Mechanical Properties Enhancement Of Nanofiber Bundles And One-step Preparation Of Functional Nanofiber Bundles

Nanofibers are applied in various ways due to their unique properties,and electrospinning is the efficient method to turn polymer solutions into nanofibers.Electrospun nanofibers can generally be divided into membranes and filaments.The arrangement of nanofibers in filaments is more regular than it in membranes,and performs better mechanical properties to produce 3D products.The development of functional textile manufactured with functional nanofibers has become the developing trend.However,the mechanical properties of the existing nanofiber filaments can not achieve subsequent processing needs,and lead to limit the applications of nanofiber products.Thus,this paper uses polyacrylonitrile?PAN?as the raw material to fabricate continuous PAN nanofiber filaments using multi-needle electrospinning method with countercurrent liquid bath,to aim to figure out the relationships between motion condition of bath solution and structure and properties of nanofiber filaments.The continuous forming process and mechanical properties enhancement mechanism of nanofiber filament are investigated using simulation analyze at the same time.On this basis,copper sulfates?CuSO₄?are used as deodorization finishing agent to produce deodorization nanofiber filaments,and cationic dyes are used to produce colored nanofiber filaments,and structure and properties of both filaments are investigated,respectively.The main results are as follows:A new filament constructed by continuous,uniaxial,and highly aligned nanofibers was successfully fabricated by a novel countercurrent liquid bath collection method,combined with a homemade multi-needle electrospinning device.The morphologies,crystalline structures,thermal properties,and mechanical behaviors of nanofiber filaments manufactured under different parameter combinations were investigated.The maximum breaking stress of the nanofiber filament,manufactured at a flow rate of 80 m L/min using a water inlet diameter of 6 mm,was 0.63 c N/dtex.Compared to filaments spun in a static liquid bath,the breaking stress increased by 40 %.The cyclic countercurrent liquid pumping system was started when the electrospinning process had stabilized.The forming process of electrospun nanofiber filaments using countercurrent liquid bath was divided into following stages: 1)stable polymer jet flows were formed in multiple needles;2)nanofibers were deposited on the surface of bath solution and formed into aggregation;3)the nanofiber aggregation was bundled into bundling triangular zone under stretching force;4)nanofibers transitioned to wet filaments at the first guide roller and left the surface of bath solution;5)with drying service,wet filaments were formed to day filaments.The section where the motion of bath solution enhance the mechanical properties of nanofiber filaments was the bundling triangular zone.The mechanism behind the mechanical performance enhancement of nanofiber aggregates in the bundling triangular zone was analyzed.Results showed that the fluid forces produced by the flowing liquid enhanced the uniaxial arrangement of the nanofibers and squeezed the nanofibers to smaller diameters.The motion of bath solution under the cyclic countercurrent liquid pumping system was simulated and analyzed by Fluent software,and this study focused on the velocity distribution and path line of the motion on the free surface.Results showed that bath solution did the turbulence motion,which cloud picture of velocity distribution was corresponding to the stretching process of nanofiber filament.The nanofiber aggregation was replaced by viscous liquid to proceed multiphase flow simulation.Interact was performed between bath solution and viscous liquid by changing the velocity of water inlets.The range of speed difference inside the bundling triangular zone decreased with the increasing of velocity of water inlets,which showed that the pressure,caused by bath solution motion,on the side walls of bundling triangular zone decreased.When the velocity of water inlets was too high,the whole simulation environment would be chaos.The effect caused by bath solution to the viscous liquid was quantified by orthogonal decomposition of liquid velocity in fluid velocity distribution cloud diagram in bundling triangular,the results showed that the velocity offset in the Z direction?perpendicular to the bath solution ejection direction?was larger than that in the X direction?parallel to the bath solution ejection direction?,which means the squeezing action which decreased the diameter of nanofibers played a main role in bundling process.One-step preparation technology of functional nanofiber filaments was combined by the fabricating process of nanofibers and after-treatment process.The nanofiber filaments fabricated in the bath solution contained CuSO₄ performed some blue-green color,which showed that the surface of nanofibers adsorbed a part of cupric ion.Compared with original nanofiber filaments,the breaking stress of nanofiber filaments which adsorbed cupric ion had no obvious changes,however,the strain of the functional filaments decreased obviously.The deodorized test showed that the functional filaments had deodorization effect,and the maximum deodorizes rate can reach to 32 %.Although the deodorization efficiency failed to get the expected results,the feasibility of preparation functional nanofiber filaments by one-step method was proved.On this basis,colored nanofiber filament were fabricated by adding cationic dyes into bath solution,and the results showed that the levelling property and soaping fastness of colored filaments were remarkable.