Development of lubricious environmentally friendly greases using synergistic natural resources: A potential alternative to mineral oil-based greases

Abstract

The grease industry is saturated with extensive use of non-renewable, non-biodegradable, toxic, and bioaccumulative entities as ingredients that satisfy the performance goals and jeopardize the environment simultaneously. Several environmentally benign ingredients have been tried to formulate eco-friendly greases; however, a potential alternative is not yet reached. Surprisingly, the incorporation of eco-friendly additives and their synergy with the greases was least explored in this area. The present study explores, for the very first time, an effort to enhance the lubricity of eco-friendly greases (based on vegetable oil and organoclay) using biopolymers like gum acacia (GA) and guar gum (GG) as additives. Two different series of greases containing 0–10% w/w of GA and GG were developed and evaluated for a standard anti-wear (AW) test on a four-ball tester. The addition of GG in greases augments AW characteristics (≈22% improvement) and frictional response (≈42% improvement) at all concentrations. The formation of a physisorbed tribofilm at the interface is attributed to the enhanced performance. Optimal performance at 4% GG is almost equivalent to commercial grease used as the benchmark. GA-based greases, on the other hand, display inferior friction and wear characteristics. The contradictory behavior of biopolymers is attributed to their distinct interfacial interaction tendencies (synergistic or antagonistic) with organoclay.