Preparation Of PIPD/SWCNT Composite Fiber And Study Of Their Structure And Properties

High-performance organic fiber has a very wide range of applications in the field of aerospace and national defense,poly [2,5-dihydroxy-1,4-phenylpyridinediimidazole](PIPD)fiber as one of them,since it was designed,it has been known for its comprehensive performance,with great development potential.However,there is still a gap between the actual and theoretical properties of PIPD fibers,such as mechanical properties,heat resistance and interfacial properties.In order to prepare PIPD fiber with better comprehensive performance,in addition to improving the polymerization and spinning process of PIPD fiber,modification of PIPD is also particularly important.In this paper,carboxylated single-wall carbon nanotubes(SWCNT)were introduced into PIPD polymer by in-situ copolymerization,and PIPD/SWCNT copolymer was prepared.PIPD/SWCNT composite fiber was prepared by dry spraywet spinning,and the composite fiber was heat treated and UV aging test.The structure of the carboxylated SWCNT was characterized by infrared spectroscopy and Raman spectroscopy,which proved that the carboxyl group was successfully introduced into the surface of SWCNT.The structure of the PIPD/SWCNT copolymer was characterized by infrared spectroscopy and Raman spectroscopy,which proved that SWCNT was successfully introduced into the PIPD molecular chain without damaging the main structure of PIPD.The molecular weight of the copolymer was characterized by viscosity method.It was found that the molecular weight of the copolymer was improved after the introduction of SWCNT,and the molecular weight of the 5 wt% PIPD/SWCNT copolymer was 32.4% higher than that of the pure PIPD polymer.The mechanical properties of PIPD/SWCNT composite fiber were characterized by universal tensile testing machine.It was found that the tensile strength of 5 wt%PIPD/SWCNT composite fiber was 26.4% higher than that of PIPD fiber.The crystallization properties of the composite fibers were characterized by X-ray diffraction,and the crystallization size decreased.Thermogravimetric tests were used to characterize the thermal properties of the composite fibers.It was found that the mass residual rate increased at 800℃.The interfacial properties of the composites were characterized by single wire pull-out test,and the interfacial shear strength of the composites increased by 18.7%.The properties of PIPD/SWCNT composite fibers after heat treatment were tested.It was found that 350℃ for 150 s was the best heat treatment condition.Under this condition,the tensile strength of the treated composite fibers increased by 22.2%compared with the primary fibers,and the crystal size and thermal decomposition temperature were significantly increased.UV aging test was carried out on PIPD/SWCNT composite fiber,and it was found that the UV resistance of the composite fiber was improved after the introduction of SWCNT.