generate acrylonitrile through polymerization of acrylonitrile-based raw materials, and then obtain raw acrylonitrile yarn through spinning, and make carbon fiber through pre-oxidation and carbonization of raw yarn, and obtain carbon fiber composites through processing of carbon fiber and high-quality resin to meet the application demand.

The production process of carbon fiber mainly includes: drawing, drafting, stabilization, carbonization and graphitization.

Drawing: This is the first step in the carbon fiber production process, mainly separating the raw material into fibers, which is a physical change, in which the mass and heat transfer between the fine flow of spinning liquid and solidification liquid, and finally PAN precipitation to form a gel structured filament strip.

Drafting: requires a temperature of 100 to 300 degrees, combined with the stretching effect of oriented fibers to operate. It is also the key step for high modulus, high reinforcement,, densification and refinement of PAN fibers.

Stabilization: Using the method of heating and oxidation at 400 degrees to convert the thermoplastic PAN linear macromolecular chain into a non-plastic heat-resistant trapezoidal structure, so that it does not melt or burn at high temperatures, maintaining the fiber morphology and thermodynamics in a stable state.

Carbonization: It is required at a temperature of 1,000 to 2,000 degrees to drive out the non-carbon elements of PAN, and finally produce carbon fibers with a disordered graphite structure containing more than 90% carbon.

Graphitization: requires a temperature of 2,000 to 3,000 degrees Celsius to transform the amorphous, disordered layer structure of the carbonized material into a three-dimensional graphite structure, which is the main technical measure to improve the modulus of carbon fiber.

The detailed process of carbon fiber from the original filament production process to the finished product is the output of the original PAN filament production process from the upper channel, after the delivery frame wet heat pre-drafting, by the drafting machine in turn to the pre-oxidation furnace, after several pre-oxidation furnace group of different gradients of temperature baking, the formation of oxidation fiber that is pre-oxygen wire; pre-oxygen wire through the medium and high temperature carbonization furnace to form carbon fiber; carbon fiber and then after the final surface treatment Sizing, drying and other processes to get the finished carbon fiber. The whole process is continuous, precise control, any slight problem in any process will affect the stable production and the quality of the final carbon fiber products. The carbon fiber production process is long, with many key technical points and high production barriers, and is an integration of multiple disciplines and technologies.