Construction of stearamide-grafted cellulose nanocrystals as high-efficiency green lubricating additive for rapeseed...

Cellulose nanocrystals (CNCs) are being recognized as a promising green lubricating additive due to their multiple functional groups and unique structure. However, the strong hydrogen bond interactions between CNCs hinder their dispersion in base oils, significantly limiting their application in tribology. In this study, CNCs were modified with stearamide (SA) using 3-(trihydroxysilyl)-1-propanesulfonic acid (SIT) as a bridging agent to minimize the interactions among CNCs and enhance their compatibility with rapeseed oil (RSO) used as a base oil. The as-prepared CNCs/SA composite was systematically characterized by TEM, FTIR spectroscopy, and TG analysis. The results demonstrated that SA molecules were primarily attached CNCs-SIT through hydrogen bonding, and the modified CNCs/SA exhibited significantly improved dispersion stability and compatibility in RSO. This was attributed to the fact that long chains of grafted SA underwent strong interfacial interactions with the lipid molecules of RSO, resulting excellent colloidal dispersion stability and an effective reduction in the system viscosity. Furthermore, the tribological properties of CNCs/SA@RSO were investigated using a ball-on-disc friction tester. The CNCs/SA content of 0.5 wt% led to significant enhancement in the tribological performance, resulting in a 28.6% reduction in friction coefficient and 73% decrease in wear rate. This improvement was primarily attributed to the excellent dispersion stability of CNCs/SA, enabling it to function as a load-bearing and rolling agent at the sliding interface, while also creating a lubricating composite film that repaired surface roughness and micro-wear grooves. This research aims at promoting the use of CNCs as a green lubricating additive for high-value applications.