Production of Modified Composite Nanofiber Yarns with Functional Particles.

The study focused on the production of modified composite nanofiber yarns with fine functional particles. A device that incorporates fine functional particles into a nanofiber yarn wrapper was specially developed, which ensures the continuous production of modified yarn. It was demonstrated during the study that the specially designed equipment could be used effectively for incorporating fine functional particles into the nanofiber packaging, thus creating a unique yarn with high application potential. The use of particles with dimensions of just tens of micrometers results in the uneven flow of particles inside the chamber and the uneven supply of particles to the composite yarn. The study also determined that the number of particles incorporated into the composite yarn is affected by the particle concentration and the variation of the vortex velocity ratios in the chamber. During testing, it was also found that the nanofiber sheet of the composite yarn improves the mechanical properties of the produced yarn. In addition, the study included the semi-industrial production of a composite filter candle, which can be used for the treatment of fluids, especially air and water.

Optimization of the Spinneret Rotation Speed and Airflow Parameters for the Nozzleless Forcespinning of a Polymer Solution.

This paper addresses the changing of the process parameters of nozzleless centrifugal spinning (forcespinning). The primary aim of this study was to determine the dependence of the final product on the dosing of the polymer, the rotation speed of the spinneret and the airflow in order to determine the extent of the technological applicability of aqueous polyvinyl alcohol (PVA) and its modifications. PVA was chosen because it is a widely used polymeric solution with environmentally friendly properties and good biodegradability. It is used in the health care and food packaging sectors. The nanofibrous layers were produced by means of a mobile handheld spinning device of our own construction. This mobile application of the spinning machine has several limitations compared to stationary laboratory equipment, mainly due to dimensional limitations. The uniqueness of our device lies in the possibility of its actual use outside the laboratory. In addition to improved mobility, another exciting feature is the combination of nozzleless forcespinning and fiber application using airflow. Dosing, the rotation speed of the spinnerets and the targeted and controlled use of air comprise the fundamental technological parameters for many devices that operate on a centrifugal force system. The rotation rate of the spinnerets primarily affects the production of fibers and their quality, while the airflow acts as a fiber transport and drying medium. The quality of the fibers was evaluated following the preparation of a testing set for the fiber layers. The most suitable combinations of rotation speed and airflow were then used in subsequent experiments to determine the ideal settings for the device. The solution was then modified by reducing the concentration to 16% and adding a surfactant, thus leading to a reduction in the diameters of the resulting fibers. The nanofiber layers so produced were examined using a scanning electron microscope (SEM) in order to analyze the number of defects and to statistically evaluate the fiber diameters.

The Potential for the Direct and Alternating Current-Driven Electrospinning of Polyamides.

The paper provides a description of the potential for the direct current- and alternating current-driven electrospinning of various linear aliphatic polyamides (PA). Sets with increasing concentrations of selected PAs were dissolved in a mixture of formic acid and dichloromethane at a weight ratio of 1:1 and spun using a bar electrode applying direct and alternating high voltage. The solubility and spinnability of the polyamides were investigated and scanning electron microscopy (SEM) images were acquired of the resulting nanofiber layers. The various defects of the spun fibers and their diameters were detected and subsequently measured. Moreover, the dynamic viscosity and conductivity were also subjected to detailed investigation. The most suitable concentrations for each of the PAs were determined according to previous findings, and the solutions were spun using a NanospiderTM device at the larger scale. The fiber diameters of these samples were also measured. Finally, the surface energy of the fiber layers produced by the NanospiderTM device was measured aimed at selecting a suitable PA for a particular application.

The Optimization of Alternating Current Electrospun PA 6 Solutions Using a Visual Analysis System.

The electrospinning process that produces fine nanofibrous materials have a major disadvantage in the area of productivity. However, alternating current (AC) electrospinning might help to solve the problem via the modification of high voltage signal. The aforementioned productivity aspect can be observed via a camera system that focuses on the jet creation area and that measures the average lifespan. The paper describes the optimization of polyamide 6 (PA 6) solutions and demonstrates the change in the behavior of the process following the addition of a minor dose of oxoacid. This addition served to convert the previously unspinnable (using AC) solution to a high-quality electrospinning solution. The visual analysis of the AC electrospinning of polymeric solutions using a high-speed camera and a programmable power source was chosen as the method for the evaluation of the quality of the process. The solutions were exposed to high voltage applying two types of AC signal, i.e., the sine wave and the step change. All the recordings presented in the paper contained two sets of data: firstly, camera recordings that showed the visual expression of electrospinning and, secondly, signal recordings that provided information on the data position in the signal function.

Fabrication of dual-functional composite yarns with a nanofibrous envelope using high throughput AC needleless and collectorless electrospinning.

Nanotechnologies allow the production of yarns containing nanofibres for use in composites, membranes and biomedical materials. Composite yarns with a conventional thread core for mechanical strength and a nanofibrous envelope for functionality, e.g. biological, catalytic, have many advantages. Until now, the production of such yarns has been technologically difficult. Here, we show an approach to composite yarn production whereby a plume of nanofibers generated by high throughput AC needleless and collectorless electrospinning is wound around a classic thread. In the resulting yarn, nanofibres can form up to 80% of its weight. Our yarn production speed was 10 m/min; testing showed this can be increased to 60 m/min. After the yarn was embedded into knitwear, scanning electron microscope images revealed an intact nanofibrous envelope of the composite yarn. Our results indicate that this production method could lead to the widespread production and use of composite nanofibrous yarns on an industrial scale.