Melt Spinning of Polyacrylonitrile (PAN) Fibers Based on Ionic Liquids

The production of high strength carbon fibers is an energy intensive process where a significant cost involves the wet or dry spinning of polyacrylonitrile (PAN) fiber precursors. Melt spinning PAN fibers would allow for significant reduction in production cost and production hazards. Ionic liquids (ILs) are an attractive fiber processing medium due to their negligible vapor pressure and low toxicity. In addition, they are carbon forming precursors; upon carbonization residual ILs can enhance carbon yield although primarily useful for plasticized melt spinning of PAN precursor fibers. In this presentation, the influence of the molecular structure of the ILs and the control of the plasticizing interactions with PAN during melt spinning will be discussed. The structure, thermal and mechanical properties of the melt spun PAN fibers are investigated by a combination of various characterization methods, such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and mechanical testing. Our results demonstrate that ionic liquid structure and counter-anions influence the PAN fiber formation. More specifically, ILs containing bromide counter-anions produced PAN precursor fibers with increased mechanical properties compared to ILs containing chloride anions. We believe that our research can provide foundation to understand the influence of ILs on melt spinning of PAN fibers and gives the guidelines for the more cost/energy efficient production of PAN-based carbon fibers.