Tribological evaluation of selected biodegradable oils with long chain fatty acids

Abstract

Purpose - The purpose of this paper is to evaluate local biodegradable oils with long chain fatty acids namely: castor (Ricinus communis L.), jojoba (Simmondsia chinensis L.), olive (Oleo europaea L.), and sunflower (Helianthus annuus L.) oils for lubrication candidacy as a substitute to petroleum mineral oils. Design/methodology/approach - Evaluation criteria includes antiwear, lubricity, and extreme pressure (load carrying capacity) using the four-ball configuration, oxidation induction by pressure differential scanning calorimetry, thermal stability by thermo-gravimetric analyses, and viscometry using relevant American Society of Testing and Materials (ASTM) standards. Findings - The results show that the lubrication films at the interface failed by the decomposition of the metallic soaps formed by the chemical reaction of the constituent fatty acid molecules and the rubbing surfaces. The biodegradable oils show superior lubricant performance compared to the paraffin-based mineral oil, despite their poor oxidation stability. Oxidation induction and thermo-gravimetric characteristics of the biodegradable oils are closely related to their polyunsaturated and monounsaturated fatty acid composition. Originality/value - The paper shows how these biodegradable oils could be used as good substitute for petroleum mineral oils in as-received state or little antioxidant additives.