Research On Spinning Forming And Properties Of Bacterial Nanocellulose

With the rapid reduction of petroleum based and other non-renewable resources and environmental pollution,people are vigorously promoting bio-based green materials with excellent performance to achieve sustainable development.Bacterial nanocellulose(BC)has high aspect ratio,high crystallinity,good biocompatibility and excellent mechanical properties.It has become an important candidate material for the development of high-performance biomaterials and textiles in the future.So far,the effective transfer of nano-sized excellent mechanical properties to macrofibers is still a great challenge in the field of materials science.Various strategies have been adopted to directionally assemble nanocellulose(CNF)to obtain high strength nanocellulose-based macrofibers.However,there are still many problems in the preparation of economical and continuous high-performance macrofibers.Here,taking BC nanofibers as the basic unit,the continuous preparation from BC nanofibers to high strength macrofiber is realized through a simple and feasible preparation process.(1)The continuous preparation of BC macrofiber was realized by a combination of wet spinning and self-made grading-stretching device,and the effects of stretching rate and stretching ratio on the structure and properties of macrofiber were explored.The results show that at the optimum stretching rate of 18.85 mm/min,the macrofibers obtained by one-stage stretching at the highest stretching ratio of 40%show toughness of 18.0 MJ m-~3 and tensile strength of 544.5 MPa.On this basis,we studied the effects of two-stage stretching on the orientation and macrofiber properties of nanofibers at different stretching ratios.The results show that two-stage stretching can further improve the orientation of BC nanofibers,enhance the hydrogen bond between nanofibers and reduce defects,so as to further improve the mechanical properties of macrofibers under each stretching ratio.Under 40%stretching ratio,the toughness and tensile strength of macrofibers are as high as 17.4 MJ m-~3 and 659.8 MPa respectively.(2)In order to improve the interaction between nanofibers and improve the defects of BC macrofibers in the forming process,RSF/BC composite fiber was prepared by wet spinning process and grading-stretching.The effects of silk fibroin(RSF)on spinning,nanofiber orientation and macrofiber were investigated.The results show that the orientation of nanofibers and the mechanical properties of macrofibers can be improved by adding appropriate content of RSF.When adding 5%RSF,the toughness and tensile strength of RSF/BC composite fiber can reach24.3 MJ m-~3 and 548.4 MPa respectively.However,with the increase of RSF content,the orientation of BC nanofibers did not change significantly,but the mechanical strength decreased due to the pores and defects of the composite fibers.Under the optimum RSF ratio,the two-stage stretching was further performed on the composite fiber.When the stretching ratio was 40%,the toughness and tensile strength of the composite fiber reached 23.1 MJ m-~3 and 649.6 MPa respectively.The addition of RSF makes the assembly process of nanofibers more stable and continuous,and the macrofibers have better mechanical properties.