Dual Self-Healing and Self-Lubricating Properties of Microcapsules/Polyimide-Based Composites

Polyimide (PI) is widely used in high-end engineering sectors, including aerospace and defense, due to its exceptional mechanical properties. However, pristine PI exhibits critical limitations during service, including a high coefficient of friction, severe wear, and mechanically induced microcrack formation. In this study, melamine-urea-formaldehyde (MUF) was used as the shell material and E-51 (Ep) as the core material to synthesize MUF@Ep microcapsules via an in situ polymerization method. The microcapsules were then incorporated into a PI matrix to fabricate multifunctional composites exhibiting both self-healing and self-lubricating properties. The tribological properties were systematically evaluated as functions of microcapsule content and applied load using a ball-on-disk reciprocating tester. The results showed that the composite containing 4.5 wt% microcapsules exhibited optimal performance at 30 N, with the coefficient of friction and volumetric wear rate reduced by 24.44% and 45.68%, respectively, compared with pristine PI. After heating at 150°C for 60 min, self-healing of the damaged area was achieved. During multi-cycle in situ friction-healing tests, the samples exhibited excellent tribological performance and wear healing under friction conditions, achieving a maximum healing efficiency of 41.42%. Therefore, the MUF@Ep/PI-based composites demonstrated superior tribological performance and reliable self-healing capability. This study provides a viable strategy for high-end engineering applications and for the design of adaptive intelligent materials suitable for complex service environments. Highlights Developed composites with self-healing and self-lubricating functions. Epoxy resin serves as both a lubricant and a healing agent. Self-healing achieved without additional curing agents. Realize the self-healing of friction-induced abrasion marks.