A large number of electronic devices could generate a lot of electromagnetic waves, which could interfere with other equipment and harm the human body. Therefore, an electromagnetic interference shielding (EMI) material is urgently needed to protect the human body and the electronic equipment. In this paper, the multi-wall carbon nanotubes (MWCNTs) and the nano-Fe₃O₄ were added into the polylactic acid (PLA) matrix to form the composite film with electromagnetic interference shielding performance. And the structure and properties of MWCNTs/Fe₃O₄/PLA composite films, such as the morphology, chemical structure, crystallization, mechanical property, conductive property, magnetic property and electromagnetic interference shielding property, were researched. The result shows that too much Fe₃O₄ could lead to agglomeration, and the coupling agent KH570 had grafted and modified the surface of MWCNTs. The MWCNTs and nano-Fe₃O₄ could increase the crystallinity of PLA matrix. With the increase of MWCNTs, the maximum tensile stress of composite films gradually increased, and the maximum tensile strain decreased, and the resistance value showed a significant downward trend. The Fe₃O₄ could improve the magnetic properties of composite film. The MWCNTs and Fe₃O₄ could improve the electromagnetic interference shielding efficiency (EMI SE). The MWCNTs played a more significant role than the Fe₃O₄ in the process of EMI, and the EMI SE of the composite film with 3:1 ratios of MWCNTs/Fe₃O₄ could rise to 22 dB.

大量电子设备会产生大量电磁波，可能会干扰其他设备并伤害人体。因此，迫切需要电磁干扰屏蔽（EMI）材料来保护人体和电子设备。本文将多壁碳纳米管（MWCNTs）和纳米Fe ₃ O ₄加入聚乳酸（PLA）基体中，形成具有电磁干扰屏蔽性能的复合膜。MWCNTs / Fe ₃ O ₄的结构与性能研究了/ PLA复合膜的形貌，化学结构，晶化，力学性能，导电性能，磁性能和电磁干扰屏蔽性能。结果表明，过多的Fe ₃ O ₄会导致团聚，偶联剂KH570接枝并修饰了MWCNTs的表面。MWCNTs和纳米Fe ₃ O ₄可以提高PLA基质的结晶度。随着MWCNTs含量的增加，复合膜的最大拉伸应力逐渐增大，最大拉伸应变减小，电阻值呈现明显的下降趋势。铁₃ O ₄可以改善复合膜的磁性能。MWCNTs和Fe ₃ O ₄可以提高电磁干扰屏蔽效率（EMI SE）。在EMI过程中，MWCNTs的作用比Fe ₃ O ₄更为重要，MWCNTs / Fe ₃ O _4的比例为3：1的复合膜的EMI SE可以提高到22 dB。