Mechanism of Synergistic Effect between PDA-PEI-Mediated Interface Bonding Optimization and Transfer Film Formation in Regulating the Tribological Properties of Aramid Particle/PTFE Composites

Aramid particles (AP) and polytetrafluoroethylene (PTFE) impart tribological application potential to AP/PTFE composites, but weak interfacial bonding and poor formation of high-quality transfer films hinder performance enhancement. In this study, AP was surface-functionalized using a simple, mild, eco-friendly polydopamine (PDA)-polyethylenimine (PEI) synergistic strategy to fabricate AP-PDA-PEI/PTFE composites. Systematic investigations were conducted on their microscopic mechanical properties, tensile strength, tribological performance, and underlying mechanisms. Results indicate that PDA-PEI modification enhances the interfacial microscopic mechanical properties between AP and PTFE. Compared to AP/PTFE, the modified composite’s interfacial modulus is increased by 89.67%. AP 10 -PDA-PEI/PTFE exhibits a tensile strength of 35   MPa, 59.1% higher than AP 10 /PTFE. Characterizations of interfacial microtopography and elemental distribution confirm enhanced interfacial bonding. At 3   MPa, 6.5   MPa, and 10   MPa, AP 10 /PTFE has average friction coefficients of 0.185, 0.157, and 0.150, respectively, with wear rates of ~10 -6 mm 3 /(N·m). In contrast, AP 10 -PDA-PEI/PTFE shows optimal tribological performance: its average friction coefficients are reduced by 15.1%, 12.0%, and 30.2%, with wear rate decreased to ~10 -7 mm 3 /(N·m) (one order of magnitude lower than unmodified AP 10 /PTFE). Wear scar and transfer film characterizations reveal that the composite’s excellent performance stems from the synergy of optimized interfacial bonding and transfer film formation. Enhanced interfacial bonding inhibits AP debonding, while transfer film formation facilitates tribochemical reactions. This transforms the sliding contact mode to tribofilm-transfer film contact, achieving stable, low-wear lubrication.