2013 Annual Report
1a.Objectives (from AD-416):
1. Develop and apply modeling and experimental tools for the investigation and prediction of the tribological properties of farm-based raw materials.
2. Apply tribological knowledge to the development and commercialization of biobased lubricants for use in automotive and related applications.
1b.Approach (from AD-416):
(1) Review existing oxidation and cold flow literature as well as existing models for predicting oxidative stability (OS) and cold flow properties (CFP). Predictive models will be developed and used to design chemical structures that could provide improved OS and CFP without sacrificing biodegradability. Model compounds will be synthesized and evaluated using a variety of cold flow and oxidation tests such as: RBOT, PDSC, PP, CP, cryogenic DSC. Models will be further modified as needed and applied in development of new bio-based raw materials and promising structures will be synthesized in large quantities for bench- and pilot-scale evaluations. Tribological and tribochemical properties of model bio-based structures will be investigated and used in model development. Structures to be investigated include: polarity, unsaturation, branching, chain length, cyclic rings (mono- and poly-cyclic aromatic and aliphatic structures), and various combinations of structures. Model structures will be evaluated for boundary, hydrodynamic, mixed, EHD, traction, and tribochemical properties. (2) Develop database on lubricating and hydraulic fluids to set-up target specifications and also to develop predictive structure-property relationships. Various grades of lubricating and hydraulic fluids will be developed using variety of in-house tests such as: RBOT, PDSC, PP, CP, EHL film thickness, TC, foaming, corrosion, volatility, viscosity, viscosity-index, pressure-viscosity coefficient, friction and wear (AW and EP), biodegradability, etc. Promising formulations will be further developed using appropriate bench tests. Examples of bench tests used in lubricating oil development include: Thin Film Oxygen Uptake Test; Cold Cranking Simulator; Mini-Rotary Viscometer; gas emission tests; Thermo-Oxidation Engine Oil Simulation Test; Corrosion Bench Test; Distillation; Piston cleanliness; etc. Bench tests to be used in biobased hydraulic fluid development include: vane pump; corrosion; foam; oxidation; water separability; thermal stability; hydrolytic stability; and sludge formation. Promising biobased formulations will be further subjected to qualification tests and long-term evaluations for specific applications. Starch modified by steam-jet cooking or chemical modification will be used to develop starch-based metalworking lubricants. The effect of various structural and formulation variables on performance will be investigated, including starch chemical structure; type and degree of chemical modification; oil chemical structure; oil-to-starch ratio; lubricant additives chemistry and concentration. Tests to be used in these evaluations include: friction and wear; product quality; tool life; productivity; lubricant batch life; ease of lubricant handling; compatibility with machine components; etc. The results will be used to select formulations for further development on small- and pilot-scale equipment.
ARS scientists in the Bio-Oils Research Unit at the USDA-ARS National Center for Agricultural Utilization Research, Peoria, Illinois, are using a multi-faceted approach involving chemical synthesis, tribological characterization, and structure-property modeling to develop biobased lubricants with properties and costs comparable to petroleum based lubricants currently on the market. Also, the scientists are exploring new applications for new molecules synthesized under this program. During FY13, progress has been made in all these areas.
Full tribological investigations were conducted on a variety of biobased oils developed in this project and in several other collaborating projects. Except for the new crop oils, which were investigated without further chemical modifications, most biobased oils investigated have been subjected to some sort of chemical or enzymatic modifications. These structural modifications can be divided into three categories: (1) elimination of reactive double bonds via conversion into ester or other side chains (e.g., acetates); (2) insertion of functional groups with potential anti-wear or extreme pressure properties (e.g., sulfur containing groups); and (3) a combination of (1) and (2). These modifications are intended to produce biobased oils with improved tribological properties, including improvements in some or all of the following properties: oxidation stability, cold flow properties, anti-wear, and extreme pressure. In addition to the biobased oils, commercial petroleum based products were selected and subjected to full tribological characterization for comparison purposes.
The data from the full tribological characterization of the biobased oils and the corresponding commercial petroleum based products were carefully analyzed to determine why some biobased structures performed as well as the commercial products while others displayed poor performance. The results of the analysis were used to develop structure-property correlations which were used to propose potential biobased structures with beneficial tribological properties. This approach was used to propose new biobased phosphonate and biobased lipoyl derivatives predicted to have superior performance. These new structures will be synthesized, characterized, and the results used to enhance the predictive quality of the structure-property models.
