Polyamide 66 and amino-functionalized multi-walled carbon nanotube composites and their melt-spun fibers

A series of polyamide 66 (PA66) and multi-walled carbon nanotube (MWNT) composites were condensed using amino-functionalized MWNTs (AMWNTs), hexanediamine adipate salts, and adipic acid as raw materials. The covalent grafting of maleic acid diamine onto the surfaces of the MWNTs by a Diels–Alder reaction prevented the AMWNTs from suffering entanglement, and facilitated excellent dispersion of AMWNTs in the PA66 matrix. Analyses revealed not only that the AMWNTs are uniformly dispersed in the PA66 matrix, but also that a strong interfacial interaction exists between the AMWNTs and the matrix. An AMWNT loading of only 0.5 wt% ensured a maximum dispersibility of AMWNTs in the PA66 matrix, which was far better than that of MWNTs. Additionally, the crystallization and melting behavior of PA66/AMWNT (PACNT) composite fibers were characterized. Finally, mechanical testing results demonstrated that the Young’s modulus and tensile strength of the composite fiber with 0.5 wt% AMWNT loading were increased by about 384% and 140%, respectively, compared with those of the pure PA66 fiber. Therefore, the proposed PACNT composite fibers are promising for high-performance applications.