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Abstract:Polymer nanofibres are created from many different techniques, with varying rates of production. Rotary jet spinning is a relatively new technique for making nanofibres from both polymer solutions and melt. With electrospinning being by far the most widespread processing method for polymer nanofibres, we performed a direct comparison of polyamide 6 (PA6) nanofibre production between these two methods. It was found that electrospinning produced slightly smaller-diameter fibres, which scaled with a decrease in solution viscosity. In comparison, rotary jet spun fibres could be produced from a reduced range of polymer concentrations and exhibited therefore slightly larger diameters with greater variation. Crystallinity of the fibres was also compared between the two techniques and the bulk polymer, which showed a decrease in crystallinity compared to bulk PA6.

The recently popularized method of rotary jet spinning (RJS) or centrifugal spinning is investigated to evaluate the rheological limitations of polymer solutions and melts to optimal spinnability. The influence of Newtonian or non-Newtonian behavior of the polymer on spinnability is discussed. We observe that highly viscous polymers tend to block the die channels within a rotary jet spinneret and therefore suggest the use of relatively low Newtonian viscosities of between 1 and 10 Pa s for optimal fiber production. Computational fluid dynamics simulations are used in conjunction with experimental data to establish important processing parameters, such as typical shear rates in the device and optimal polymer melt or solution viscosities. A theoretical model for RJS is compared to measured fiber diameters. The comparison shows that although fiber diameters can be estimated very roughly in the case of polymer solutions, the prediction of fiber diameter in the case of polymer melts require further modeling work.

The production of high-modulus and high-strength polymer nanofibers using centrifugal or rotary jet spinning (RJS) was explored. Co-polyimide nanofibers based on 3,3 0 ,4,4 0 -biphenyltetracarboxylic dianhydride (BPDA)/p-phenylenediamine (PDA)/4,4 0 -oxydianiline (ODA) (BPO) were successfully spun by RJS from a polyamic acid precursor solution before conversion into highly oriented and chain extended BPO co-polyimide fibers via an imidization step. Fourier transform infrared (FTIR) characterization was used to evaluate the chemical conversion of the fibers. Nanocomposite laminates based on co-polyimide nonwoven fiber mats in epoxy were manufactured for mechanical testing. Analysis using the generalized rule of mixtures resulted in a back-calculated fiber modulus and strength of around 50 and 2 GPa, approaching that of high-performance fibers like Kevlar V R 29, and equaling those of co-polyimide fibers obtained via electrospinning, making them the strongest centrifugal spun fibers ever reported.GRAPHICAL ABSTRACT ARTICLE HISTORY