Influence of metals on the phenol-formaldehyde resin degradation in friction composites

Abstract

Degradation process and influence of metal particles (Cu, Fe, CuZn) on the stability of acid catalyzed (novolak) phenolic resin during curing and friction process in friction composites have been studied. Using TGA, FTIR and Py-GC methods, the significant influence of copper and iron chips, in case of high metal concentrations, on degradation process during curing of novolac phenolic resin has been found. The same behavior was confirmed for friction process. It follows that copper and iron can act as catalysts and therefore the model mechanisms for metal catalysis were proposed. The key role in the phenolic resin degradation process belongs to the elimination of formaldehyde, as an important curing agent, caused by metal and metal oxide catalysis. Brass (CuZn) does not influence the stability regardless of concentration but the wear characteristics after friction process of brass containing samples were extremely high if compared to other ones. Brass influence is rather physical as chemical owing to formation of ZnO and consequent degradation of fiber/resin interface. This caused that CuZn particles were released from the matrix and a high porosity on the friction surface was observed.