High mechanical performance based on the alignment of cellulose nanocrystal/chitosan composite filaments through continuous coaxial wet spinning

Cellulose nanocrystals (CNCs) with high crystallinity exhibit high mechanical stiffness and strength. However, the high dispersibility of CNCs results in limited spinnability and orientation. In this study, oxidized nanocellulose was selected to obtain regionally oxidized CNCs (RO-CNC) with carboxyl groups appended. For the formation of orientable and extensible RO-CNC filaments, chitosan was introduced as the sheath solution to induce orientation by electrostatic action. The chemical structures were analyzed by Fourier transform infrared spectroscopy. The morphology of the oriented CNCs filaments was characterized by scanning electron microscopy and wide-angle X-ray scattering. Analysis of the relationship between the mechanical strength and the CNCs directional arrangement revealed that the mechanical strength of the composite fibers increased with the injection speed ratio as a result of the orientation of the RO-CNC. The mechanical strength of the oriented reinforced composite filaments reached as high as 104 MPa with an orientation index of 0.73. The tensile strength and elastic modulus of the filaments increased by 33% and 20%, respectively, compared to the unmodified CNCs spun fiber. Graphic abstract