Nanofibers Electrospun

A facile and low-cost method has been developed for separation of oily wastewater. Polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN) nanofibers laminated on a supporting layer were tested. In order to create highly permeable and fouling-resistant membranes, surface modifications of both fibers were conducted. The results of oily wastewater separation showed that, after low vacuum microwave plasma treatment with Argon (Ar) and chemical modification with sodium hydroxide (NaOH), the membranes had excellent hydrophilicity, due to the formation of active carboxylic groups. However, the membrane performance failed during the cleaning procedures. Titanium dioxide (TiO 2) was grafted onto the surface of membranes to give them highly permeable and fouling-resistance properties. The results of the self-cleaning experiment indicated that grafting of TiO 2 on the surface of the membranes after their pre-treatment with Ar plasma and NaOH increased the permeability and the anti-fouling properties. A new surface modification method using a combination of plasma and chemical treatment was introduced.

This paper presents a method for producing nanofibrous composite membranes for the separation of a vegetable oil–water mixture. Neat polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN) nanofibres and PVDF/PAN mixtures were used to prepare the membranes. Argon plasma treatment, followed by a chemical surface modification, was applied to alter the hydrophilicity and oleophobicity of the membranes. The obtained results showed that the membranes change their surface character (hydrophilicity and oleophilicity) in relation to the mixing ratio of the PVDF/PAN nanofibres and the surface modification parameters. These results can extend the application of PVDF, PAN and PVDF/PAN nanofibrous membranes to the treatment of oily water.

The study and development of materials at nano levels is called Nanotechnology. It is one of the enormously growing scientific field due to its huge potential in creating variety of materials that have many applications. This technology has impacted in a tremendous way in many different disciplines of science and engineering, such as electronics, tissue engineering, material science and polymer and textile engineering. Nanofibers, due to their high surface area to volume ratio, find applications as filter medium, biomedical applications,adsorption layers in protective clothing, etc. Electrospinning is a viable process to fabricate nanofibers. An in-depth study of research activities on the research and development of nanofibers, fundamental understanding of the process of electrospinning, and properties of nanomaterials and their advantages, disadvantages and applications is provided in this report. A detailed report on the type of fibers that have been electrospun, their carbonization, study of electrical conductivity and their salient features is also illustrated.
Polyacrylontirile (PAN) powder was used as a precursor to prepare the solution used in this process.Carbon nanofibers (CNFs) were derived from polyacrylonitrile (PAN) by heat treatment in an inert atmosphere. This is due to the current lack of understanding of the effect of electrospinning parameters on the quality of PAN nanofibers, as well as the effect of stabilization and carbonization temperatures on the morphology of CNFs. Post electrospinning characterization of carbon nanofibers by scanning electron microscope (SEM) concluded the best optimized parameters as: a solvent system of Polyacrylonitrile(PAN) + dimethylformamide, 5% (w/w), 15cm of spinning distance, a flow rate of 1ml/hr and an applied voltage of 12 KV for flat plate collector and 13 kV for rotating drum type collector keeping all other parameters same. With these parameters, fibers produced were smooth, continuous and the average diameter was in a range of 330to 490nm. SEM analysis showed that the rotating drum collector produced best aligned nanofibers. The range of fiber diameter produced was 270 to 420 nm.
The effect of Electrospinning parameters such as applied voltage, feed rate of polymer solution, concentration and tip to collector distance on the morphology of electrospun PAN nanofibers were studied. Fibers obtained were without any bead formation which were followed by stabilization and carbonization. The current study focusses to acquire obtaining stronger carbon fibers than those from conventional carbon fiber industry. It is aimed that the continuous carbon nanofibers from electrospun PAN are going to be the most important member of family of carbon materials.

