Comparison of the thermophysical properties, microstructures, and frictional behavior of lining materials used in mine hoists

Mine hoists for medium depth and deep mines in China rely on friction hoists. Proper function of the equipment involves controlled frictional contact between a rope and a lining. While there has been a lot of empirical testing of friction hoist materials, studies of the effects of their microstructure and basic properties on friction and wear have largely been neglected. Three commercial grade linings with similar compositions were investigated (trade names: K25, G30, and GM-3). Their thermo-physical properties were measured using XPS, FTIR and TGA. Their hardness and other properties were correlated with their microstructures and frictional behavior. The DTG curves of the three linings follow a similar pattern and their weight loss rate peaks occur in the second stage due to the cyclodehydration of phenolic hydroxyl and fracture of methylene. GM-3, which is highest content of inorganic filler, had the smallest weight loss. Reciprocating sliding friction and wear tests indicated that higher contents of methylene and filler improve the friction coefficient. Adhesive wear is observed when the friction material hardness is relatively low. When the sliding velocity increases, the friction coefficient of two of the linings (K25 and GM-3) increases, but that of G30 first rises then falls. The reasons for these differences in behavior are discussed.