Mechanism And Experiment Of Preparing Nanofiber Yarn By Air-jet Spinning

Electrospun nanofibers with superfine scale, large specific surface and porosity have beenfound wider application in a wide variety of fields. Only when nanofiber yarns become suitable forbeing subjected to regular textile processes such as weaving, knitting, and embroidery would theyfind a place in the traditional textile market, which is of great commercial significance. Ifnanofibers are oriented along the yarn axis, the resultant materials will have unique optical,electrical, and mechanical properties, making them suitable for applications with added value.This paper presents a new approach for the mass production of nanofiber yarns, whichinvolves the use of a multinozzle air-jet electrospinning system and airflow twisting. In thissystem, the aggregation, orientation, and continuous bundling of nanofibers are first achievedby applying the principle of conjugate electrospinning. Three-dimensional high-speed rotatingairflow is then applied to continuously twist and spin the nanofibers into yarn. We focus on theoptimization of the apparatus parameters of air-jet electrospinning, the electric fielddistribution of multiple conjugate aggregations and the structure of nozzle. The air-jet spinningmechanism of electrospun nanofibers will be investigated based on the characterization ofnanofiber yarn structure. A new method of air-jet spinning is developed for mass production ofcontinuous electrospun nanofiber yarns. Firstly, a spinning unit air-jet electrospinningapparatus was designed. The effect of electric field distribution, air flow rate, overall solutionflow rate and applied voltage on the nanofibers productivity and nanofibers morphology wereinvestigated. It was beneficial to electrospinning at applied voltage of30kV, solution flow rateof8mL/h and air flow rate of1100mL/h. In addition, a four nozzle with straight line orrectangular arrangement air-jet electrospinning apparatus and combined16nozzle air-jet electrospinning apparatus were designed. The influences of different arrangement and distance onthe jet, the nanofibers productivity and nanofibers morphology were investigated through electricfields simulation and experiments. Research found that both the nanofibers productivity and matsarea increased at first then decreased with the increasing of nozzles distance and arrangement hadlittle effect on the nanofibers morphology, the average of nanofibers diameter was about300nm.Through the experiment of combined16nozzle air-jet electrospinning demonstrated that itsproduction which has been greater improvement was about28g/h. Therefore, multi-nozzle air-jetelectrospinning apparatus could achieve batch process of nanofibers under the suitable distance.Then the multinozzle air-jet electrospinning apparatus for bundling nanofibers was designed. Theeffect of applied voltage, air flow rate, overall solution flow rate on the diameter and production ofnanofiber bundles were analyzed. Nanofibers could be aggregated stably and bundled continuouslyat applied voltage of34kV, air flow rate of1200mL/min and overall solution flow rate of32mL/h.Finally, the airflow twisting device was designed. Numerical simulations of the airflow field withinthe nozzle were performed to understand the airflow characteristics and to study the effects ofairflow twisting on nanofiber spinning. The application of three-dimensional rotating airflowenabled continuous production of twisted nanofiber yarns with favorable orientation and uniformtwist distribution. Under an air pressure of0.4MPa, the twist angle, tensile strength, and elongationof the nanofiber yarn were73.9°,94.2MPa, and101.6%, respectively. This paper provides a newstrategy for developing nanofiber spinning method with industrial application potential.