Improved Tribological and Corrosion Resistance Properties of Modified Nanocelluloses as Water-Based Lubricant Additives

The development of water-based lubricant additives is trending toward higher efficiency, energy savings, multifunctionality, and biodegradability. As an eco-friendly nanomaterial, nanocellulose exhibits promising lubrication performance but can corrode steel because of its carboxyl groups. To address this, two types of nanocellulose derivatives─a nanocellulose derivative with diethanolamine grafted onto TEMPO-oxidized cellulose nanofibrils (TO-CNF-DEA) and a nanocellulose derivative with diethanolamine grafted onto cationic cellulose nanocrystals (C-CNC-DEA)─were synthesized from nanocellulose obtained through different preparation methods. The derivatives were successfully synthesized using an amide synthesis method, which involved the grafting of corrosion-resistant diethanolamine onto nanocellulose surfaces. Structural analysis indicated that the crystalline morphologies of the modified nanocellulose cellulose had smaller dimensions to a lesser extent, with their overall rodlike morphology maintained. Tribological and anticorrosion tests revealed that nanocellulose cellulose derivatives can significantly mitigate steel corrosion and reduce the friction coefficient by up to 50%. Transmission electron microscopy, energy-dispersion spectra, X-ray photoelectron spectroscopy, and Raman spectroscopy analyses demonstrate that these nanocellulose derivatives attach to metal surfaces through polar groups, forming a dense lubricating film. Additionally, smaller nanocelluloses enhanced the friction reduction performance. This not only improves the lubrication performance but also effectively shields metal surfaces from oxygen, thus improving the corrosion resistance.