Green Electrospinning of Highly Concentrated Polyurethane Suspensions in Water: From the Rheology to the Fiber Morphology

Suspension electrospinning allows the environmental-friendly fabrication of nano-micro-fibrous membranes since it is based on the processing of an aqueous particle suspension in which a hydrosoluble template polymer is added to insure the formation of a continuous fiber. Here, the case of polyurethane (PU) aqueous suspensions formulated with poly(ethylene oxide) (PEO) as the template polymer is studied. The effect of several parameters (particle size, PU/PEO ratio, PEO molar mass, and PEO concentration in the continuous phase) on particle-particle and particle-template polymer interactions that influence the rheological properties of the formulation and finally the electrospinning and the fiber morphology, is studied. The goal is to process a formulation with the highest particle content as possible. Thanks to a deep rheological investigation and the study of interactions and suspension morphology by zeta potential and diffusing wave spectroscopy, it is shown that regular fibers are efficiently produced when small particles are electrospun under favorable particle-template polymer interactions and without screening the electrostatic repulsion between particles. Finally, a fibrous membrane is obtained from a formulation with a PU/PEO weight ratio equal to 50 under very stable and efficient production conditions.