Lightweight Double‐Layered Polylactic Acid‐Based Nanocomposite Foams for Highly Absorption‐Dominated Electromagnetic Shielding

Lightweight polymer nanocomposites with efficient electromagnetic interference (EMI) shielding properties play a crucial role in mitigating pollution caused by electromagnetic radiation. In this work, a combination of melt mixing and supercritical carbon dioxide (scCO2) is used to fabricate lightweight, high‐performance polylactic acid (PLA)‐based conductive nanocomposite foams, with absorption as the dominant shielding mechanism. The addition of carbon nanostructures (CNS) significantly improves the rheological and foaming properties of the PLA‐based nanocomposites. Notably, when the CNS content is 1 wt%, the expansion ratio of the PLA‐based nanocomposite foam reaches its peak at ≈43.5. Additionally, with 4 wt% CNS, the specific electromagnetic shielding effectiveness of the foam reaches up to 179.0 dB cm−2 g−1. To further enhance the absorption of electromagnetic waves, the shielding mechanism of the double‐layer structure consisting of 1% and 6% is absorption‐dominated with an absorption coefficient of 0.67. The specific electromagnetic shielding effectiveness reaches up to 150.7 dB cm−2 g−1. This work offers a straightforward and eco‐friendly approach for the facile preparation of lightweight electromagnetic interference shielding material.