A DSC study of Z 2 −Z 3 viscosity blown soybean oil

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.