Preparation Of Ultra-fine Denier Polyacrylonitrile-based Carbon Fiber Precursor

The carbon fiber is a kind of brittle material,whose tensile strength follows Griffith defect theory and Weibull weakest link theory.The main factors affecting the mechanical properties of carbon fiber are various defects of the fiber.90%of the carbon fiber defects come from genetic of precursor fiber,thereby enhancing the quality of precursor fiber is an important way to prepare excellent performance carbon fiber.According to volume effect,the smaller the fiber thickness and diameter,the fewer defects contained within the unit length,the better the mechanical properties of the carbon fiber,so the superfine of PAN precursor fiber is the effective way to improve the mechanical properties and reduce defects for carbon fiber.Through the development of new types of spinning method,changing the spinning parameters for preparing superfine PAN fiber has a very important significance for improving the performance of carbon fiber.This thesis used synthesis the PAN solution,with a set of spinning apparatus by ourselves.Spinning solution was drafted directly without the coagulation bath,and then completed to removal of the solvent and the fiber solidification.The as-spun fiber diameters were smaller than about 8?m by this method.Through changing different spinning conditions,the height of the air layer and drawing speed,SEM,XRD and strength tester were used to study the effect of as-spun fiber diameter,degree of crystalline,strength and other properties,and the increase for height of spinning the as-spun fiber diameter was found.Crystalline properties and strength have little effect,however,the increase of drawing speed can significantly reduce the fiber diameter and increase the degree of crystalline and strength.With the different drawing speed,as-spun fibers were obtained what can impact on the change of the degree of crystalline and the strength of the precursor fiber diameter by drafting in boiling water and silicone oil under 160?.We found that the smaller the diameter of the precursor fiber after drafting,the higher the crystalline of the fiber.The minimum diameter of superfine PAN precursor fiber could reach 1.4?m.