Optimizing polylactic acid composites: Role of sodium lignosulfonate-modified carbon nanotubes in mechanical and...

In this study, researchers synthesized sodium lignosulfonate (LS) modified multi-walled carbon nanotubes (L-MWCNTs) using a deep eutectic solvent (DES) method and incorporated them into polylactic acid (PLA) composite films using a solvent evaporation method. The nanofiller content ranged between 0.5 % and 1.5 % by mass. Transmission electron microscopy (TEM) confirmed the uniform dispersion of LS on the surface of MWCNTs, while scanning electron microscopy (SEM) revealed that L-MWCNTs were homogeneously distributed within PLA matrix without notable aggregation. Thermogravimetric analysis (TGA) demonstrated enhanced thermal stability, with an 8.4 % increase in residue at 800 °C. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the successful integration of L-MWCNTs into the composite films, while X-ray diffraction (XRD) analysis showed a significant increase in crystallinity (X_c) from 47.4 % to 68.9 %. With increasing L-MWCNT content, ultraviolet-visible (UV-vis) transmittance decreased from 75.9 % to 28.9 %, and oxygen (O₂) permeability was reduced by 22.4 %. At an L-MWCNT content of 1.5 %, the composite films exhibited an increase of 49.7 % and 194.5 % in tensile strength and elongation at break compared to pure PLA. These results unveil that PLA/L-MWCNT composite films possess excellent mechanical strength, thermal resistance, and barrier properties, enabling their suitability for advanced applications in packaging, medical, and electronic industries.