Melt Spinning of Cellulose Nanofibril/Polylactic Acid (CNF/PLA) Composite Fibers For High Stiffness

Nanocellulose has potential as a reinforcing agent to improve stiffness and strength in polymer fiber; however, the inherent difference in hydrophilicity makes it challenging to incorporate it into nonhydrophilic polymers, and the composite properties are strongly anisotropic. In the present work, a dual approach was employed to incorporate cellulose nanofibrils (CNFs) into polylactic acid (PLA). Polyethylene glycol (PEG) acted as a compatibilizating agent to enable the melt spinning of CNF/PLA composite fibers without water/solvent, and CNFs were surface modified to improve compatibility, increase nanoparticle thermal stability, and increase CNF dispersion in PLA. While no significant difference was observed in strength, the stiffness improved up to 600% (1.3 wt % CNF, maximum draw) in the composite fibers. This improvement was correlated with the crystallinity and fiber orientation (Hermans order parameter) for as-spun and hot-drawn fibers.