Looking Beyond Pure Cellulose to Lignocellulose for Regenerated Continuous Spun Filaments

The need to use naturally abundant, renewable, and sustainable precursors, such as lignin and cellulose, to produce technical textile fibers for a range of applications is rapidly growing. Being able to spin fibers directly from the biomass feedstock, without separation and purification, could significantly reduce processing costs, energy consumption, and pollution, and also retain carbon for subsequent use in carbon fiber production and other applications. Going beyond the approach of either spinning pure lignin, cellulose, or combinations of the two, continuous regenerated spun fibers have been successfully produced from dissolved and unbleached miscanthus grass pulp. The rheological and microscopic properties of the spinning dope were fully characterized as well as the structure and mechanical properties of the spun lignocellulose pulp (LCP) fibers. The highly viscous spinning dope had a zero-shear viscosity in the range 26-256 kPa·s, which resulted in spun fibers with a rough surface texture, with some undissolved lignocellulose components in the dope. The LCP fiber's orientation was determined using X-ray diffraction, displaying low- to mid-range values of <sin² θ> (0.2-0.5), which was expected at the low draw ratios used to ensure fiber consistency. Despite this, the filaments were found to have strengths in the range of 114-173 MPa, similar to wool or wet viscose rayon, and moduli of 9-12 GPa comparable to lower-range lyocell fibers. Interestingly, the micrometer-scale undissolved lignocellulose components did not inhibit the spinning process, allowing the production of what resembles continuous natural fibers. This approach shows promise for generating sustainable continuous spun fibers, without excessive pretreatment of the precursor, for technical textiles from lignocellulose pulps.