Tribological evaluation of date palm fruit syrup-a potential environmental-friendly lubricant

Date palm is one of the most cultivated palms mostly found in the Middle Eastern regions of the world. The date palm fruits are not only nutritionally rich, but also have a good amount of fatty acids such as oleic acid, palmitic acid, and linoleic acids, which have excellent anti-wear and lubricating properties, making it a potentially good candidate to be used as an environmentally-friendly lubricant. This study is a preliminary effort to explore the lubricating properties of date palm fruit syrup by conducting ball-on-disc wear tests on mild steel samples. Different concentrations (50, 75, and 100 vol %) of the syrup in water were tested at a normal load of 50 N and a sliding linear speed of 0.1 m/s. Scanning electron microscopy and optical profilometry were used to characterize the wear tracks and estimate the wear rates. 100 vol % date syrup with a viscosity of 16.95 mPa·s showed excellent results by reducing the coefficient of friction of steel-on-steel from 0.6 (dry conditions) to a value of ~0.1. The depth of the wear track reduced from ~152 μm (dry conditions) to ~11 μm, signifying a considerable reduction in wear.