Interaction of Nanofibrillated cellulose with lignin nanoparticles: Effects on CNF-LNP composite properties.

Lignin nanoparticles (LNP) possess unique properties that make them attractive for interaction with cellulose nanofibers (CNF). This study aimed to evaluate the effect of LNP addition on the morphological, mechanical, thermal, and chemical properties of CNF-LNP nanocomposites. Aqueous CNF suspensions with varying LNP concentrations (1 %, 5 %, and 10 % w/w) were prepared, and their rheological, structural, optical, mechanical, thermal, and spectroscopic properties were characterized. Fourier-transform infrared spectroscopy confirmed the progressive incorporation of LNP into the CNF matrix, with increased absorbance in the aromatic (∼1510 cm⁻¹) and carbonyl (∼1700 cm⁻¹) bands, reflecting significant interactions between CNF and LNP. Thermal analysis (TGA) revealed that adding 5 % LNP improved the thermal stability of CNF-LNP nanocomposites, increasing the maximum degradation temperature (Tmax) from 213.1 °C to 227.3 °C.The nanocomposite films were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), tensile tests, contact angle analysis, and spectrophotometry. An optimal 5 % LNP concentration enhanced the film properties, increasing tensile strength from 89.7 MPa to 139.7 MPa and raising the water contact angle from 24.5° to 68.3°, significantly reducing hydrophilicity. Additionally, the films demonstrated exceptional UV-blocking capabilities, achieving over 99.5 % protection against UVA and UVB radiation, highlighting potential for applications in sustainable and multifunctional materials.