The Study Of Consecutive PA6/MWNTs Nanofiber Filament By Electrospinning

Carbon nanotube (CNTs), which possesses excellent electromagnetic and mechanical properties as well as famous thermo conductive property, has attracted tremendous attention from its discovery in 1991. It has been used as a kind of reinforcement for its outstanding strength, excellent toughness and modulus of elasticity. It also can be used to prepare absorbing and shielding materials for its famous broadband absorbing character. Besides that, some researchers blended it with common fibers to produce bullet-proof vests for its high flexibility, low density, famous thermo conductive property, outstanding mechanical property, well infrared absorption and hydrophobic properties.Electrospinning is one of the most basic and convenient method to produce nanofibers, with the development of this technology, researchers began to focus on CNTs combined with electrospinning technology, try to prepare nanocomposite with excellent performance, especially when they found that CNTs can array along with the axis of the nanofiber. Presently, researchers have prepared PAN, PVA, PEO, PMMA, PA6, PBT and PLA with MWNTs or SWNTs nanofibers by electrospinning, however, most of the products by electrospinning are porous nonwovens with randomly oriented nanofiber. Prof. Frangk Ko obtained PAN/SWNTs nanofiber filaments by electrospinning, some researchers used rotate drum or double electrodes as the negative electrode obtained nanofiber filaments, whereas the length is only about several meters or even centimeters, it cannot successively rotated up like synthetic fiber spinning.In order to obtain Polymer/MWNTs nanofiber filament, we combine electrospinning method with bundling in the bath, heat setting by one-step stretch and successive rotation etc. technology, finally we successful gained consecutive PA6/MWNTs nanofiber filament. After that, we systematically discussed and optimized the parameters of the spinning process and make this method more stable and controllable.In this paper, we studied the impact mechanism of the parameters of the spinning process on the structure and properties of nanofiber filament and discovered two kinds of post-processing technology(wet post-draw and dry post-draw) to optimize the structure and properties of the filament. In the end, we discussed the microstructure and the arrangement of MWNTs in the nanofibers both with the conductivities of the filaments.The results show that when the spinning voltage was 18-20KV, the spinning distance was 6cm, the contents of MWNTs and PA6 were 0-3% and 25% respectively, the rotating speed was 1.80m/min ~12.6 m/min and use 0.5wt% peregal O aqueous solution as collection bath, the spinning process would be stable and successive.There are strong affections on the structure and properties of PA6/MWNTs nanofiber filaments by the concentrations of MWNTs, the spinning voltage, spinning distance and rotating speed. The diameters, degree of crystalline and breaking stress of the PA6/MWNTs nanofiber filaments improved according with the increase of the spinning voltage, the alignment property of the filaments and the degree of crystalline improved, the diameters of the fibers increased firstly and then decreased while the diameters of the filaments decreased, the breaking stress and initial module enhanced while the breaking strain increased firstly and the decreased according with the increase of the spinning distance. The alignment and mechanical properties of the nanofiber filament are much better in the higher spinning voltage and spinning distance when the strength of the electrical field is homology. The results also show that when the concentrations of MWNTs varied between 0.4wt%-0.8 wt%(1.57wt%-3.1wt% in the nanofiber), the increase of MWNTs content enhances the initial modules and breaking stress but reduces the breaking strain, while the breaking stress decreases when the MWNTs concentration exceeds 0.8 wt %. The initial modules and breaking stress increased as the the spinning speed raised at the range of 1.8-9.0m/min, but declined when the speed exceeded 9.0m/min.The mechanical properties of the as-spun filaments can be improved by either dry or wet post-drawing, the maximum dry and wet post-drawn ratios are 1.6 and 1.7 respectively. The mechanical property of the filament improved much more with the increase of the post-drawn ratios and the enhancement effect on the filaments by wet post-drawing is better than that dry post-drawing. The breaking stress and initial modules of the nanofiber filaments can reach 2.47 and 2.35 times respectively compared to the as-spun yarns after dry post-drawing, while 2.64 and 4.20 times increased after wet post-drawing.MWNTs can array properly in the PA6/MWNTs nanofibers but united together when the contents of it overtop its limit. The conductivity of the filaments improved according with the contents of MWNTs increased. In this study, we successfully improved the conductivity of PA6/MWNTs nanofiber filaments by 6 orders compared to the pure PA6 nanofiber filaments.The study of this paper firstly make consecutive PA6/MWNTs nanofiber filaments come true at home and abroad which break the restriction that electrospinning composite materials can only present as nonwovens with randomly oriented nanofibers, it established the theoretical and practical basis for preparing MWNTs/polymer nanofiber filaments by electrospinning. In the same time, we improved the mechanical property of the filament by dry or wet post-drawn and other post processing methods which provide a new way to enhance the mechanical property of nanocomposite fibers by electrospinning. Apart from that, We discussed the microstructure and the arrangement of MWNTs in the nanofibers both with the conductivities of the filaments, it also offered a unique technical to produce conductive nanofiber.