Tribological and mechanical properties of cellulose/PMMA composite

Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) extracted from rice stalks were added to poly-methyl methacrylate (PMMA) with weight ratios of 0.1–1.0 wt%. The tribological and mechanical properties of the resulting composite materials were evaluated and compared. The addition of CNCs and CNFs reduced the wear volume by around 72–90% compared to pure PMMA samples in ball-on-disk wear tests performed against a chrome steel ball counter body. The CNC and CNF reinforcements also effectively improved flow stress under static and dynamic deformation conditions. Furthermore, the flow stress enhancement increased with an increasing CNC/CNF addition for both composite materials. For a constant strain and strain rate, the maximum enhancement effect was observed in the samples reinforced with CNFs. Overall, the CNF/PMMA showed a better tribological and mechanical performance than the CNC/PMMA. In addition, the CNFs had a longer length and higher aspect ratio than CNCs, which led to a more effective mechanical entanglement effect with the PMMA matrix. This physical entanglement improved the structural integrity of the composites. The CNC reinforcement (CNC percentage from 0% to 1.0 wt.%) also enhanced an effective improvement of about 35%∼45% in yield stress and ultimate strength under dynamic deformation conditions and static deformation conditions. Furthermore, the CNF reinforcement (CNF percentage from 0% to 1 wt%) also enhanced an effective improvement of about double yield stress and ultimate strength under dynamic deformation conditions and static deformation conditions.