2.3.1.1 ELECTROSPINNING

During electrospinning process a high voltage (5-30 kV) is applied between a nee­dle attached to a syringe and a target. The out flowing solution gets charged which takes it to the target. During the flight the solvent evaporates and polymer fibers develop. The fibers on the target are disordered, their diameter can reach 100 nano­meter to few millimeters. The fibers can evolve thicker than the average diameter forming concentrated beads, which significantly decreases the specific surface area. The fiber diameter and the number of beads are the main characteristics of the final samples. In the electrospinning process there are given parameters which cannot be modified: humidity, temperature, pressure, atmosphere, molecular weight of the polymer. Other parameters such as viscosity, surface tension, conductivity, dielec­tric constant may be modified by selecting the appropriate polymer. The others pa­rameters may be modified directly: flow rate, voltage, diameter of the needle and the distance between the needle and the target 46.