Controllable Preparation And Properties Of Carbon Nanotubes/Polyvinyl Alcohol Composite Fibers

Carbon nanotubes(CNTs)fibers have a broad application prospect for their excellent mechanical properties,electrical conductivity,thermal conductivity,knittability,lightweight,flexible,etc.Due to the high strength of individual carbon nanotubes,the preparation of macroscopic carbon nanotubes fibers with high strength has become a research focus.However,the strength of the carbon nanotubes fibers is far lower than the individual carbon nanotubes.Many structural densification methods have been used to obtain high-strength carbon nanotubes fibers,but the strength of the fibers was still limited by the weak van der Waals forces between the nanotubes.To obtain high strength carbon nanotubes fibers,it is a reliable method to use polymer binder to fill the interval between carbon nanotubes to improve the interaction between the nanotubes because the polymer molecules can increase the interaction between carbon nanotubes.Since the surface of carbon nanotubes atoms is smooth and hydrophobic,it is not conducive to polymer penetration.Therefore,the combination of surface modification and polymer penetration is very important for the preparation of high-strength fibers.In this work,we used the carbon nanotubes films prepared by chemical vapor deposition and the polyvinyl alcohol(PVA)as polymer adhesive to obtain high strength carbon nanotubes fibers.Carbon nanotubes/polyvinyl alcohol composite fibers were prepared by adding nitric acid to a polyvinyl alcohol solution in a simple way,and the presence of nitric acid promoted the better filling of polyvinyl alcohol between the carbon nanotubes.The different strengths of the composite fibers can be obtained by controlling the concentration of polyvinyl alcohol and the torsion angle of fibers.When the polyvinyl alcohol solution concentration was 1:100 and the torsion angle was 22°,the strength of the composite fibers we prepared can reach 2 GPa,which is 2.33 times stronger than the original carbon nanotubes fibers.The electrical conductivity of the composite fibers was also great,about 3.16 × 105 S/m.Due to high strength and knittability,the fibers has a broad application prospect in the fields of high-strength fibers and wearable fabric.The carbon nanotubes/ polyvinyl alcohol composite fibers were further formed into the tight structure solid structure and hollow structure helical fibers,and their performance were studied,respectively.Due to water soluble of polyvinyl alcohol,the application of tight structure composite helical fibers in actuator field was investigated.Using the mass of the copper sheet as a pull to unscrew its spiral structure and release the twist,the composite helical fibers could lift 850 times its weight and be reused.The maximum contractive strain of the helical fiber could be up to 47%.For hollow helical fibers with an aperture of 0.2 mm,the tensile strain was up to 600%,and in the process of 0%-400% of stretching,the resistance had no obvious change,which meant it has excellent stretching and electrical stability.After annealing treatment,the cycling performance of composite hollow composite fiber was improved,the residual strain of the hollow fiber was reduced to 2% under the 30% strain after annealing at 500℃ in argon for 30 minutes.