Toward continuous high-performance bacterial cellulose macrofibers by implementing grading-stretching in spinning

At present, the orderly assembly of bio-cellulose nanofibers (CNFs) with excellent mechanical properties in a simple and continuous manner still remains a challenge. Here, we propose a strategy of combining a wet spinning process with a self-made grading-stretching device to realize the continuous preparation of high-performance bacterial cellulose (BC) macrofibers. The macrofiber obtained by one-stage stretching at the optimum stretching ratio of 40% achieves the Young's modulus of 19.8 GPa and tensile strength of 544.5 MPa. Under two-stage stretching, wide-angle X-ray (WXRD) diffraction analysis revealed that the second orientation of nanofibers shows a higher degree of orientation than that under one-stage stretching. The maximum Young's modulus and tensile strength of the macrofiber can reach 33.2 GPa and 659.8 MPa, respectively, which are higher than most CNFs macrofibers obtained by spinning and post-stretching. This research is expected to provide a significant reference for the industrial spinning of nanocellulose.