In order to keep the coefficient of friction stable, some additives such as metal sulphides, are included in the brake pads formulation. Previous work from RIMSA has shown that oxidation temperature range of the metal sulphides can be one of the key properties to explain their contribution to the performance and wear of a PAD. This new work is a step forward in the interpretation of the mechanism of sulphides as chemically active additives in the brake pads. Phenolic resin is the matrix of the brake pads and starts to decompose around 300 °C in presence of oxygen and temperature.
In order to establish a connection on between sulphide oxidation and phenolic resin degradation, several studies based on heat treatment of blends of different metal sulphides (Iron sulphide, Tin sulphide and Composite sulphide) with phenolic resin have been done. Then the material evolution was studied with techniques such as TGA-DSC, XRD, IR and SEM-EDS.
The results obtained confirm that there is an interaction between metal sulphides and resin, and the oxidation mechanism of both materials seems to be modified when they were blended. Studying PAD surface cross section after SAE J2522 and J2707, this work then introduces several SEM - EDS evidences that this mechanism can be found in the brake pads, and the results appoint that oxygen is present several tens of microns beneath the PAD surface during braking. This research will contribute to understanding the tribochemistry of the metal sulphides and phenolic resin that take place during braking and so the pad behaviour.
