Processing and Tensile Properties of Twisted Core-Shell Yarns Fabricated by Double Nozzle Electrospinning Device

In this study, a double nozzle electrospinning device consisting of a take-up/twister unit applied to develop core-shell structured nanofibrous yarns with potential applications in the production of functional textile materials. The process was performed by introducing a pre-electrospun core yarn into the electrical field between two oppositely charged nozzles, where nanofibers cover it by a certain arrangement owning to the twisting procedure. Herein, the main goal was to investigate how the core and shell structures influenced by process parameters, can contribute to the ultimate mechanical properties of the electrospun core-shell yarn. Accordingly, the same solution of nylon 66/formic acid was used for electrospinning of both core and shell nanofibers. The response surface methodology (RSM) was applied to study the effect of twisting rate, take-up speed, and twist amount of core yarn (called pre-twist) on the morphological and tensile properties of electrospun core-shell yarns. SEM images confirmed that the nanofibers were assembled surround the core with a certain angle to the axis to form a twisted core-shell yarn. The take-up speed caused considerable effects on the yarn diameter by changing the number of fibers formed in the triangle zone of the electrospinning process. The diameter of the core-shell yarns decreased significantly by increasing the twist rate and take-up speed. Improvements in tensile stress were generally realized at low twist levels and higher take-up speeds. The contribution of the core on the mechanical behavior of core-shell yarn was also considered in detail. The electrospun core-shell yarns showed superior (∼37 %) max stress when using a core yarn with low pre-twist amounts.