Simultaneously electrochemical exfoliation and functionalization of graphene nanosheets: Multifunctional reinforcements in thermal, flame‐retardant, and mechanical properties of polyacrylonitrile composite fibers

Abstract Functionalized graphene has a promising prospect in improving the thermal, mechanical, and flame‐retardant properties of polymer composites, which was unfortunately limited by the low yield and high pollution during graphene production. In this study, we reported a facile and eco‐friendly electrochemical approach to prepare ferric diethylenetriaminepentakis (methylphosphonic acid) functionalized graphene nanosheets (FGNS), which were subsequently used to fabricate polyacrylonitrile (PAN) composite fibers by a wet spinning strategy. Composite fibers showed better thermal stability above 350°C in contrast to pure PAN. Furthermore, a significant improvement on flame‐retardant properties of PAN fibers in the case of peak heat release rate (decreased by 36.7%) was caused by the inclusion of FGNS. The analysis results of condensed phase revealed that FGNS facilitated the formation of the compact and graphitic char residues, protecting underlying composite fibers during combustion. With adding 3.0 wt% FGNS, the tensile strength and breaking elongation of PAN composite fibers achieved 67.6% and 126.5% increment, respectively. This electrochemical method provides an eco‐friendly approach for scale production of functional graphene.