A DSC study of Z2-Z3 viscosity blown soybean oil
2002
Kenar, J.A. | McElligott, J. | Hwang, H.S. | Erhan, S.Z.
The thermal oxidation of four commercially available neat blown soybean oil samples and a heat-bodied soybean oil sample, obtained from various manufacturers, having Gardner bubble viscosities between Z(2) and Z(3) was investigated using nonisothermal DSC under a constant oxygen flow and a heating rate (β) ranging from 3 to 20°C/min. The extrapolated onset temperatures (T(e1) and T(e2)) and maximum temperature of heat flow (T(p2)) at different β were determined from the DSC curves and used in conjunction with the Ozawa-Flynn-Wall method to estimate the kinetic parameters of oil thermal oxidation. At a β of 10°C/min, the calculated activation energies (E(a)) for the blown soybean oil samples investigated ranged between 57.7 and 74.3 kJ/mol for T(e1), 37.6 and 55.3 kJ/mol for T(e2), and 54.7 and 63.0 kJ/mol for T(p2). For comparison, a Z(2)-Z(3) heat-bodied soybean oil sample had activation energies of 72.5, 39.8, and 61.9 for T(e1), T(e2), and T(p2), respectively. By (1)H NMR, the amount of allylic and bis-allylic hydrogens present in the blown soybean oil samples relative to an unmodified soybean oil sample was determined to range from 40.3 to 48.2% and 14.9 to 22.4%, respectively.
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