Abstract: The construction of hierarchical thermoplastic polyurethane (TPU) composites with superior flame retardant and electromagnetic shielding capabilities hold significant practical importance. In this work, TPU composites loaded with a multilayer core-shell flame retardant (APP@CoAl-LDH@Si) and a modified conductive nanofiller (MWCNT-NH₂-PA) were firstly prepared through the melt blending method, acting as surface layer. Additionally, multilayered MXene films functionalized by bacterial cellulose (BC) and dopamine hydrochloride (DA) were fabricated via a facile and efficient vacuum filtration approach. Finally, a PBM film was utilized as an intermediate layer to construct hierarchical TPU composites. The results indicated that the introduction of 10 wt% APP@CoAl-LDH@Si hybrid, the peak heat release rate, total heat release, peak smoke production rate, and total smoke release of the TPU composites were decreased by 83.0 %, 61.3 %, 48.5 % and 66.9 %, respectively, compared with those of pure TPU due to the free radicals capture effect of APP, and the flame-retardant functions of LDH and silane. Moreover, the hierarchical TPU/APP@CoAl-LDH@Si/CP1-PBM exhibited excellent electromagnetic shielding performance, achieving 43.6 dB in the X-band because of multiple reflection losses, interface polarization losses, and charge carrier movement-induced thermal dissipation. Extraordinarily, the A and R coefficients were reversed in the X and K bands. This phenomenon was attributed to the different degrees of confinement of the multilayer structure to electromagnetic waves with different wavelengths. This work presents a novel model for the design and preparation of high-performance polymer composites with multiple properties and regulation mechanism.

Key words: Hierarchical structure, Flame retardancy, Electromagnetic shielding, Air assisted hot-pressing, Flexible characteristic