Unraveling the micro-mechanisms of direct forming in polyimides: A multiscale study on sintering behavior and tribological performance

This study establishes a comprehensive, multiscale framework for the direct forming of high-performance polyimide components through integrated experiments and molecular dynamics (MD) simulations. The research systematically investigates the effects of cold-pressing pressure, sintering parameters, and atmosphere on structural evolution and final performance. MD simulations reveal the atomic-scale mechanisms, identifying an optimal cold-pressing window near 450 MPa that maximizes interfacial adhesion via van der Waals and electrostatic forces while preventing over-compaction damage. The sintering process is governed by thermally activated chain interdiffusion, with a protective nitrogen atmosphere proving critical to suppress oxidative degradation and achieve superior compressive strength (233 MPa) and ductility. Utilizing these optimized parameters, the tribological performance under dry sliding conditions is evaluated, identifying an optimal regime at intermediate sliding speeds and sub-yield loads characterized by stable friction and mild wear. This work provides a fundamental, atomic-scale guided strategy for the science-based manufacturing of polyimides with tailored mechanical and tribological integrity. • Integrates molecular dynamics with experiments to reveal the micro-mechanisms of polyimide direct forming. • Identifies an optimal cold-pressing window that balances densification and avoids defect formation. • Demonstrates the critical role of a protective sintering atmosphere in achieving superior mechanical properties. • Defines an optimal dry-sliding regime for minimal wear, linking processing conditions to tribological performance.