Gas emission from phenolic resin composite associated with tribo-degradation

Previous studies have hypothesized that the tribo-reduction of metal oxides in phenolic resin composites is driven by the degradation of the phenolic resin. However, the temperature of the test specimens during friction tests was at most around 100 °C, which is significantly lower than the onset temperature of the degradation of phenolic resin. To elucidate the mechanism of tribo-reduction, it is essential to clarify the degradation behavior of phenolic resin under these friction conditions. In this study, we focused on the generation of gas associated with the degradation of phenolic resin and conducted in-situ measurements of the gas generated during friction using Quadrupole Mass Spectrometer (Q-MS). The results indicated an increase in ion current values corresponding to m/z values of 2, 16, 18, 28, 44, 55, 78, 91, and 95 during friction, even when the temperature of the test specimen was around 40 °C. Additionally, heating tests were conducted using Temperature-Programmed Desorption Mass Spectrometry (TPD-MS) to confirm that these m/z values were indeed caused by the degradation of the phenolic resin. At temperatures above 350 °C, the detected m/z values were similar to those observed in the friction tests. However, at temperatures below 350 °C, m/z values of 55, 78, 91, and 95 were not observed. Comparing that the degradation onset temperature of phenolic resin is around 300 °C, these results suggest that the degradation of phenolic resin takes place during the friction test, even at low temperatures of the test specimen. These findings indicate that phenolic resin degrades during friction tests, which may be the cause for tribo-reduction.