Thermophysical and Tribological Properties of Highly Viscous Biolubricants

Abstract

Two new highly viscous biodegradable oils are investigated for use in wind turbine gearboxes (BIO-G00) and in mechanical transmissions of agricultural tractors (BIO-G02). Studies on their thermophysical and tribological properties were performed. High-pressure–viscosity measurements were obtained up to 250 MPa and 363.15 K using a falling-body apparatus. The viscosity of BIO-G00 and BIO-G02 reaches maximum values of 14720 and 7072 mPa·s, respectively. The film thickness and the tribological performance, from boundary to full-fluid lubrication regimes, under a slide-to-roll ratio of 5% obtained in an EHD2 ball-on-disk test rig are reported. Film thickness has also been computed through the Hamrock and Dowson equation, considering the inlet shear heating (thermal correction factor) due to the high viscosity of both biolubricants. Differences between the experimental and theoretical film thicknesses are around 4% at 353.15 K and 14% at 303.15 K for both oils. The universal pressure–viscosity coefficients, αfilm, for both oils are lower than those of other mineral and synthetic oils. Higher friction coefficients are obtained for BIO-G00 in all of the studied lubrication regimes for the different rough disks and in the entire temperature range. A suitable wetting behavior on steel surfaces is observed for both selected oils.

Controllable Synthesis and Synergistic Antioxidation Mechanism of Poly(p-methoxyphenol-phenylamine) in Biodegradable Vegetable-Based Lubricating Oils

“…22 Several lubricant properties of two new highly viscous biodegradable oils are investigated by Comunãs et al, and the results show that significant environmental benefits over the currently used mineral and synthetic oils are achieved. 23 Bernaerts et al incorporated lignin-based antioxidants in biolubricant formulations, tackling the major disadvantage of vegetable oils as environmentally friendly lubricants. 24 In more recent years, the oxidative stability of vegetable-based lubricating oils is reviewed and approaches to improve oxidative and thermal stability are described.…”

“…Around half of base oils end up in the environment due to leaks or volatilization. , The use of biodegradable base oils is an appealing alternative to traditional mineral oils, especially when they can be obtained from natural sources. − Among biobased lubricants, vegetable-based lubricating oils are mainly derived from vegetable oils such as castor oil, soybean oil, and sunflower oil. Vegetable-based lubricating oils have many advantages, such as wide sources, good renewability and biodegradation ability, and low or nontoxicity.…”

“…Girma et al synthesized lipoate ester as a multifunctional additive, which improved the antioxidant performance of high oleic sunflower oil . Several lubricant properties of two new highly viscous biodegradable oils are investigated by Comuñas et al, and the results show that significant environmental benefits over the currently used mineral and synthetic oils are achieved . Bernaerts et al incorporated lignin-based antioxidants in biolubricant formulations, tackling the major disadvantage of vegetable oils as environmentally friendly lubricants .…”