Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2002
Publication Date: 11/1/2002
Citation: KENAR, J.A., MCELLIGOTT, J.A., HWANG, H., ERHAN, S.Z. THERMOXIDATION KINETICS OF Z2-Z3 BLOWN SOYBEAN OIL USING DIFFERENTIAL SCANNING CALORIMETRY. JOURNAL OF THE AMERICAN OIL CHEMISTS' SOCIETY. v.79. pp.1151-1155. 2002. Interpretive Summary: The current social climate regarding environmental issues and pollution related to the use and waste disposal of non- renewable resources (petroleum based products) in industrial applications underscores the importance of utilizing renewable resources for these applications. Only through continued research to effectively utilize modified vegetable oils, will renewable resources be able to enter petroleum dominated chemical markets. Because soybean oil is readily available at low cost, it is frequently modified by blowing air through it at elevated temperatures. This modification enhances soybean oil's properties and allows it to be used industrially in the preparation of linoleum, caulking, glazing compounds, lacquers, printing inks and coatings. We have examined the thermal properties, i.e., oxidative stability and curing, of the modified soybean oil using suitable instrumentation. Our results may help researchers better understand the properties of air modified soybean oil, optimize its use in industrial materials, and expand its use into other applications. Ultimately, expanding soybean oil and its modified forms should benefit United States farmers, by increasing the demand for their soybeans and help to decrease our dependence on the ever tightening supply of non-renewable resources.
Technical Abstract: The thermoxidation of four neat blown soybean oil (BSBO) samples and a heat-bodied soybean oil sample, obtained from various manufacturers, having Gardner bubble viscosities between Z2 and Z3 were investigated using non-isothermal differential scanning calorimetry (DSC) under an oxygen flow at heating rate (beta) ranging from 3-20C/min. The observed extrapolated onset temperatures (Te1 and Te2) and temperature maximum of heat flow (Tp2) at different heating rates (beta) were determined from the DSC curves and used in conjunction with the Ozawa-Flynn-Wall (OFW) method to estimate the kinetic parameters of oil thermoxidation. At a heating rate beta = 10C/min, the calculated activation energy (Ea) for the blown soybean oil samples investigated ranged between 57.7-74.3 kJ/mol for Te1, 37.6-55.3 kJ/mol for Te2, and 54.7-63.0kJ/mol for Tp2. For comparison, a Z2- Z3 heat-bodied soybean oil sample had activation energies of 72.5, 39.8, and 61.9 for Te1, Te2, and Tp2, respectively. 1H NMR was also used to determine the amount of allylic and bis-allylic hydrogens in the blown soybean oil samples.