Modification And Properties Rearching Of PBO Fibers With GQDS

Carbon nanomaterials such as graphene,carbon nanotubes have been widely reported as fiber reinforcements.Graphene quantum dots(GQDs),as a new member of the graphene family,has rarely been reported as fiber reinforcements.The combination of GQDs and PBO fibers is expected to obtain composite fibers with superior properties.The GQDs/PBO modified fiber is then obtained by copolymerization of GQDs and PBO fibers.Firstly,carboxylated graphene quantum dots were prepared by hydrothermal reaction one-pot method.It was found that the addition of concentrated sulfuric acid in the reaction prevented the aggregation of graphene quantum dots.The size of carboxylated graphene quantum dots gradually increases with the increase of hydrothermal reaction time and decreases with the increase of concentrated sulfuric acid.The addition of concentrated sulfuric acid does not alter the structure and composition of the graphene quantum dots.The surface of the prepared carboxylated graphene quantum dots is rich in reactive functional groups.Secondly,the reaction conditions of GQDs/PBO modified fiber were investigated.As a result,it was found that the optimum temperature for terminating the reaction was 180?.During the copolymerization process,the graphene quantum dots should be ultrasonically dispersed in the polyphosphoric acid and then added to the system before the terephthalic acid chloride is added to the system.Thus,the graphene quantum dots can be more uniformly dispersed in the system.Then,we analyzed the mechanical properties,viscosity average molecular weight,crystal structure and thermodynamic properties of GQDs/PBO modified fibers with different graphene quantum dot contents.The results show that the mechanical properties and viscosity average molecular weight of GQDs/PBO modified fibers increase first and then decrease with the increase of graphene quantum dots.The mechanical properties can be increased to 15.5%,and the viscosity average molecular weight can be increased by up to 16%.The TG and DTG tests show that the initial decomposition temperature of the modified fibers relative to PBO fibers can be increased by 20?,and the final mass residual rate can be increased by 6%.