Unraveling the Impact of Forming Strategies and Sintering Atmospheres on the Tribological Performance of Polyimide

ABSTRACT Conventional design of polymer tribomaterials assumes higher bulk mechanical strength improves wear resistance, but this empirical rule does not always hold due to processing‐induced microstructural heterogeneities, particularly interparticle interfaces governing dry sliding failure. Herein, polyimide samples were prepared by hot compression molding (HCM) and direct forming (DF) in air or nitrogen. Mechanical testing, multicondition tribological evaluation, and atomistic simulations were combined to establish the process–structure–property relationship. Results reveal a pronounced mechanical‐wear paradox, where nitrogen‐sintered DF PI exhibits lower tensile strength than HCM PI, but achieves a lower specific wear rate and reduced maximum frictional interface temperature under identical sliding conditions. Mechanistic analysis shows that the inert nitrogen atmosphere suppresses thermal oxidative degradation and enables robust, ductile interparticle bonding. This interfacial integrity reduces interfacial shear and frictional heat, facilitating a thin, stable protective transfer film on the counterface. In contrast, the fully dense, HCM PI suffers severe adhesive wear driven by frictional surface softening. Atomistic simulations further corroborate that chain interdiffusion and interfacial healing during inert sintering are the atomistic origin of the improved tribological performance. These findings revise the conventional strength‐centric design logic for polyimide tribocomponents and provide science‐based guidance for forming strategy selection in high‐performance friction applications.