Middle-modulus high-strength polyacrylonitrile-based carbon fiber, and preparation method thereof

A middle modulus high-strength polyacrylonitrile-based carbon fiber and a preparation method of the carbon fiber belong to the technical field of fibers. The tensile strength of the fiber is 4.2GPa to 6.0GPa, and the tensile modulus is 260GPa to 310GPa. A proto-filament is prepared by wet spinning technique or dry-wet spinning technique and then subjected to pre-oxidizing and carbonizing treatments, so as to obtain the middle-modulus high-strength carbon fiber; in the polyacrylonitrile wet or dry-wet spinning process, the solvent content in the fiber is gradually controlled and the fiber is drawn effectively under the solvent condition to adjust the crystalline area and non-crystalline area orientation degree of the proto-filament, so as to obtain the polyacrylonitrile proto-filament with high orientation degree and high compactness, and finally the middle modulus high-strength polyacrylonitrile-based carbon fiber is prepared by pre-oxidization and carbonization. The fiber drawing condition is controlled by the solvent content gradual control method to gradually draw the solidified filament, so the fiber has a good orientation structure while heterogeneously solidified, and the method provided by the invention is a novel method.