Thioether-functionalized vegetable oils, developed under this program, were investigated for potential application in the remediation of metal-contaminated water. In this investigation, thioether-functionalized corn and canola oils were used to treat water containing about 600 ppm of silver ions. After ~100 min, the canola-functionalized oil removed more than half of the silver ions, reducing its concentration to below 300 ppm. The corn-functionalized oil was more effective, removing the silver ion to below its detection limit in the water. These results are very promising and further research is underway. Heavy metal contamination of water sources is a major concern worldwide and the use of biobased remediation will result in a new market for farm products. Exploration of alternate applications will continue.
Biobased fluids with extreme pressure properties from vegetable oils. Extreme pressure additives are used in a wide range of lubricant formulations that operate under extreme conditions (high temperature, high pressure, high shear, reactive metal surface, etc.), such as those encountered by metalworking fluids, gear oils, and hydraulic oils. Extreme pressure additives undergo tribochemical reactions under the lubrication condition and generate in situ tribofilms that reduce friction and wear, and prevent damage to friction elements. Extreme pressure additives currently on the market are all petroleum based and have environmental and health issues. ARS scientists in the Bio-Oils Research Unit, in collaboration with ARS scientists in the Renewable Product Technology Research Unit, both at the USDA-ARS National Center for Agricultural Utilization Research (NCAUR), Peoria, Illinois, enzymatically modified high oleic vegetable oil to provide it with extreme pressure properties and evaluated its performance relative to a commercial petroleum based extreme pressure additive. Analysis of the results indicated competitive performance between the biobased and the commercial petroleum-based extreme pressure product. More work is needed to bring cost parity between the biobased and commercial products. A biobased and environmentally friendly extreme pressure additive with comparable performance and costs similar to petroleum based extreme pressure products will be an attractive alternative for major formulators and suppliers of metalworking fluids and other lubricants.
Biobased phosphonate derivatives with comparable anti-wear (AW) properties to commercial AW additives. Vegetable oils have a number of lubrication properties that make them preferable over petroleum based oils, including excellent biodegradability, viscosity, viscosity index, and volatility. However, for certain high demanding applications (e.g., engine oils, hydraulic oils, metalworking fluids), the use of vegetable oils requires formulation with performance enhancing additives such as AW additives. Unfortunately, widely used commercial AW additives such as zinc dialkyl dithiophosphate (ZDDP) contain heavy metals and other elements that may pose undesirable environmental and health risks. ARS scientists in the Bio-Oils Research Unit at the USDA-ARS National Center for Agricultural Utilization Research (NCAUR), Peoria, Illinois, synthesized a number of biobased phosphorus-containing AW additives and compared their performance to ZDDP. The evaluation showed that certain structures of biobased phosphonate derivatives display AW performance close to that of ZDDP. Successful replacement of ZDDP with biobased AW additives will: (1) open a vast new market for agricultural products and (2) have a beneficial impact on the environment.
Biresaw, G., Bantchev, G.B. 2013. Pressure viscosity coefficient of vegetable oils. Tribology Letters. 49(3):501-512.
Bantchev, G.B., Biresaw, G. 2013. Elastohydrodynamics of farm-based blends comprising amphiphilic oils. In: Biresaw, G., Mittal, K.L., editors. Surfactants in Tribology. Volume 3. Boca Raton, FL: CRC Press. p. 265-298.
Bantchev, G.B., Biresaw, G., Vermillion, K., Appell, M.D. 2013. Synthesis and spectral characterization of methyl 9(10)-dialkylphosphonostearates. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 110:81-91.
Bantchev, G.B., Biresaw, G. 2012. Film-forming properties of blends of high-oleic sunflower oil with polyalkyl glycol. Journal of the American Oil Chemists' Society. 89:2227-2235.
Biresaw, G., Bantchev, G.B. 2013. Tribological properties of biobased ester phosphonates. Journal of the American Oil Chemists' Society. 90(6):891-902.
Dunlap, C.A., Biresaw, G., Shearer, J.F. 2012. Captive bubble and sessile drop surface characterization of a submerged aquatic plant, Hydrilla verticillata. Current Topics in Phytochemistry. 11:53-58.
Sutivisedsak, N., Leathers, T.D., Nunnally, M.S., Price, N.P., Biresaw, G. 2013. Utilization of agricultural biomass in the production of the biopolymer schizophyllan. Journal of Indusrial Microbiology and Biotechnology. 40(1):105-112. DOI: 10.1007/s10295-012-1208-8.