Investigation on Oxidation Stability of Diurea Grease Using DSC

摘要

Oxidation stability (OS) of greases is one of the most important properties in the storage and use of the grease. The influences of several factors on the OS were investigated with differential scanning calorimeter (DSC), such as the structure of the diurea, the mixed grease type (soap or non-soap thickeners) and the added metal powder. Incipient oxidation temperature (IOT) served as a scale to evaluate the OS in this test. It was found that the OS of diurea was the best in all. The OS of twelve greases were determined with DSC. The diurea prepared by cycloalkyl amine has better OS than that prepared by straight chain amine when using the same diisocyanate, and the diurea grease prepared by MDI has better OS than that prepared by TDI when the amine is identical. Diurea grease was sensitive to the anti-oxidants, especially when the amount of the anti-oxidants was below 1% (wt). The IOT increased from 183.34°Cto 265.71°C or 263.38°C because of the addition of ADPA or DIOD, respectively. The OS of diurea grease was significantly improved due to the addition of some extreme pressure additives. Few influences of the antirust additives were found on the OS in the experiment. The addition of copper or nickel had negative effect on the OS. Further research is needed to clarify the mechanism.