Viscosity Modification of High-Oleic Sunflower Oil with Polymeric Additives for the Design of New Biolubricant Formulations

Abstract

Although most common lubricants contain mineral or synthetic oils as basestocks, new environmental regulations are demanding environmentally friendly lubricants. In this sense, vegetable oils represent promising alternatives to mineral-based lubricants because of their high biodegradability, good lubricity, and low volatility. However, their poor thermooxidative stability and the small range of viscosity represent a clear disadvantage to be used as suitable biolubricants. The main objective of this work was to develop new environmentally friendly lubricant formulations with improved kinematic viscosity values and viscosity thermal susceptibility. With this aim, a high-oleic sunflower oil (HOSO) was blended with polymeric additives, such as ethylene vinyl acetate (EVA) and styrene-butadiene-styrene (SBS) copolymers, at different concentrations (0.5-5% w/w). Dynamic viscosity and density measurements were performed in a rotational rheometer and capillary densimeter, respectively, in a temperature range between 25 and 120 degrees C. An Arrhenius-like equation fits the evolution of viscosity with temperature fairly well. Both EVA and SBS copolymers may be satisfactorily used as additives to increase the viscosity of HOSO, thus improving the low viscosity values of this oil. HOSO viscosity increases with polymer concentration. Specifically, EVA/HOSO blends exhibit higher viscosity values, which are needed for applications such as lubrication of bearings and four-stroke engines. On the other hand, viscositythermal susceptibility of HOSO samples increases with EVA or SBS concentration.

Rheology of oleogels based on sorbitan and glyceryl monostearates and vegetable oils for lubricating applications

“…However, they present good lubricity and ability to adhere to metal surfaces, low volatility, small viscosity-temperature dependence and, of course, non-toxicity and high biodegradability. Some solutions for overcoming the problems related to the low viscosity of vegetable oils for different lubricating applications have also been previously reported (Quinchia et al, 2009;Garcia-Zapateiro et al, 2010). Nevertheless, the development of environmentally friendly lubricating grease formulations, based on 100% biodegradable raw materials, seems to be a much more difficult task.…”

Development of Eco-Friendly Biodegradable Biolubricant Based on Jatropha Oil

“…Ethylene-vinyl acetate (EVA) and styrene-butadiene-styrene (SBS) copolymers were used to increase the viscosity range of high-oleic sunflower oil, in order to design new environmentally friendly lubricant formulations with increased viscosities. The maximum kinematic viscosities, at 40 and 100 •C, were increased up to around 150-250 cSt and 26-36 cSt, respectively [17].…”

Response surface methodology for optimization of bio‐lubricant basestock synthesis from high free fatty acids castor oil

“…As discussed above, viscosity of acceptable range cannot be covered by conventional vegetable oils, hence in this study, structural modification was attempted to enhance the viscosity and molecular weight. However, viscosity can also be improved by addition of a viscosity enhancer [60].…”