Electrospinning of viscoelastic Boger fluids: Modeling and experiments

An experimental and theoretical investigation of electrospun Newtonian and viscoelastic jets is presented. In particular, the effect of electrical conductivity and viscoelasticity on the jet profile during the initial stage of electrospinning is examined. In the theoretical study, the fluid is described as a leaky dielectric with charges only on the jet surface and viscoelastic models for polymer solutions such as Oldroyd-B and FENE-P are fully coupled with the fluid momentum equations and Gauss' law. A theoretical model for the jet is derived using a thin filament approximation, and the resulting differential equations governing electrically charged, stable polymeric jets are solved numerically. Two different experimental systems are considered: Newtonian solutions of glycerol containing trace amounts of lithium chloride salt, and viscoelastic PIB/PB Boger fluid solutions. The experimental jet profiles from electrospinning experiments are compared with the model predictions. Our results reveal that increasing the electrical conductivity of the fluid by adding salt tends to delay the jet thinning. Increasing the fluid viscoelasticity causes a more rapid initial jet thinning, however further away from the spinneret viscoelastic jets are thicker than their Newtonian counterparts due to the higher elongational viscosity. We also investigate whether the general trends observed for these fluids can be applied to predict the qualitative behavior for the spinning of other fluid systems such as PEO/water solutions that have high conductivity and viscoelasticity. (C) 2006 American Institute of Physics.