Rheological and tribological properties of low-temperature greases based on cellulose acetate butyrate gel

A new approach to produce biodegradable low-temperature greases, based on cellulose acetate butyrate (CAB) that dissolves in the medium of acetyl tributyl citrate (ATBC) at high temperatures and produces a gel during cooling because of phase separation, is proposed. Rheological properties of CAB solutions and gels in a wide temperature range from −80 °C to 160 °C were investigated with characterization of their viscoelasticity and viscoplasticity that arise because of the sol-gel transition of CAB/ATBC systems at 55 °C. CAB gelation reduces the wear coefficient tenfold when using ATBC as a lubricant but leads to a noticeable increase in the friction coefficient. To improve tribological properties of gel greases, additives of various solid particles were used: hexagonal boron nitride, graphite, and polytetrafluoroethylene (PTFE). The introduction of 10% to 30% additives in a gel grease containing 10% CAB has shown the preference of PTFE at a concentration of 10% for improving grease tribological characteristics. •Cellulose acetate butyrate dissolves at high temperatures in acetyl tributyl citrate.•CAB/ATBC solution forms a gel upon cooling, becoming viscoelastic and viscoplastic.•CAB gelation greatly improves the antiwear properties of ATBC but increases friction.•Solid additives can reinforce the gel network or destroy it by creating their own net.•Polytetrafluoroethylene best improves the tribological properties of the gel grease.