Preparation And Properties Of Modified Carbon Nanotubes/Sodium Alginate Composite Fibers

Carbon nanotubes?CNTs?have received extensive attention because of their excellent mechanical,electrical and thermal properties.Due to the extremely high surface energy of CNTs,CNTs are prone to agglomeration and difficult to disperse.Surface modification to improve their solubility,dispersibility and post-processability has become a hot spot of concern.In this paper,multi-walled carbon nanotubes?MWNTs?were covalently modified with mixed acid to prepare oxidized multi-walled carbon nanotubes?O-MWNTs?,which achieved good dispersion of MWNTs in aqueous solution and scanned.O-MWNTs were characterized and analyzed by electron microscopy and Fourier infrared spectroscopy.Sodium alginate?SA?solution and O-MWNTs were blended to prepare spinning dope with different mass ratios.SA/O-MWNTs composite fibers were prepared by different methods to test their tensile properties and water absorption.Salt absorption performance.The effects of reaction temperature,reaction time and mixed acid concentration on the weight loss rate of mixed acid oxidized MWNTs were systematically investigated.Combined with orthogonal experimental analysis,it is concluded that the concentration of mixed acid has the greatest influence on the oxidation modification of MWNTs,the reaction temperature is second,and the reaction time has the least influence.The optimum process conditions for the determination of mixed acid oxidation were as follows:mixed acid concentration 8 mol/L,reaction temperature 100?and reaction time 8 h.Infrared spectroscopy indicated that the mixed acid oxidation method successfully introduced hydrophilic reactive groups such as carboxyl group,hydroxyl group and carbonyl group on the surface of MWNTs.The SA/O-MWNTs composite fiber with different content was obtained by adjusting the ratio of O-MWNTs/SA in the spinning dope by means of syringe wet spinning.The tensile strength of the composite fiber increases first and then decreases with the addition of O-MWNTs.When the O-MWNTs/SA ratio is 25 wt%,the tensile strength of the composite fiber reaches 65MPa,and the tensile deformation reaches 13.9%.Pure SA fibers were increased by 85%and24%,respectively;SA/O-MWNTs composite fibers were prepared by a spinning process using a spinning machine.The tensile strength and tensile deformation of the composite fiber also showed a tendency to decrease first and then decrease with the addition of O-MWNTs.When the O-MWNTs/SA ratio is 1 wt%,the tensile strength of the composite fiber reaches 101MPa,and the tensile deformation reaches 19.6%,which is 57%and 17%higher than that of the pure SA fiber,respectively.After the MWNTs are modified,hydrophilic groups are introduced on the surface to enhance the hydrophilicity of the composite fibers,thereby increasing the water absorption capacity of the composite fibers.Since the composite fiber Na⁺will exchange ion with Ca²⁺,the increase of Na⁺content in the fiber will make the fiber easier to form a gel,thereby increasing its absorption capacity for physiological saline.