Comparison between PDSC and oxygen bomb test methods for evaluation of grease oxidation stability

摘要

The oxidation stability is one of the key properties of a grease. The Norma-Hoffman oxygen bomb and pressure differential scanning calorimetry (PDSC) are two of the common test methods for evaluating the oxidation stability. In this paper, a comparison of the two test methods is carried out using both base and fully formulated greases. The work showed that the two methods gave good correlation when the same oxidation mechanism occurred, but not if the degradation occurred via a different mechanism or reaction order. Both methods provide information about the relative oxidation stability of greases. Comparing them, the oxygen bomb test uses a much larger quantity of grease (20g) compared to the 1 to 2mg used in the PDSC test. The oxygen bomb test allows a greater post-test analysis of the tested grease and allows the sample to be more representative of the grease being tested in oxygen bomb tests. PDSC shows a better repeatability than the oxygen bomb test. Its primary advantage is that a typical determination is completed within two hours whereas a bomb test may take up to 82 days, although typical bomb tests last only 100 hours.