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

ABSTRACT 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.