Flexible and efficient electromagnetic interference (EMI) shielding polymer composite foams are rapidly developing, but it is difficult to avoid the deterioration of shielding properties after foaming. To solve the issue, in this work, composite foams with multivariate gradient structure of thermoplastic polyurethane (TPU) mixed with multiwalled carbon nanotubes (MWCNTs) were constructed by combining the soft-hard domains proportional gradient of TPU with filler content gradient. Gradient-structured TPU/MWCNTs foams with impedance matching layer and high reflector layer were obtained and impedance matching layer with large cells significantly reduced the density while high reflector layer with a few cells maintained relatively perfect conductive network, whose shielding efficiency was 38.2 % higher than that of unfoamed sample. Furthermore, TPU/MWCNTs composite foams presented great stability even after 1000 times bending. This special multivariate gradient structure shows potential applications in microelectronic devices and aerospace fields and is critical to the development of high-performance EMI shielding polymer foams.

中文翻译：

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柔性热塑性聚氨酯基复合泡沫的多元梯度结构设计，增强电磁干扰屏蔽性能


柔性高效的电磁干扰 （EMI） 屏蔽聚合物复合泡沫正在迅速发展，但发泡后屏蔽性能的恶化很难避免。为解决这一问题，本工作通过将TPU的软硬域比例梯度与填料含量梯度相结合，构建了热塑性聚氨酯（TPU）与多壁碳纳米管（MWCNT）混合的具有多变量梯度结构的复合泡沫塑料。获得了具有阻抗匹配层和高反射层的梯度结构 TPU/MWCNTs 泡沫，具有大单元的阻抗匹配层显著降低了密度，而具有少量单元的高反射层保持了相对完美的导电网络，其屏蔽效率比未发泡样品高 38.2 %。此外，TPU/MWCNTs 复合泡沫即使在 1000 次弯曲后也表现出极好的稳定性。这种特殊的多变量梯度结构在微电子器件和航空航天领域显示出潜在的应用，对于高性能 EMI 屏蔽聚合物泡沫的开发至关重要。