Growing interest in sustainable bio-lubricants as alternatives to conventional mineral oils has increased the demand for renewable feedstocks that do not compete with agricultural land use. In this study, waste cooking oil (WCO) was chemically modified through transesterification/partial hydrogenation (H-FAME), partial hydrogenation (H-WCO_l and H-WCO), estolide formation (E-WCO), and epoxidation (EOs) followed by ethanol ring-opening (POs) to produce potential bio-lubricants. The thermal, physicochemical, and rheological properties of the resulting products were evaluated and compared with a commercial mineral lubricant (ISO VG 46), representative of oils used in industrial hydraulic systems. Tribological tests were performed as a preliminary comparative screening to determine friction and wear behaviour under selected pin-on-disc conditions.The WCO-derived products exhibited a broad range of properties depending on the applied chemical modification. Most samples showed thermal stability in air equal to or greater than ISO VG 46. Rheological analysis over 25-100 °C revealed Newtonian behaviour for H-FAME and POs, while E-WCO and EOs exhibited shear-thinning behaviour, indicating fluid-like and grease-like structures, respectively. Kinematic viscosity at 40 °C ranged from 3.61 to 286 cSt, with polyols (POs) displaying viscosity indices between 111 and 133, exceeding that of ISO VG 46 (107). Friction coefficients were similar across all samples, although WCO, H-WCO_l, and H-WCO showed slightly lower values. Wear testing demonstrated comparable or reduced wear for E-WCO and almost fully epoxidized oil (EO_100) relative to ISO VG 46. These results highlight the potential of WCO-derived products as sustainable bio-lubricant candidates with tuneable properties, while further tribological testing under varied load, speed, and temperature conditions will be required to assess their application-specific performance.
Rheological and tribological properties of waste cooking oil-derived bio-lubricants through multiple chemical routes
Grabovic Eugeniu;Rossi Damiano
;Anguillesi Irene;Ciulli Enrico;Seggiani Maurizia
2026-01-01
Abstract
Growing interest in sustainable bio-lubricants as alternatives to conventional mineral oils has increased the demand for renewable feedstocks that do not compete with agricultural land use. In this study, waste cooking oil (WCO) was chemically modified through transesterification/partial hydrogenation (H-FAME), partial hydrogenation (H-WCO_l and H-WCO), estolide formation (E-WCO), and epoxidation (EOs) followed by ethanol ring-opening (POs) to produce potential bio-lubricants. The thermal, physicochemical, and rheological properties of the resulting products were evaluated and compared with a commercial mineral lubricant (ISO VG 46), representative of oils used in industrial hydraulic systems. Tribological tests were performed as a preliminary comparative screening to determine friction and wear behaviour under selected pin-on-disc conditions.The WCO-derived products exhibited a broad range of properties depending on the applied chemical modification. Most samples showed thermal stability in air equal to or greater than ISO VG 46. Rheological analysis over 25-100 °C revealed Newtonian behaviour for H-FAME and POs, while E-WCO and EOs exhibited shear-thinning behaviour, indicating fluid-like and grease-like structures, respectively. Kinematic viscosity at 40 °C ranged from 3.61 to 286 cSt, with polyols (POs) displaying viscosity indices between 111 and 133, exceeding that of ISO VG 46 (107). Friction coefficients were similar across all samples, although WCO, H-WCO_l, and H-WCO showed slightly lower values. Wear testing demonstrated comparable or reduced wear for E-WCO and almost fully epoxidized oil (EO_100) relative to ISO VG 46. These results highlight the potential of WCO-derived products as sustainable bio-lubricant candidates with tuneable properties, while further tribological testing under varied load, speed, and temperature conditions will be required to assess their application-specific performance.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
