A high performance carbon fiber precursor containning ultra-high molecular weight acrylonitrile copolymer: preparation and properties

In order to prepare high performance carbon fiber precursor, firstly a bifunctional comonomer beta-methylhydrogen itaconate was synthesized to prepare poly (acrylonitrile-co-beta-methylhydrogen itaconate) [P (AN-co-MHI)] copolymer, which was used as carbon fiber precursor instead of poly (acrylonitrile-acrylic acid-methyl acrylate) [P (AN-AA-MA)] terpolymer; secondly a two-step method containing aqueous suspension polymerization and solution polymerization was used to prepare carbon fiber precursor. The structural evolution and stabilization mechanism of P (AN-co-MHI) and [P (AN-AA-MA)]-based carbon fiber precursor were studied by Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry, thermogravimetry; the spinnability and tensile strength were investigated by thermo scientific HAAKE CaBER1and XQ-1 tensile tester, respectively. The results show that the P (AN-co-MHI)-based carbon fiber precursor exhibits much better stabilization than that based on P (AN-AA-MA), such as lower initiation temperature, broadened heat release and smaller Ea of cyclization, which is mainly attributed to the initiation of MHI through an ionic mechanism. The carbon fiber precursor prepared by two-step method possesses better spinnability than that prepared by solution polymerization. Furthermore, the tensile strength of carbon fiber precursor prepared by two-step method has been improved by about two times, which is beneficial to preparing high performance carbon fiber.