The production of a melt-spun functionalized graphene/poly(ε-caprolactam) nanocomposite fiber

An in situ polymerization technique was used to develop localized polymers grafted onto the surface of dispersed pristine graphene sheets. A 4-substituted benzoic acid monomer was grafted to the surface of expanded graphene by ‘‘Direct Friedel–Crafts” acylation. The chains of poly(ε-caprolactam) (PA6) that were grafted on the functionalized graphene (FG) were prepared by in situ polymerization of ε-caprolactam in the presence of FG. Nanocomposite fibers with different loadings of FG were melt-spun with a piston spinning machine and a hot-roller drawing machine. FG is evenly distributed in the nanocomposite. A significant mechanical property increase of FG/PA6 nanocomposite is obtained at a low FG loading; e.g., a 65% improvement of tensile strength and a 290% improvement of Young’s modulus compared to a pure PA6 fiber is achieved at a FG loading of 0.1 wt.%. The compatibility of FG and PA6 in the nanocomposite fiber improves the thermal stability of the polymer matrix. This functionalization method paves the way for the facile fabrication of graphene-based nanocomposite fibers without disrupting the primary structures of the graphene.