Effect of phenolic content on tribological behavior of carbonized copper-phenolic based friction material

The purpose of the present study is to investigate the effect of phenolic content on mechanical and tribological properties of a series of semi-carbonized copper/phenolic resin-based semi-metallic friction materials with resin contents ranging from 30 to 70 vol% (5-25 wt%). Experimental results indicate that all materials reduced in thickness and weight after semi-carbonization treatment. The amounts of the reductions increased with phenolic content. The sample comprising 50 vol% resin (R5) exhibited the maximum compressive strength, hardness and increase in density after semi-carbonization. Among all materials, R5 demonstrated the greatest potential with high and stable coefficient of friction (COF) value (0.3-0.4) and reasonably low wear. The materials containing 60 vol% (R6) and 70 vol% (R7) phenolic resin showed relatively low COF values. The sample containing 40 vol% resin (R4) faded quickly, while the sample containing 30 vol% phenolic resin (R3) failed prematurely during testing. Semi-carbonization treatment itself did not cause significant oxidation, but friction-induced heating caused extensive oxidation to surfaces of the materials. More counter-face material was transferred to the surfaces of samples with higher phenolic contents (R4, R5, R6 and R7) during sliding, while more extensive abrasion-type wear occurred to samples with intermediate phenolic contents (R4, R5 and R6).