ARS | Publication request: Microwave Irradiation Effects on the Structure, Viscosity, Thermal Properties and Lubricity of Soybean Oil

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 14, 2006
Publication Date: January 1, 2007
Citation: Biswas, A., Adhvaryu, A., Stevenson, D.G., Sharma, B., Willett, J.L., Erhan, S.Z. 2007. Microwave irradiation effects on the structure, viscosity, thermal properties and lubricity of soybean oil. Industrial Crops and Products. 25:1-7.

Interpretive Summary: The viscosity and oxidative stability of soybean oil increased, pour point and lubricity decreased as a result of heat modification and microwave irradiation. Analysis showed no oxidation occurred for all treatments. The increase in viscosity and lowering in pour points has been explained on the basis of formation of cyclic ring structure between two triglyceride molecules. Overall microwave irradiated soybean oil shows improved oxidative stability and better low temperature stability. This microwave irradiated soybean oil has a potential to serve the dual function of antioxidant and antiwear specialty chemical in automotive and industrial applications.

Technical Abstract: Soybean oil (SBO) was heat-bodied (HB) or microwave-irradiated (MI). HB oil with Gardner bubble viscosity in the B-C range was studied as its viscosity was similar to oil MI at 200-250 deg C for 20-60 min. SBO that was HB had increased viscosity and MI further increased viscosity compared with untreated SBO. 1H NMR analysis showed no oxidiation occurred for all treatments and HB and MI oil formed a cyclic ring structure with polymerization occurring that most likely contributed to the increased viscosity. Pour point decreased from minus 9 deg C for untreated SBO to minus 15 deg C for HB and minus 18 deg C for MI, despite viscosity increasing. Pour point anomaly is likely due to triacylglyceride cyclic ring formation. Pressurized DSC analysis showed higher oxidative stability for HB oil, with even higher stability for MI oil. Compared with untreated SBO, HB and MI oil increased friction coefficient and decreased film percentage, while MI oil tended to leave larger wear scratches on ball and disk during friction measurements. MI oil improved SBO cold-flow behavior but reduced its potential as a lubricant.