A one-step hot pressing molding method of polyacrylonitrile carbon fibers: influence on surface morphology, microstructure and mechanical property

Carbon fibers (CFs) have been the most popular material for decades and compound into various materials because of their excellent performance. Herein, a novel one-step hot pressing molding is proposed to prepare polyacrylonitrile (PAN) CFs, eliminating the time-consuming and energy-consuming thermal stabilization stage. The fibers are tiled and pressed tightly between the two plates. The unit is then carbonized in a tubular furnace. Hot pressing enforced the fiber structure to be cyclized and reduces the damage of fibers by mitigating the escape of heteroatoms gas. The thermoplasticity of PAN fibers is innovatively utilized in the preparation of carbon fibers by hot pressing, which is able to improve density and repair the cracks. The density and tensile strength of fibers at 900 °C have reached to 1.70 g cm −3 and 1.1GPa. The CFs obtained by hot pressing molding have not only a smooth surface morphology, but also a high degree of microstructure cyclization. Hot pressing molding can not only realize the function of thermal stability stage, but also simplify the process, save energy and time, and reduce the cost.