Electrospinning is the most widely utilized method to create nanofibers because of the direct setup, the capacity to mass-deliver consistent nanofibers from different polymers, and the ability to produce ultrathin fibers with controllable diameters. Smooth and much arranged ultrafine Polyacrylonitrile (PAN) nanofibers with diameters going from submicron to nanometer were delivered utilizing Electrospinning technique. PAN powder was used as a precursor to prepare the solution utilized as a part of this process. At the point when the electrostatic repulsion contradicted surface tension, a charged stream of polymer solution was shot out from the head of the spinneret and along these lines ultrathin nonwoven fibers were created. The effect of electrospinning parameter such as applied voltage, feed rate, concentration of polymer solution and tip to collector distance on the morphology of electrospun PAN nanofibers were investigated. The nanofibers were heat treated for carbonization to examine the changes in properties and composition to make for electrical application. Scanning Electron Microscopy (SEM) was performed before and after carbonization to study electrical conductivity and morphological characterization. The SEM images have shown the uniform fiber diameter and no beads formation. The average diameter of the PAN fiber observed 365nm and 280nm for flat plat and rotating drum collector respectively. The four probe strategy was utilized to inspect the electrical conductivity of the nanofibers and the electrical conductivity is significantly improved with increase in oxidation temperature exposed.

Unidirecitonal pre-preg carbon fibers of ten peel plies were laid up at 0-, 45-, À45-, and 45-degree stacking sequences on a flat and smooth aluminum (Al) plate, and then carbonized electrospun polyacrylonitrile (PAN) nanofibers were placed on top of the last ply prior to vacuum curing in a vacuum oven. The PAN electrospun fibers were oxidized at 280 C in an ambient condition for 1 hr and then carbonized at 850 C for 1 hr in an argon (Ar) gas atmosphere. The resultant composite panels were cut into small pieces and subjected to a number of different characterization techniques. Thermal mechanical analysis (TMA) measurements clearly showed that significant reinforcement was achieved for the pre-preg/ carbonized PAN fiber composites because of the enhanced interfacial bonding between the PAN nanofibers and the matrix. Dynamic mechanical analysis (DMA) tests exhibited a shift of the glass transition temperature of the carbonized PAN nanofiber/composite, which may be helpful for high-temperature applications of the present composites. A Raman spectroscopy peak around 897 cm À1 indicated formation of the g-phase of the carbonized PAN fibers. The highest stretching peak of the CH 2 group was recognized within the range of 2,500-2,800 cm À1 for the carbonized fibers. The vibration peak of the C À À À À À À N group also appeared at 1,452 cm À1 spectrum. TMA determined the coefficient of thermal expansion (CTE), indicating an improvement in stability of the composite material, which can be useful for structural health monitoring (SHM) as well as lightning strikes and electromagnetic interference shielding applications of new carbon fiber composites.

Electrospun polyacrylonitrile (PAN) nanofibers were stabilized at 2808C for 1 h in an ambient condition, and then car-bonized at 8508C in inert argon gas for additional 1 h in order to fabricate highly pure carbonous nanofibers for the development of highly sensitive sensors in structural health monitoring (SHM) of composite aircraft and wind turbines. This study manifests the real-time strain response of the carbonized PAN nanofibers under various tensile loadings. The prepared carbon nanofibers were placed on top of the carbon fiber pre-preg composite as a single layer. Using a hand lay-up method, and then co-cured with the pre-preg composites in a vacuum oven following the curing cycle of the composite. The electric wires were connected to the top surface of the composite panels where the cohesively bonded conductive nanofibers were placed prior to the tensile and compression loadings in the grips of the tensile unit. The test results clearly showed that the carbonized electrospun PAN nanofibers on the carbon fiber composites were remarkably performed well. Even the small strain rates (e.g., 0.020% strain) on the composite panels were easily detected through voltage and resistance changes of the panels. The change in voltage can be mainly attributed to the breakage/ deformation of the conductive network of the carbonized PAN nanofibers under the loadings. The primary goal of the present study is to develop a cost-effective, lightweight, and flexible strain sensor for the SHM of composite aircraft and wind turbines. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43235.