Melt electrospinning: Electrodynamics and spinnability

Abstract

The electrodynamics of the polymer melt as well as its effects on fiber spinnability in the framework of laser-heated melt electrospinning was investigated. We challenge the classic views in the aspects of the molten Taylor-cone, the thinning process, and the jet deformation. A temperature-voltage phase diagram was constructed to distinguish the regimes of the bending, the whipping, and the break-up of the jet. These jet kinematics are significantly dependent on the molten Taylor-cone, the jet thinning, and the forces exerted on the jet. The surface tension restricts the growth of the jet while it can be safely neglected after jet initiation. Jet breaks up periodically at the tip of Taylor-cone if the polymer viscosity is too low or the elongation rate is not high enough to stretch the jet. The elongation rate for each segment of the jet keeps almost constant at a certain melt temperature, while the elongation rate increases and the solidification point of the jet shifts from the Taylor-cone to the target with increasing melt temperature. An analytic equation is proposed to estimate the jet diameter along the spinline before jet solidifies. Additionally, the experiment of coiling proved that the electrical and the elastic as the dominant forces for bending are gradually replaced by the inertial and the viscous forces for whipping.