Abstract
In the present investigation, in-situ epoxidation of waste cooking oil and its methyl esters was prepared, and the rheological behavior was analyzed for biolubricant applications. Rheological properties of the prepared epoxides were measured at a temperature of 25–100 °C, at a shear rate ranging from 5 to 300 s−1. As viscosity is one of the critical parameters for potential biolubricant applications, in the present study, the power-law model was used to investigate the flow behavior of the epoxides. The viscosity of epoxidized waste cooking oil and its methyl ester epoxides showed Newtonian flow behavior in the studied temperature range. Different shear rates (5–100, 5–300, 100–300 s−1) were studied to determine the shear rate dependency of the epoxidized waste cooking oil and its methyl ester epoxides at different temperatures. From the average viscosity values, it was shown that the epoxides show identical results at all shear rates. The dynamic viscosities of the epoxidized waste cooking oil and its methyl ester epoxides were found to be dependent on fatty acid chain length, unsaturation, and temperature. Detailed physicochemical characterization for epoxide waste cooking oil (EWCO) and epoxide waste cooking oil methyl esters (EWCOME) were carried out to evaluate the properties for suitable biolubricant applications using standard American Society for Testing and Materials (ASTM) and American Oil Chemists’ Society (AOCS) methods. Based on the viscosity for EWCO (278.9 mm2/s) and EWCOME (12.15 mm2/s) and viscosity index for EWCO (164.94) and EWCOME (151.97) of the prepared epoxides, they could complement the standard ISO vegetable grade (VG) lubricants in the market.
Highlights
In recent years, eco-friendly products such as biolubricants have played an important role over conventional products
Free fatty acid (FFA) content is always half of the Acid value (AV), which indicates the formation of soap when it is mixed with water; the estimated
An increase in viscosity is owing to the increased molecular weight, which is attributed to the addition of the oxygen molecule at the unsaturation sites, polarity, and intermolecular forces in the epoxide after reaction [29]
Summary
Eco-friendly products such as biolubricants have played an important role over conventional products. When unmodified oils are chemically modified via epoxidation, hydrogenation, esterification, and transesterification, their viscosity can be increased dramatically, making them suitable for domestic and industrial applications [12]. Epoxidized waste cooking oil and its methyl ester viscosity and viscosity index properties were compared with the standard lubricants (vegetable grade) to identify the proper area of application. To our knowledge this the first report on the rheological study of epoxide waste cooking oil (EWCO) and epoxide waste cooking oil methyl esters (EWCOME) for lubricant applications
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