Exploring biotite – a naturally occurring silicate as a sustainable additive in calcium hydroxide/castor oil eco-friendly grease for controlling friction,wear,and energy consumption

Abstract

The environmental impact of non-biodegradable lubricants has increased interest in eco-friendly alternatives. This study investigates the tribological properties of a calcium-based grease with biotite, a naturally occurring anti-wear additive, compared to molybdenum disulfide (MoS₂) which is not so environmentally friendly and commercial lithium grease. Biotite was added to calcium grease at various concentrations (0.2 wt.%, 0.4 wt.%, 0.6 wt.%, and 0.8 wt.%) along with castor oil and hydrogenated castor oil as other eco-friendly components. Thermogravimetric analysis showed that biotite-enhanced grease had superior thermal stability. Tribological testing revealed that 0.2 wt.% biotite and MoS₂ reduced wear scar diameter by 28.67% and 39.13%, and the coefficient of friction reduced by 10% and 14% as compared to the base calcium grease. The commercial lithium grease exhibited 15% and 19% higher frictional properties than our proposed calcium grease. The addition of biotite also improved the load wear index by 15.69%, demonstrating its superior anti-wear and load-carrying properties compared to MoS₂. Additionally, the biotite-enhanced grease showed 13.79% lower current consumption than commercial lithium grease. The results were also supported by the statistical analysis, which indicated higher influence of the anti-wear properties of biotite than its anti-friction properties and vice-versa in the case of molybdenum disulfide. These findings suggest that biotite can be a sustainable, cost-effective additive for improving the tribological properties of bio-based greases.