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Thermosetting resins such as Novolac phenolic resin are commonly used as binders in the production of friction materials. It is known that the reactions between the Novolac resin and hexamethylenetetramine (used as catalyst) produce volatile compounds as ammonia. Emitted gases give rise to pores in the friction material. This forces producers to create specific pressure-no pressure cycles to avoid cracking of the material during production. The contribution of this paper deals with the reduction of volatile compounds emission during curing by modifying the composition of the mix formula using two approaches: The first one consists in adding to the formulation suitable fillers that are able to absorb volatile compounds and not to release them for temperatures up to 200°C.

Brake pad material formulation and disc microstructure/composition plays a mutual role during wear test due to the third body layer (TBL) formation and its relative evolution due to temperature change. Nevertheless these ones could influence corrosion behavior. In this study we investigated the effect of rotors characteristics on wear and sticking behavior. Rotor and brake pad microstructure were analysed with optical, metallographic and scanning electron microscope to understand the surface and TBL evolution (using different thermal preconditioning) taking into consideration also the copper role during the different wear stages. During this preliminary study we were able to find out different copper smear morphologies depending on test conditions and rotors features.

An adhesion phenomenon between brake pad and rotor frequently appears as a result of prolonged static exposure to corrosive environments. In these highly oxidative conditions, electrochemical reactions occur on the gray cast iron brake rotor surface to produce iron oxide(s), which can then penetrate the brake pad surface porosity, causing adhesion of the brake pad(s) to the rotor. In some instances the shear load necessary to detach the brake pad from the rotor is sufficiently high and becomes a real issue in the field. The corrosive mechanisms and magnitude of material interactions involved in this issue are very complex. These complexities are in part due to the heterogeneity of the rotor and friction material compositions, but also brake geometry, loading conditions, and environmental variations are large contributing factors.