Thermal Oxidation Mechanism of Polyalphaolefin Greases with Lithium Soap and Diurea Thickeners: Effects of the Thickener |
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| Authors: | Lu Huang P. M. Cann George T. Y. Wan Shizhu Wen |
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| Affiliation: | 1. State Key Lab. of Tribology, Tsinghua University, Beijing, P. R. China;2. Department of Mechanical Engineering, Imperial College London, UK;3. Department of Mechanical Engineering, Imperial College London, UK |
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| Abstract: | In this work, lithium and diurea greases formulated by poly-alpha-olefin were aged up to 1,200 h in an oven at 120°C and periodically taken out for testing. Scanning electron microscopy (SEM) and infrared (IR) spectra proved that both physical and chemical degradation occurred during the thermal aging process, such as a decrease in apparent viscosity, thickener destruction, and change in chemical species. Diurea grease showed much better anti-oxidation performance during thermal aging than lithium grease. A dual effect of thermal aging on the grease lubricity was observed and analyzed. Results showed that early oxidation might reduce grease lubricity due to the formation of ketones and aldehydes, and the decrease in grease viscosity and oil bleeding due to thickener destruction would contribute to better replenishment. |
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| Keywords: | Grease thermal degradation infrared film thickness |
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