OXIDATIVE PROPERTIES AND THERMAL POLYMERIZATION OF SOYBEAN OIL AND APPLICATION IN GEAR LUBRICANTS

Open Access
Author:
Arca, Mert
Graduate Program:
Chemical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 08, 2011
Committee Members:
  • Joseph Manuel Perez Sr., Thesis Advisor
Keywords:
  • thermal polymerization
  • ASTM
  • DSC
  • TGA
  • NMR
  • lubricant
  • Vegetable oil
  • diels alder
Abstract:
The use of lubricants that are based on vegetable oils is increasing rapidly due to their biodegradability, low ecotoxicity and excellent tribological properties. Biobased lubricants have lower coefficient of friction, improved wear characteristics, a higher viscosity index, and lower volatility and flashpoints than mineral based oils. Polymerized vegetable oils have found their way into many industrial applications such as inks, polymers, and hydraulic fluids. The initial objective of this thesis is to formulate a bio-based gear lubricant from thermally polymerized vegetable oils. In order to synthesize a variety of new gear oil formulations of desired properties, materials without the glycerol moiety, which is naturally in thermally modified soybean oil were desired. It was thought that Diels-Alder chemistry could be used where the thermally polymerized soybean oil could be transesterified with the desired alcohol leading to the desired thermally modified alkyl ester products. However, examinations of resultant materials showed that the cyclohexene structures expected from the type reactions are not found in these products. A new structure for thermal polymerization is suggested. Biobased gear oil was developed from soybean oil, capitalizing on the knowledge of the new structure. The soybean oil was first thermally polymerized and then mixed with additives and diluents. The effect of pour point depressants, co-base oils, anti-oxidants and anti-wear additives are reported. The final formulation of biobased gear oil gives excellent viscosimetric and wear protection properties. Lubricant testing results, including oxidation resistance are comparable to or better than commercially available gear oils. The last study of the thesis investigated oxidative degradation kinetics of vegetable base fluids. Thermal stability and deposit formation characteristics of soybean oil are studied by an isothermal thermogravimetric analyzer. Heating rate, catalysis, isothermal time, purge flow and oxygen diffusion are studied at different temperatures. Kinetic rates found from the new method are comported with the well-known Penn State Micro Oxidation test. In summary this thesis has three main objectives. The first objective is to understand the structure of thermally polymerized vegetable oils. The second one is to formulate a gear lubricant from thermally polymerized vegetable oils. The final objective of this study is to develop a method to calculate the oxidation kinetics of lubricants utilizing a readily available thermogravimetric analyzer. Soybean oil is predominantly used as a vegetable oil due to the technical properties and its worldwide availability.