Baturalp Yalcinkaya

On the nature of electric current in the electrospinning process

The electric currents between electrodes in the electrospinning process are based on the movement of charge carriers through the spinning space. Themajority of the charge carriers are formed by ionization of the air close to the metallic needle and to the polymer jet. The salt contained in the polymer solution contributes to the concentration of charge carriers, depending on its amount. The conductivity of polymer jets does not significantly affect the current since the jets do not link the electrodes.

Surface Modification of Electrospun PVDF/PAN Nanofibrous Layers by Low Vacuum Plasma Treatment

Nanofibres are very promising for water remediation due to their high porosity and small pore size. Mechanical properties of nanofibres restrict the application of pressure needed water treatments. Various PAN, PVDF, and PVDF/PAN nanofibre layers were produced, and mechanical properties were improved via a lamination process. Low vacuum plasma treatment was applied for the surfacemodification of nanofibres. Atmospheric air was used to improve hydrophilicity while sulphur hexafluoride gas was used to improve hydrophobicity of membranes. Hydrophilic membranes showed higher affinity to attach plasma particles compared to hydrophobic membranes.

Influence of salts on electrospinning of aqueous and nonaqueous polymer solutions

A roller electrospinning system was used to produce nanofibres by using different solution systems. Although the process of electrospinning has been known for over half a century, knowledge about spinning behaviour is still lacking. In this work, we investigated the effects of salt for two solution systems on spinning performance, fibre diameter, and web structure. Polyurethane (PU) and polyethylene oxide (PEO) were used as polymer, and tetraethylammonium bromide and lithium chloride were used as salt. Both polymer and salt concentrations had a noteworthy influence on the spinning performance, morphology, and diameter of the nanofibres. Results indicated that adding salt increased the spinnability of PU. Salt created complex bonding with dimethylformamide solvent and PU polymer. Salt added to PEO solution decreased the spinning performance of fibres while creating thin nanofibres, as explained by the leaky dielectric model.

Measurement and analysis of jet current and jet life in roller electrospinning of polyurethane

In this study, jet current and jet life in roller electrospinning of polyurethane (PU) were measured. The relationships between jet current and jet life and number of Taylor cones/m2 (NTC/m2), spinning performance (SP), and fiber properties (diameter, non-fibrous area) were analyzed. In addition, the effects of PU and tetraethylammonium bromide (TEAB) concentrations on jet current and jet life were determined. It was observed that jet current increases with PU and TEAB concentration, while jet life decreases. According to the results, NTC/m2 and spinning performance increase with jet current and decrease with jet life. Moreover, it was observed that jet current movement gives an idea about jet life, and it was also determined that there is a relationship between jet life and fiber morphology.

Thin Film Nanofibrous Composite Membrane for Dead-End Seawater Desalination

The aim of the study was to prepare a thin film nanofibrous composite membrane utilized for nanofiltration technologies. The composite membrane consists of a three-layer system including a nonwoven part as the supporting material, a nanofibrous scaffold as the porous surface, and an active layer. The nonwoven part and the nanofibrous scaffold were laminated together to improve the mechanical properties of the complete membrane. Active layer formations were done successfully via interfacial polymerization. A filtration test was carried out using solutions of MgSO4, NaCl, Na2SO4, CaCl2, and real seawater using the dead-end filtration method. The results indicated that the piperazine-based membrane exhibited higher rejection of divalent salt ions (>98%) with high flux. In addition, the m-phenylenediamine-based membrane exhibited higher rejection of divalent and monovalent salt ions (>98% divalent and >96% monovalent) with reasonable flux. The desalination of real seawater results showed that thin film nanofibrous composite membranes were able to retain 98% of salt ions from highly saline seawater without showing any fouling. The electrospun nanofibrous materials proved to be an alternative functional supporting material instead of the polymeric phase-inverted support layer in liquid filtration.

Analysis of the effects of rotating roller speed on a roller electrospinning system

The complexity of the free surface electrospinning process makes empirical determination of the effects of parameters very difficult. The parameters of the free surface-roller electrospinning process have not been fully defined. In this paper, new electrospinning parameters were suggested and studied. The relationship between rotating roller speed as a dependent parameter and independent parameter was investigated. The effects of rotating roller speed on electrospun nanofiber diameters and the quality of a nano web are determined experimentally. The velocity of the spinning roller and the content of salts in the solutions were selected as independent process parameters. The results show that the velocity of the rotating roller, which is related to the flow rate/feed rate of a solution on the surface of the rotating roller, affects the spinning performance as well as the quality of the fibers. Moreover, the spinnability and spinning behavior of polyurethane and polyethylene oxide solutions mainly depend on the salt content, viscosity and rotating roller speed. The high speed of the rotating roller caused a thick fiber diameter for the polyurethane solutions and polyethylene oxide, while the slow motion of the rotating roller caused low spinning performance. The diameters and diameter distribution of the electrospun nanofibers and quality of the nano web were most significantly affected by the speed of the rotating roller.

Dependent and Independent Parameters of Needleless Electrospinning

Electrospinning is a simple method to produce nanofibers from solutions and melt of different polymers and polymer blends. There is an extensive application in future of Electrospun nanofibers. Several methods for the production of nanofibers have been developed for their wide-scale production. In this chapter, we introduced the needleless roller electrospinning system that is well known under the trade name of nanospider and used as industrial production scale during the last decade. For industrial production, it is crucial to control and the measure all the spinning parameters of the needleless electrospinning system. Herein, all the electrospinning parameters of the needleless roller electrospinning system were determined and grouped as dependent and independent parameters. Each parameter was defined, and some experimental results are shown under their group. Using theoretical calculations, the minimum electrical field to start initiation of Taylor’s cone and the dimensionless electrospinning number was demonstrated. The dimensionless electrospinning number is important for the initiation of the electrospinning system. Each parameter explained in detail, and measurement methods of parameters were clarified. It was found that each parameter plays a major role in productivity and quality of nanofiber webs. Changing the dependent and independent parameters of the electrospinning, the fiber morphology can be adjusted according to demands.

Surface Modification of Composite Membranes by Coating PVA/TiO2 Layer

Water pollution comprises all of those compounds that change the quality of groundwater and surface water, therefore reducing the suitability of natural water for human use and other vital processes. These compounds result from human activities, especially those that are industrial, agricultural and domestic.The polyamide thin film composite reverse osmosis membranes become important in desalination of sea water and brackish water or waste water. However the polyamide reverse osmosis membranes tend to fouling due to their hydrophobic and rough surfaces. In this study flux and rejection of waste water from aluminum production industry were obtained during filtration process by using modified commercial composite membranes. Amount of fouling was evaluated with unmodified and modified membranes. Rejection of iron particles and PH of feed and permeate solutions were determined after filtration process. Results shows that modified membranes were performed higher metal ion rejection and antifouling performance than unmodified membranes.