Enhancing the tribological performance of hydroxypropyl methylcellulose composite coatings through nano-sized metal and oxide additives: A comparative study

Cellulose, due to its excellent mechanical and tribological properties and eco-friendliness, is suitable for environmentally friendly applications. However, its application is limited due to susceptibility to wear and damage under stress during usage. This study introduces nanosized aluminum, copper, alumina, and copper oxide into composite materials to tackle the challenges of wear and damage. This approach aims to improve the tribological performance of Hydroxypropyl methylcellulose (HPMC) composite coatings significantly. The additive particles enhanced the load-bearing capacity and wear properties of cellulose-based composite coatings. The velocity accommodation mode was provided by nano-metals through S3M2 (interaction of metal particle additives through a third-body mechanism), while for nano-oxides, it was S3M4 (expulsion of nanoparticles from the wear mark to the outer contact zone). Due to the higher specific stiffness and strength of oxides, nanofillers in the composite offered better load resistance than nano-metals, resulting in a smaller actual contact area during wear. Therefore, metal oxide nanofillers enhanced tribological properties more effectively than metal nanoparticles. Finally, detailed explanations of the tribological evidence and discussions on the mechanism were conducted.