Chitral J. Angammana

Analysis of the Effects of Solution Conductivity on Electrospinning Process and Fiber Morphology

The electrospinning process and morphology of electrospun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: 1) solution properties; 2) processing conditions; and 3) ambient conditions. In this paper, we report the results of a comprehensive investigation of the effects of changing the conductivity of polyethylene oxide (PEO)/water solution on the electrospinning process and fiber morphology. The effects of the conductivity of PEO solution on the jet current and jet path are discussed. Furthermore, the fiber diameter and fiber uniformity are investigated by using scanning electron microscopy techniques.

The Effects of Electric Field on the Multijet Electrospinning Process and Fiber Morphology

Single-needle systems have been used in electrospinning experimental research; however, the low fluid throughput in fiber production has industrial limitations. To meet a high liquid-throughput requirement, several multijet schemes have recently been tested. The main drawback of these schemes is the deterioration of the local electric field at the needle tip due to the influence of other needles in the arrangement. The aim of this paper is to investigate the effects of the orientation of the needles on the electric-field distribution and, hence, on the electrospun jet characteristics and fiber morphology. Experimentally, such effects are demonstrated through the use of a polyethylene oxide solution. Further, the electric-field distribution in multineedle arrangements is simulated by using finite-element-method analysis.

Analysis of the Effects of Solution Conductivity on Electro-Spinning Process and Fiber Morphology

The electro-spinning process and morphology of electro spun nanofibers depend on many processing parameters. These parameters can be divided into three main groups: a) solution properties, b) processing conditions, c) ambient conditions. In this paper, we report the results of a comprehensive investigation of the effects of changing the conductivity of poly ethylene oxide (PEO) water solution on electro-spinning process and fiber morphology. The effects of the conductivity of PEO solution on jet current and jet path are discussed. Furthermore, fiber diameter and fiber uniformity are investigated by using scanning electron microscopy (SEM) techniques. It was found that the fiber diameter decreases with increasing solution conductivity at first, reaches a minimum value and it increases again.

Fundamentals of electrospinning and processing technologies

ABSTRACT Nanofibers have been the subject of recent intensive research due to their unique properties, especially their large surface-area-to-volume ratio, which is about 1000 times higher than that of a human hair. They also have several other remarkable characteristics, such as flexibility in surface functionality, superior mechanical properties such as stiffness and tensile strength, their capacity to be formed into a variety of shapes, and the fact that they can be produced from a wide range of organic and inorganic polymers and ceramics. These outstanding properties make polymer nanofibers the optimal candidates for providing significant improvements in current technology and for opening the door to novel applications in many research areas. The present review presents a comprehensive summary of the existing solution and melts electrospinning technologies and the effects of parameters on the electrospinning process and nanofiber morphology.

Investigation of the Optimum Electric Field for a Stable Electrospinning Process

Electrospinning is an easy and inexpensive process that produces continuous nanofibers through an electrically charged jet of polymer solution consisting of sufficiently long chain molecules. As reported in the literature, the entire electrospinning process is governed by the external electric field caused by the applied voltage between the electrodes and the induced electric field caused by free and induced charges on the fluid surface. Therefore, the electric field is the most critical parameter in electrospinning. In this work, a comprehensive analysis was carried out to investigate the effects of external and induced electric fields on the electrospinning process, which include the Taylor cone formation, the straight jet portion, and the unstable or whipping jet region. It was observed that all regions are highly influenced by the applied and induced electric fields, which results in a considerable variation in the morphology of the nanofibers.

An IGBT-Based Pulsed Power Supply for Fabricating Noncontinuous Nanofibers Using Electrospinning

Nanofibers are useful in many areas due to their outstanding characteristics, most importantly their small size and high surface-area-to-volume ratio. Recently, drug delivery systems using polymer nanofibers have gained significant attention. For these systems, a chopped nanofiber is required because the amount of drug released depends on the length of the fiber. Electrospinning is a simple method of fabricating polymer nanofibers. In the process, a high voltage is used to electrify a liquid jet which ultimately produces a solid nanofiber. The jet ejects when a high voltage is applied and vice versa. It is therefore possible to fabricate and chop nanofibers by controlling the value of the voltages applied. In this paper, an IGBT-based pulsed power supply, which can produce square pulses with a width of a few hundred microseconds and amplitudes up to 10 kV, has been designed and built. It was able to fabricate and chop nanofibers with polyethylene oxide (PEO) and a biodegradable polymer, sodium alginate blended with PEO, utilizing the aforementioned pulsed power supply. A jet always ejected during the pulse-on voltage when the duty ratio is more than 40%, with a minimum pulsewidth of approximately 80 ms.

Effects of ionic carriers on the morphological properties of electrospun nanofibres

Electrospinning is a straightforward and inexpensive process that produces continuous nanofibres from polymer solutions. The characteristics of the electrospinning process are mainly governed by the surface charge of the polymer solution which ultimately determines the fibre morphology and diameter. The charge density at the fluid surface is greatly influenced by the ionic carriers that present in the polymer solution. Therefore, in this paper, we discuss the effects of ionic carriers on the electrospinning process and hence the fibre morphology by changing the type of ions and their concentration using polyethylene oxide and polyacrylic acid solutions. The type of ions in the polymer solutions is altered by using different salts that include LiCl, NaCl, NaF, NaHCO3, KCl, and CsCl.

Experimental study of dielectric properties of fumed silica/silicone composites

Silicone rubbers are widely used polymer materials, particularly in high voltage insulation applications for their superior electrical, thermal, and chemical properties compared to other commonly used polymers. In industry, silicone elastomers are heavily filled with fumed silica particles in order to obtain superior mechanical properties. For a better understanding of the interaction between the silicon dioxide nano particles (fumed silica) and silicone rubber matrix as well as the dielectric properties of fumed silica/silicone composites, dielectric spectroscopy measurements were carried out over a wide frequency range from near DC up to 2MHz. Silicone rubber composite samples filled with surface treated fumed silica particles were prepared by hot pressing and the effects of filler concentration, filler surface treatment, and mixing method on the dielectric properties are investigated. The effect of filler-polymer interaction has been analyzed by comparing the dielectric spectroscopy measurement data with scanning electron microscopy (SEM) images.