Influence of plasma pre-treatment of polytetrafluoroethylene (PTFE) micropowders on the mechanical and tribological performance of Polyethersulfone (PESU)-PTFE composites

Tribological and mechanical properties of Polyethersulfone (PESU) composites, containing pristine and plasma modified polytetrafluoroethylene (PTFE) micro-powders as solid-lubricants have been investigated. Low pressure 2.45 GHz microwave plasma functionalisation of PTFE powders was carried out using H2 and NH3 as process gases to introduce functional polar groups on the PTFE surfaces to enhance their wettability and mixing with PESU. As compared to pristine PTFE (F/C atomic ratio 1.86), X-ray photoelectron spectroscopy analysis confirmed the significant deflourination for both the NH3 (F/C atomic ratio 1.13) and H2 (F/C atomic ratio 1.30) plasma treated samples along with the attachment of polar surface moieties. An increase in the interaction between the plasma functionalised PTFE powders with PESU matrix was confirmed based on an increase in the glass transition temperature of the PESU-PTFE composites. The plasma treated PTFE-PESU composites exhibited nearly 75% higher force absorption capabilities (3.3 kN) than their pristine PTFE-PESU counterparts (0.96 kN). Moreover, the plasma treated PTFE-PESU composites exhibited a wear rate (3.42±0.51×10−06 mm3/Nm) which was nearly half of that of pristine PTFE-PESU composites (5.75±0.80×10−06 mm3/Nm). Thus, low-pressure microwave plasma modification offers an efficient route for surface functionalisation of solid lubricants, like PTFE, for enhanced dispersion in high-performance polymers.