Structure—property relationships in HDPE nanocomposites reinforced with CNF and CNF-L: mechanical strength and tribological stability

Abstract This study investigates the tribological and mechanical properties of HDPE resin, with particular emphasis on the effects of CNF and CNF-L dispersion. AFM imaging confirms that both cellulose fibers (CNF and CNF-L) consist of uniform nanofibers. EDS analysis further highlights their distinct characteristics: CNF contains potassium ions, whereas CNF-L lacks potassium but exhibits calcium ions. TGA and DTG results demonstrate that both CNF and CNF-L possess excellent thermal stability, making them suitable for processing in HDPE-based materials. The performance of HDPE composites reinforced with CNF and CNF-L was subsequently evaluated. DSC analysis revealed a slight shift in crystallization temperatures due to the presence of these nanofillers, although neither surface area nor organic modification exerted a significant influence. The crystallization temperature of the HDPE nanocomposite was approximately 1 °C higher than that of pure HDPE. XRD results indicated an increase in the crystallinity of the composite materials. Mechanical testing showed that CNF reinforcement enhanced material properties: a 2 wt.% CNF loading led to a 25.4% increase in tensile strength, a 13.6% increase in elastic modulus, and a 6.3% improvement in fracture stress. In contrast, HDPE/CNF-L nanocomposites with 1 wt.% loading exhibited a substantial reduction in the coefficient of friction (33%) and wear rate (28%). These findings suggest that the incorporation of nanofillers improves the hydrophilicity of the composites. Furthermore, the high lignin content in CNF-L may contribute to the formation of a thin lubricating film at sliding interfaces, thereby enhancing tribological performance.