Effect of filler surface properties on structure, mechanical and tribological behavior of PTFE-carbon black composites

Effect of two grades of carbon black (CB) on structure, strength and tribological behavior of PTFE-CB composites is studied in the filler range of 10 mass%. It is found that differences in surface properties of the fillers used to determine the type of supermolecular structure evolved and patterns of variation of mechanical properties, friction and wear in response to increasing filler content. It is found that wear of low-filled PTFE-CB composites is dominated by delamination mechanism and wear resistance changes correlate with structural transformations of the composites. The maximum increase in wear resistance of the PTFE composites is reached at 1 mass% filling for both filler grades amounting to the factor of ∼40 for the CB grade with low surface activity and small specific surface area and a factor of ∼700 for the CB grade with high activity and high value of the specific surface area. It is first found that relative wear resistance increases in proportion to the specific surface area and, tentatively, activity of the surface centers of the CB filler used, which fact is attributed to the filler capacity to block and heal fatigue-induced cracking of the subsurface layer at friction.