A simple, one-step process for silicone modification of polyacrylonitrile fiber surfaces

Abstract

Polyacrylonitrile (PAN) fibers are used as textile fibers and precursors for carbon fiber production. In addition to bulk properties, such as high tensile strengths and good thermal and oxidative stability, surface properties of PAN fibers also play critical roles in determining their overall performance. PAN fibers are produced by wet spinning from solution and their surfaces are modified with silicone oils for both textile and carbon fiber applications. This two-step process is energy intensive and environmentally unfriendly. We developed a simple one-step process for silicone modification of PAN fiber surfaces through the addition of small amounts (0.5 to 5 wt%) of a triblock polycaprolactone-polydimethylsiloxane-polycaprolactone (PCL-PDMS-PCL) copolymer into the spinning solution, where PDMS migrated to the fiber surface during spinning and drying processes. We demonstrated that PAN fiber or film surfaces could be effectively modified with silicone with as little as 0.5 wt% PCL-PDMS-PCL additive, using this novel, one-step, energy-efficient and economical process. Influences of the average block molecular weight and the amount of silicone copolymer additive incorporated on fiber size and surface properties were investigated. As determined using scanning electron microscopy, X-ray photoelectron spectroscopy and water contact angle measurements, incorporation of PCL-PDMS-PCL produced smaller diameter, uniform, silicone-covered highly hydrophobic PAN nanofibers and films with smooth surfaces.