The effect of rare earths (RE) surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil-lubricated condition was investigated. Experimental results revealed that RE treated CF reinforced PTFE (CF/PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that, after RE treatment, oxygen concentration increased obviously, and the amount of oxygen-containing groups on CF surfaces were largely increased. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix. With strong interfacial adhesion of the composite, stress could be effectively transmitted to carbon fibers; carbon fibers were strongly bonded with PTFE matrix, and large scale rubbing-off of PTFE be prevented, therefore, tribological properties of the composite was improved.
Tribological properties of polytetrafluoroethylene(PTFE) composites filled with differently surface treated carbon fibers(CF),sliding against GCr15 steel under dry sliding conditions,were investigated on a block-on-ring M-2000 tribometer.Experimental results reveal that rare earths(RE) surface treatment reduces the friction and wear of CF-reinforced PTFE(CF/PTFE) composites.Scanning electron microscopy(SEM) investigation of worn surfaces of CF/PTFE composites shows that cracks or pores are visible on the worn surfaces of untreated and air-oxidated composite,while no crack and very few pores present on the worn surface of REtreated composite.The fiber-friction-angling effect makes carbon fibers angled and oriented along the frictional shearing force,and finally parallel to the friction surface,which makes interfacial adhesion become a key factor to tribological properties of CF/PTFE composite.With strong interfacial adhesion between carbon fiber and PTFE after RE surface treatment,carbon fibers are not easily detachable from the PTFE matrix in the process of fiber-friction-angling,which prevents the rubbing-off of PTFE,and accordingly improves the friction and wear properties of the composite.
Carbon fibers (CF) were surface treated with air-oxidation and rare earths (RE), respectively. The effect of RE surface treatment on tensile strength and tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites was investigated. Experimental results revealed that RE was superior to air oxidation in improving the tensile strength, elongation, and the tensile modulus of CF reinforced PTFE (CF/PTFE) composite. Compared to the untreated and air-oxidated CF/PTFE composite, the RE treated composite had the lowest friction coefficient and specific wear rate under a given applied load and reciprocating sliding frequency. The RE treatment effectively improved the interfacial adhesion between CF and PTFE. With strong interfacial coupling, the carbon fibers carried most of the load, and direct contact and adhesion between PTFE and the counterpart were reduced, accordingly the friction and wear properties of the composite were improved.
