Impact of lignocellulosic nanofiber source on the performance of polylactic acid

Composites based on polylactic acid (PLA) were developed, using lignocellulosic nanofibers (LCNF) dispersed in polyethylene glycol (PEG). To evaluate the impact of LCNF sources, suspensions were prepared from different pulps, including only cellulose; other with cellulose and hemicellulose; and cellulose, hemicellulose, and lignin. The PLA/PEG ratio was 80/20, with LCNF concentrations of 1.25%, 2.5%, and 3.75% (w/w) relative to the PLA/PEG weight. The best results were achieved with 2.5% (w/w) of LCNF containing a blend of cellulose and hemicellulose, showing a 26% increase in tensile strength and 102% in Young's modulus compared with the PLA/PEG matrix. The hemicellulose in LCNF acts as a physical barrier between cellulose chains, demonstrating a lower tendency for agglomeration and greater compatibility with PEG and PLA, as evidenced by decreased zeta potential due to the adsorption of PEG and shifts in the C=O peak in the FTIR spectra. At 3.75 LCNF concentration, micrometer-sized fibers were observed in SEM images, impacting the mechanical properties of the composites. Thermograms show no phase separation, and the change in crystallinity due to the addition of nanofibers has minimal influence on mechanical properties. These findings highlight the importance of selecting appropriate lignocellulosic nanoparticles for improved material performance.