Improved boundary lubrication of perfluoropolyether using fluoropolymer-grafted cellulose nanocrystal

As the thickener for fluorine greases, polytetrafluoroethylene (PTFE) powder performs insufficient load-carrying capacity and limited assistance for friction reduction and wear resistance in the boundary lubrication regime. The present work aims to explore novel nanoparticles with higher mechanical strength as an alternative to PTFE. Cellulose nanocrystals (CNCs) were surface modified by grafting (or partially adsorbing) fluoropolymer chains and introduced into perfluoropolyether PFPE base oil. The obtained polyhexafuorobutyl methacrylate grafted CNC (CNC-g-PHFMA) powder exhibited good compatibility with the PFPE oil. The friction test and wear analysis showed that CNC-g-PHFMA formed a more intensive and stable tribo-film than PTFE on the sliding surface, resulting in more effective friction reduction (11%) and wear resistance (19%). This study demonstrates that fluoropolymer-grafted CNCs have a good application prospect in fluorine greases.