and is shot towards the grounded drum which rotates at 400 rpm before reaching the drum the solvent in the polymer solution evaporates and fibers collect on the drum the syringe pump ensures a constant flow of polymer solution and allows for the fabrication of a web with long continuous nanofibers the exact size of the fibers is affected by the flow rate of the polymer solution as well as the electrospinning voltage and the concentration of the solution due to the voltage applied to the polymer solution and the ensuing elongational flow that stretches the jet on transit to the collecting drum the polymer chains become oriented along the length of the electrospun fibers and the polymer is in a high energy state raising the temperature of the fiber mat above the characteristic glass for pvac or melting for semicrystalline polymers transition temperature of the polymer allows the chains to reconfigure to a relaxed lower energy state the result is a significant reduction in size of the fiber mat as seen in fig1 scanning electron microscopy sem was used to visualize the polymer fibers in the electrospun mats and includes views of three different mats with average fiber diameters ranging from 0 5 to 1 u03bcm referring to fig2 representative dsc traces of.