Interface engineering enhances thermal conduction and electromagnetic shielding in aramid composites.

High thermal conductivity and electromagnetic interference (EMI) shielding are vital in complex thermal management. Aramid is suitable for applications in extreme environments, but enhancing thermal conductivity and EMI shielding simultaneously remains challenging. This study reports a universal interface engineering strategy using hydroxyl-modified carbon nanotubes (OH-CNTs) to achieve this combination in aramid composites. Simulations reveal that hydroxylation enhances low-frequency phonon transmission, reducing the interface thermal resistance by 62% for OH-CNT/OH-CNT interfaces and 86% for OH-CNT/aramid interfaces. Hydroxyl modification introduces dipole polarization, enhances interface polarization, and promotes filler dispersion. The developed OH-CNT-40% film achieves an in-plane thermal conductivity of 33.7 W m-1 K-1 and an EMI shielding effectiveness of 819 dB cm-1, surpassing the results of most previous studies. Interface engineering enables simultaneous enhancement of thermal conductivity and EMI shielding, offering a universal design principle for next-generation multifunctional thermal interface materials.