VEGETABLE OIL STRUCTURE AND ANTIOXIDANTS
Five vegetable oils: canola, soybean, corn, cottonseed and sunflower oils were characterized with respect to their composition by gas chromatography and viscosity. The compositions of the vegetable oils suggest that they exhibited substantially different propensity for oxidation following the order of: Canola < corn < cottonseed < sunflower ≈ soybean The effect of molecular structure of five different vegetables oils including: corn, soybean, canola, cottonseed and sunflower oils with no antioxidants added on the oxidative stability was calculated and the following order of oxidative stability would be expected: canola < corn < cottonseed < sunflower ≈ soybean. Soybean oil, which is one of the most commercially interesting of the vegetable oils in Brazil, was determined to be the most susceptible to oxidative degradation of those oils evaluated. Therefore, soybean oil was selected to be used for a study to evaluate the ability of an antioxidant to stabilize a vegetable oil relative to two commercially formulated petroleum quench oils: Micro Temp 157, a conventional oil, and Micro Temp 153B, a fast oil. The antioxidants selected for this study were Irganox L57 and Irganox L109. In addition, the potential for combinations of L57 and L109 to provide a synergistic improvement over either antioxidant individually was also examined. The results of this work showed following order of oxidative stabilization: L109 > L57 over 60 hours of accelerated testing. No synergism using a blend of L109 + L57 was observed with performance increasing with increasing amount of L109. As expected all of the antioxidant combinations evaluated were better than soybean oil with no antioxidant. However, none of the vegetable oils evaluated exhibited the oxidative stability obtained for either petroleum oil. Cooling curve analysis results were surprising since increasing viscosity observed for vegetable oils with deceasing stability did not exhibit any large effect on cooling rates or times. The reasons for this have not been definitively shown thus far.
Comparison of Oxidation Stability and Quenchant Cooling Curve Performance of Soybean Oil and Palm Oil
The potential use of vegetable oil-derived industrial oils continues to be of great interest because vegetable oils are relatively non-toxic, biodegradable, and they are a renewable basestock alternative to petroleum oil. However, the fatty ester components containing conjugated double bonds of the triglyceride structure of vegetable oils typically produce considerably poorer thermal-oxidative stability than that achievable with petroleum basestocks under typical use conditions. Typically, these conditions involve furnace loads of hot steel (850 °C), which are rapidly immersed and cooled to bath temperatures of approximately 50-60 °C. This is especially true when a vegetable oil is held in an open tank with agitation and exposed to air at elevated temperatures for extended periods of time (months or years). This paper will describe the thermal-oxidative stability and quenching performance of soybean oil and palm oil and the resulting impact on the heat transfer coefficient. These results are compared to typical fully formulated, commercially available accelerated (fast) and an unaccelerated (slow) petroleum oil-based quenchants.
Dynamic wetting angle of a spreading droplet
Abstract The dynamic contact angle is required as a boundary condition for modelling problems in capillary hydrodynamics, including certain stages of the droplet impact problem. The dynamic contact angle differs appreciably from the static advancing or receding values, even at low velocities. This paper presents experimental results of the dynamic contact angle of spreading droplets after impacting on horizontal and inclined surfaces. Droplets of an 85% (vol.) glycerin/water solution ( D  = 2.45 mm) and water ( D  = 2.7 mm) were used in the study. Two surfaces, wax (low wettable) and glass (high wettable) are used, to study the effect of surface wettability (static contact angle). The results include the dynamic contact angle of droplets together with the contact line velocity and the dimensionless spread factor as a function of time.