In this study, the thermoplastic polyurethane (TPU)/multiwalled carbon nanotubes (MWCNTs) lightweight flexible foam with sandwich structure was achieved by supercritical carbon dioxide (scCO₂) foaming. This work studied the relationship between foaming behavior and electromagnetic interference (EMI) shielding performance. The results showed that the formation of cell structure could not only achieve the purpose of lightweight, but also control the position of electromagnetic interference shielding efficiency (EMI SE) peak by adjusting foaming temperatures. The EMI SE peak could shift to high frequencies as the foaming temperature increases, and the adjustable frequency ranged from 9.76 GHz to 14.72 GHz. The maximum EMI SE of TPU/MWCNTs composite foams increased to 44.86 dB under 2.5 wt% filler content with a density of 0.61 g/cm³. This work provided a feasible idea for the preparation of lightweight and adjustable frequency-selective EMI shielding composite materials by supercritical fluid foaming.

本研究采用超临界二氧化碳（scCO ₂) 起泡。这项工作研究了发泡行为与电磁干扰 (EMI) 屏蔽性能之间的关系。结果表明，泡孔结构的形成不仅可以达到轻量化的目的，还可以通过调节发泡温度来控制电磁干扰屏蔽效率（EMI SE）峰值的位置。随着发泡温度的升高，EMI SE 峰值可能会向高频移动，可调频率范围为 9.76 GHz 至 14.72 GHz。^{在密度为 0.61 g/cm 3}的 2.5 wt% 填料含量下，TPU/MWCNTs 复合泡沫的最大 EMI SE 增加到 44.86 dB. 该工作为超临界流体发泡制备轻质可调的选频EMI屏蔽复合材料提供了可行的思路。