Wet-Spinning and Carbonization of Lignin-Polyvinyl Alcohol Precursor Fibers

Lignin is a promising bio-based precursor for sustainable carbon fibers. Limiting factors for their development include the brittleness of lignin and the lack of large-scale production routes. Here, a simple and economic wet-spinning method, suitable for the fabrication of fibers based on softwood Kraft lignin (KL) and polyvinyl alcohol (PVA), is proposed. These two polymers reveal a partial miscibility in solution, and form metastable dispersions in solid state. KL-PVA fibers are prepared at a weight ratio of 70:30 and are carbonized without thermo-stabilization. A tailor-made temperature program leads to a decreased microporosity on the fiber surfaces. The obtained carbon structures at 1000 degrees C are found to be poorly ordered, leading to only intermediate mechanical and electrical properties. However, graphitic domains appear at temperatures above 1500 degrees C and indicate a high potential for the system.