Modification of large tow textile grade polyacrylonitrile fiber by dopamine hydrochloride to prepare low-cost carbon fibers

Owing to high specific strength and modulus, low density, corrosion resistance, etc., polyacrylonitrile (PAN)-based carbon fibers (CFs) have been widely used in aerospace, new energy, sporting goods, and other fields. However, their application in some civil fields is limited due to their high price. Textile grade polyacrylonitrile fiber (TPF) has a structure similar to the PAN precursor of PAN-based CFs and its cost is also comparatively low, which could be expected to replace the PAN precursor in the preparation of low-cost CFs. However, the lack of active groups in the initial copolymer of TPFs leads to rapid cyclization and extremely exothermic reaction in the pre-oxidation process, which further results in the danger of fiber melting and combustion. In the present work, surface impregnation of TPFs in dopamine hydrochloride aqueous solution together with a further ultrasonic treatment were carried out, and successive pre-oxidation and carbonization resulted in the formation of TPF-based CFs. The results showed that the cyclization temperature of modified TPFs decreased significantly and the exothermic peak also widened with the introduction of oxygen anion of dopamine hydrochloride during the pre-oxidation process, and the microstructure characterization detected by FTIR, XRD and Raman confirmed that the functional groups of dopamine hydrochloric were helpful to accelerate the formation of a ladder structure. Owing to the controllable evolution of fiber architectures during the whole heat treatment process, the final tensile strength and tensile modulus of obtained TPF-based CFs were 3.31GPa and 223.80GPa, respectively.