The Role of Microstructure in Ultralow Wear Fluoropolymer Composites

Abstract

Past studies have shown that the inclusion of fillers in a polytetrafluoroethylene (PTFE) matrix can improve wear resistance by nearly four orders of magnitude. These discoveries have prompted several tribological experiments over the past decade that have highlighted the importance of particle size, tribofilm formation, filler percentage, and environment. To evaluate the effect that microstructure plays on a composite’s tribological performance, PTFE-filled polyamide-imide (PAI) composites were made and tested. To investigate the role of microstructure on the tribological performance of fluoropolymer composites, 12 composite formulations of PTFE and PAI over a range of 0 to 100 vol% PAI were tested. PTFE–PAI composite samples were slid against a stainless steel countersample using a linear reciprocating tribometer under a nominal 6.35 MPa contact pressure at 50.8 mm/s sliding speed. Of the samples tested, the 25 vol% PAI showed a remarkable mean steady-state wear rate of k = 3 × 10⁻⁹ mm³/Nm over an extreme distance of 360 km. A serial imaging investigation revealed that a mechanical interlocking of the two polymers occurred during the sintering process, which possibly contributed to the ultralow wear rates observed in this polymer–polymer composite.

Keywords:

• Self-lubricating composites
• wear mechanisms
• friction test methods
• PTFE