Electrospinning of epoxy fibers

Drawn epoxy fibers possess increasingly high mechanical properties when their diameter is decreased down to a limit of about 10 μm. Smaller diameters with even higher properties can potentially be obtained by electrospinning. Yet, electrospinning of standalone epoxy fibers has not been possible so far, because of the reactivity of epoxy and the fragility of such fibers. These difficulties are overcome in the present study by dissolving the epoxy in methyl ethyl ketone solvent, and achieving suitable electrospinning conditions by controlling the degree of epoxy crosslinking in the solution. The fibers are captured on a net screen, with the positive electrode placed behind it. The resulting electrospun fibers exhibit about 80% higher strength and stiffness compared to bulk epoxy, and striking 900% higher elongation and 1200% higher toughness. Also observed is a size-dependence of the strength on the fiber diameter, which shows a sharp strength rise to more than 300 MPa (compared to about 70 MPa in bulk epoxy) in fibers of diameters down to 3 μm. This rise in properties is likely due to anisotropic molecular rearrangement resulting from the strong stretching forces induced by electrospinning. Highly performant epoxy nanofibers could find applications in diverse fields, including reinforcement in composites, sensors, coatings and electronic devices.