The production process for PAN-based carbon fibers is as follows: polymerization of the precursor solution—spinning—preoxidation—carbonization—graphitization—surface treatment.
Specifically: Polypropylene monomers are polymerized to form the spinning solution, which is then spun into fibers. The finished raw fibers are reacted in a multi-stage oxidation furnace under an air atmosphere to produce pre-oxidized fibers; the pre-oxidized fibers are then carbonized at low and high temperatures under nitrogen protection to produce carbon fibers; after carbonization, graphitization treatment can be performed. To enhance the fibers’ bonding properties, surface treatment is required. This involves adding oxygen atoms to the fiber surface to improve chemical bonding, mildly oxidizing the surface, and etching and roughening the surface to achieve better mechanical bonding properties. Oxidation can be achieved by exposing the fibers to various gases such as air, carbon dioxide, or ozone, as well as various liquids such as sodium chlorate or nitric acid. During the later stages of surface treatment, the fibers are coated to protect them from damage during winding or weaving, a process known as sizing. Coating materials include epoxy resin, polyester, nylon, and polyurethane. After sizing, the fibers are dried to produce high-strength carbon fiber products, which can be made into carbon fiber fabrics and carbon fiber prepregs, serving as raw materials for carbon fiber composite materials. Carbon fibers are combined with resins, ceramics, and other materials to form carbon fiber composites, which are then processed through various forming processes to produce the final products required for downstream applications.