Viscosity Modification of High-Oleic Sunflower Oil with Polymeric Additives for the Design of New Biolubricant Formulations
L. A. QUINCHIA, M. A. DELGADO, C. VALENCIA, J. M. FRANCO,* AND C. GALLEGOS Departamento de Ingenier´ Qu´ ia imica, Facultad de Ciencias Experimentales, Universidad de Huelva, Campus Universitario de El Carmen, 21071 Huelva,Spain
Received October 29, 2008. Revised manuscript received December 17, 2008. Accepted January 26, 2009.
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 highbiodegradability, 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 sunﬂoweroil (HOSO) was blended with polymeric additives, such as ethylene vinyl acetate (EVA) and styrenebutadiene-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 °C. An Arrhenius-like equation ﬁts the evolution ofviscosity 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 viscosityincreaseswithpolymerconcentration.Speciﬁcally,EVA/ HOSO blends exhibit higher viscosity values, which are needed for applications such as lubrication of bearings and fourstroke engines. On theother hand, viscosity thermal susceptibility of HOSO samples increases with EVA or SBS concentration.
Environment concerns are rapidly gaining in importance worldwide. Among many political and social pressures on governmental departments and organizations around the world, the introduction of the ecolabeling has had signiﬁcant impact. The EU ecolabel scheme establishes criteria forgroups of products and services in order to meet high environmental and performance standards. A relatively new group of products created in this scheme is that regarding lubricants (1). Besides this, the lubricant industry in the European Community must ﬁt the REACH regulation (2) dealing with the registration, evaluation, authorization, and restriction of chemical substances.
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In general, chemical contamination of water has a remarkable negative inﬂuence on public opinion. More speciﬁcally, many coastal oil pollution cases occurring over the past few years have been reported (3, 4). For this reason, special attention is being paid to the protection of the environment against pollution exertedby lubricants and hydraulic ﬂuids based on mineral oils. It has been estimated that the fate of around 1.1 million tonnes per year (20% of the total market) of used lubricating oils in Europe is not known. In this sense, it is believed that around 600,000 tonnes of loss lubricants are released into the environment every year (5). These products include chain saw oils, concrete mold-release(“shuttering”) oils, two-stroke engine oils, chassis greases, railway wheel ﬂange greases, or lubricants for ski lifts and railway points greases (5-7). Nowadays, biodegradability has become one of the most important design parameters in both the selection of the base ﬂuid and the overall formulation of the ﬁnished lubricant (8). In this sense, the demand for biodegradable lubricants is due to a...