Effect of proton irradiation on the friction and wear properties of polyimide

• PI surface was carbonized after proton irradiation.
• TRIM simulation indicated that proton irradiation at 25 keV damage PI within 514 nm from the surface.
• Proton irradiation increased the initial friction coefficient and decreased the steady friction coefficient of PI.
• A transition from initial short adhesive wear to three-body abrasive wear was observed for proton irradiated PI.

Effect of 25 keV proton irradiation with fluence of 2.25×1017 ion/cm2 on the structural and tribological properties of polyimide blocks were investigated in a ground-based simulation facility. The changes in surface structure were characterized by FTIR-ATR, laser micro-Raman, contact angle measurement and nanoindentation. The experimental results indicated that the proton irradiation induced bond breaking to form the carbon-enriched structure on polyimide surface, and then increased the surface hardness and the surface energy. The irradiation depth was restricted within 514 nm from the surface by TRIM simulation.The carbonized layer induced by irradiation was worn out in friction test, which was proved through Raman spectra analysis of the wear track. Proton irradiation increased the initial friction coefficient and decreased the steady friction coefficient of polyimide. In the initial stage, the friction coefficient was closely related to surface hardness of material, and the main wear mechanism was adhesive wear. In the steady stage, the main wear mechanism was three-body abrasion wear, three-body abrasion and the low surface energy could reduce the wear rate and the friction coefficient.

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