Sustainable Production of Carbon Fiber: Effect of Cross-Linking in Wool Fiber on Carbon Yields and Morphologies of Derived Carbon Fiber

Currently, most of the carbon fibers are made from unsustainable fossil fuel-based precursors including high purity polyacrylonitrile (PAN) and pitch. High purity PAN is not only more expensive than wool fiber but also a limited quantity is produced because of global shortage of its monomer. In this work, various cross-linking pathways are explored as a means of altering the yield and tensile properties of carbon fiber derived from the carbonization of cross-linked wool fiber at 800 °C under nitrogen. A range of ionic and covalent-bond-forming cross-linking agents including bifunctional carboxylic acids (succinic acid and sebacic acid), a disulfonic acid (naphthalene disulfonic acid), a dialdehyde (glyoxal), and dianhydrides (succinic anhydride and itaconic anhydride) was investigated. The resulting carbon fibers were characterized in terms of chemical composition, carbon yield, surface topology, crystal structure, hydrophilicity, and tensile properties. It was found that the carbon yield can be increased by 55% by using cross-linking treatments. Carbon fiber produced from untreated and cross-linked wool fibers all exhibited superhydrophilicity. Although the tensile strength of the resulting carbon fiber was relatively low in this preliminary study, the resulting fiber could have applications in the manufacturing of thermoplastic composite materials as low modulus filler.