(436b) The Mechanics of Stable Electrospinning Polymer Jets and Consequences for Measurement of Polymer Extensional Viscosity
Electrospinning has gained significant attention as a method to produce polymer and composite nanofibers for a variety of emerging applications. However, realization of such applications will require simplified models for the design and control of electrospinning processes that explicitly account for the extensional rheology of electrospinning fluids. Here, we develop a simplified model based on slender body electrohydrodynamic (EHD) theory of stable jets that includes extensional strain hardening. The EHD model is analyzed during the startup of uniaxial extension, yielding predictions for the kinematics of electrospun jets solely in terms of operating conditions and independently measurable fluid properties. Experimental observations using high speed videography and velocimetry of polyethylene oxide-water jets validate scaling predictions of the model, enabling the reduction of an entire jet profile to several key parameters for comparison across different materials and operating conditions. Furthermore, the measurements allow for determination of the apparent extensional viscosity of the spinning fluid at extension rates experienced during electrospinning, which far exceed the measurable rates of conventional extensional rheometers. Finally, the theory enables correlation of electrospun fiber diameter by dimensional analysis of the EHD model that enables prediction of the electrospun fiber morphology solely from operating conditions and polymer spinning solution properties.