Abstract Percolation behavior of electrical conduction that is related to the formation of conductive networks has been well demonstrated in conductive polymer composites (CPC). However, the electromagnetic interference (EMI) shielding of CPC is normally very low at the percolation threshold due to the different mechanism. Here, we first predicted the percolation behavior of EMI shielding existing in CPC because the EMI shielding effectiveness (SE) was mainly dependent on the conductivity of CPC if assuming the constantly magnetic permeability. In practice, we also found the percolation behavior of EMI shielding in the multi-walled carbon nanotube (MWCNT) filled poly( l -lactide) (PLLA) with good dispersion and isotactic polypropylene (iPP) with poor dispersion. Furthermore, the percolation threshold of EMI shielding was higher than the percolation threshold of electrical conduction. The percolation thresholds of EMI shielding and electrical conduction were ∼2.00 and ∼0.40 vol% for PLLA/MWCNT nanocomposites, and ∼5.40 and ∼1.40 vol% for iPP/MWCNT nanocomposites, respectively. The SEM and TEM image shows the sparse and dense MWCNT network near the percolation threshold of electrical conduction and EMI shielding, respectively, indicating that the sparse network of MWCNT can create high electrical conductivity as long as the formation of conductive paths. However, the high performance EMI shielding requires dense network of MWCNT.

中文翻译：

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聚合物/多壁碳纳米管纳米复合材料中电磁干扰屏蔽的渗透行为

摘要 在导电聚合物复合材料 (CPC) 中已经很好地证明了与导电网络形成相关的导电渗透行为。然而，由于机制不同，CPC 的电磁干扰 (EMI) 屏蔽在渗透阈值下通常非常低。在这里，我们首先预测了 CPC 中存在的 EMI 屏蔽的渗透行为，因为如果假设磁导率恒定，则 EMI 屏蔽效率（SE）主要取决于 CPC 的电导率。在实践中，我们还发现了具有良好分散性的多壁碳纳米管 (MWCNT) 填充的聚 (l-丙交酯) (PLLA) 和分散性较差的全同立构聚丙烯 (iPP) 中的 EMI 屏蔽的渗透行为。此外，EMI屏蔽的渗透阈值高于导电的渗透阈值。对于 PLLA/MWCNT 纳米复合材料，EMI 屏蔽和导电的渗透阈值分别为~2.00 和~0.40 vol%，对于 iPP/MWCNT 纳米复合材料，分别为~5.40 和~1.40 vol%。SEM和TEM图像分别显示在导电和EMI屏蔽的渗透阈值附近稀疏和密集的MWCNT网络，表明只要形成导电路径，MWCNT的稀疏网络就可以产生高导电性。然而，高性能的 EMI 屏蔽需要 MWCNT 的密集网络。iPP/MWCNT 纳米复合材料分别为 40 vol%。SEM和TEM图像分别显示在导电和EMI屏蔽的渗透阈值附近稀疏和密集的MWCNT网络，表明只要形成导电路径，MWCNT的稀疏网络就可以产生高导电性。然而，高性能的 EMI 屏蔽需要 MWCNT 的密集网络。iPP/MWCNT 纳米复合材料分别为 40 vol%。SEM和TEM图像分别显示在导电和EMI屏蔽的渗透阈值附近稀疏和密集的MWCNT网络，表明只要形成导电路径，MWCNT的稀疏网络就可以产生高导电性。然而，高性能的 EMI 屏蔽需要密集的 MWCNT 网络。