Polyamide 66 fibers synergistically reinforced with functionalized graphene and multi-walled carbon nanotubes

Graphene and carbon nanotubes are promising strengthening additives for improving the mechanical properties of polymers. Graphene oxide (GO) and carboxylic multi-walled carbon nanotubes (CMWCNTs) were functionalized through a condensation reaction to graft melamine (M) on the GO and CMWCNTs and form products (M-gGO and M-g-CMWNTs, respectively) with amino groups. Furthermore, both M-g-GO and M-g-CMWNTs were polymerized in situ with hexanediamine adipate salts to fabricate polyamide 66(PA66)/M-g-GO/M-g-CMWNT nanocomposites. They were melt-spun into fibers with various mass ratios of M-g-GO and M-g-CMWNTs. Transmission electron microscopy confirmed that one-dimensional M-g-CMWNTs could effectively suppress the stacking of individual two-dimensional M-g-GO by bridging adjacent M-g-GO sheets, resulting in a high contact area between the M-g-GO/M-g-CMWNT structures and the polyamide 66 matrix (PA66). Scanning electron microscopy of the fracture surfaces of the composite matrix showed that the M-g-GO/M-g-CMWNT hybrid nanofillers exhibited good dispersibilities and compatibilities. Additionally, the melting and crystallization behaviors of the PA66/M-g-GO/M-g-CMWNT nanocomposite fibers were characterized. The average tensile strength of the PA66/M-g-GO/M-g-CMWNT nanocomposite fibers containing M-g-GO (0.25 wt%)/M-g-CMWNTs (0.25 wt%) was 166% higher than that of pure PA66. Moreover, the tensile strength exhibited a maximum value when the mass ratio of M-g-GO to M-g-CMWNTs was 0.25/0.25. The remarkable synergistic effect between the M-g-GO and M-g-CMWNTs for improving the mechanical properties of polyamide 66 fibers was demonstrated.

Automated summary

Graphene and carbon nanotubes were functionalized with melamine to prepare strengthening additives for polyamide 66 nanocomposites. The hybrid nanofillers of M-g-GO and M-g-CMWNT exhibited good dispersibility and compatibility, showing a synergistic effect on improving the mechanical properties of polyamide 66 fibers. The average tensile strength of the nanocomposite fibers containing M-g-GO (0.25 wt%)/M-g-CMWNTs (0.25 wt%) was 166% higher than pure PA66, with the optimal mass ratio of M-g-GO to M-g-CMWNTs being 0.25/0.25.