Experimental and numerical study on isolated and non-isolated jet behavior through centrifuge spinning system

This work presents a comparison between an isolated and a non-isolated curved liquid jet emerging from a rotating nozzle through centrifuge spinning system. In the centrifugal spinning process, a polymer solution has been pushed by the centrifugal force through small nozzle of a rapidly rotating cylindrical drum. Thereby thin fibers are formed and collected on a collector in the form of a web. Centrifuge spinning suffered from a strong air resistance which leads to a more deflected jet as well as its rapidly solvent evaporation resulting in thicker nanofibers. In this work, centrifuge spinning has been equipped by a rotating collector, whereas the fabrication process was skillfully sealed from ambient airflow. A comparison was drawn between the trajectory of Newtonian liquid jets fabricated by centrifuge spinning and air-sealed centrifuge spinning. The captured images of the liquid jet trajectory using a high speed camera showed that non-isolated liquid jets were more curved than isolated liquid jets due to air resistance. A pre-presented non-linear analysis of the Navier-Stokes equations was carried out and the numerical solutions were compared with the experiments.There was fairly good agreement between the isolated jet trajectory and the model-predicted one, but there were differences between the non-isolated jet trajectory and the simulation results. The non-isolated jet curved more compared to the others due to air drag. Also, the diameter of polymeric nanofibers was predicted and compared with experiments. Some qualitative agreement was found

Wicking Phenomenon in Nanofiber-Coated Filament Yarns

ABSTRACT Wicking phenomenon has been investigated in filaments and spun yarns in different studies. In comparison with conventional structures, nanofibrous structures have unique characteristics such as higher surface-to-volume ratios, smaller pores, and higher porosity. For many nanofiber applications, a good understanding of the liquid absorption and wettability of nanofibrous is crucial. In this article, a modified electrospinning process for yarn coating with nanofiber is presented. In this method, fiber direction was controlled by manipulating the conventional system of electrospining and embedded nanofibers on yarn surface. Nylon66 filament was coated with nylon 66 nanofiber. The coating morphology and capillary phenomenon were examined in different concentrations of polymer solution. The kinetics of capillary flow of colored liquid in coated yarns with nanofiber follows the Lucas-Washburn equation. Results show that coating with nanofibers increases equilibrium wicking height. In a nanofiber coating process, with a constant feeding rate, increasing the solution concentration increases the capillary rise rate

Preparation of porous nanofibers from electrospun polyacrylonitrile/calcium carbonate composite nanofibers using porogen leaching technique

Production of nanofibrous polyacrylonitrile/calcium carbonate (PAN/CaCO3) nanocomposite web was carried out through solution electrospinning process. Pore generating nanoparticles were leached from the PAN matrices in hydrochloric acid bath with the purpose of producing an ultimate nanoporous structure. The possible interaction between CaCO3 nanoparticles and PAN functional groups was investigated. Atomic absorption method was used to measure the amount of extracted CaCO3 nanoparticles. Morphological observation showed nanofibers of 270–720 nm in diameter containing nanopores of 50–130 nm. Monitoring the governing parameters statistically, it was found that the amount of extraction (ε) of CaCO3was increased when the web surface area (a) was broadened according to a simple scaling law (ε = 3.18 a0.4). The leaching process was maximized in the presence of 5% v/v of acid in the extraction bath and 5 wt % of CaCO3 in the polymer solution. Collateral effects of the extraction time and temperature showed exponential growth within a favorable extremum at 50°C for 72 h. Concentration of dimethylformamide as the solvent had no significant impact on the extraction level