低熔体粘度聚合物中导电粒子聚集分布与电磁屏蔽性能研究

Compared with conventional conductive polymer composites (CPCs), the formation of segregated structure via the controllable distribution of electrical fillers in CPCs is beneficial to achieve higher electromagnetic interference shielding effectiveness (EMI SE). Nevertheless, the reported segregated CPCs were mainly basically on high-melt-viscosity polymers (e.g., ultrahigh molecular polyethylene, natural rubber, etc.) or low-temperature/pressure processed amorphous polymers (e.g., polycarbonate, polystyrene, etc.), while for low-melt-viscosity semicrystalline polymers (polyphenylene sulfide PPS, polyethyleneterephthalate, etc.) it is challenged to form segregated structure because of the strong molecular motion favoring the diffusion of conductive fillers into the their interior. Moreover, the achievement of high EMI SE and low reflectivity simultaneously is always contradictory. In this work, we aim to utilize the sintering molding method to fabricate the segregated carbon nanotube (CNT)/graphene oxide@Fe3O4 (G@Fe)/PPS composites, where PPS was selected as the model polymer matrix for its low melt viscosity and in great need for shielding field of aerospace, electronics, and transportation. The developed segregated structure with G@Fe uniformly dispersed in the interior of PPS domains and CNT selectively distributed at the interfaces of G@Fe/PPS domains would combine the high dissipation capacity of G@Fe and the high electrical conductivity of CNT effectively, which is in favor of achieving high EMI SE and low reflectivity in the resultant CNT/G@Fe/PPS composite. The dependence of segregated structure on EMI shielding performance of the composite will be established. Furthermore, the EMI shielding mechanism of the composite will be analyzed to reveal the intrinsic mechanism why the formation of segregated structure would result in high EMI SE and low reflectivity, according to the Schelkunoff principle and transmission line theory. Our work will provide theoretical guidance and experimental support for the application of segregated CPCs in the field of high-performance EMI shielding.

成型加工过程中控制导电聚合物复合材料（CPCs）内部导电粒子聚集分布，获得的隔离结构CPCs相比普通CPCs有更高电磁屏蔽效能（EMI SE），但目前局限于超高熔体粘度聚合物和非晶聚合物，且存在高EMI SE和低反射率难以平衡问题，限制其应用。本项目拟通过模压烧结成型方法在低熔体粘度半晶聚合物（聚苯硫醚，PPS）中调控碳纳米管（CNT）聚集分布形态以构筑隔离结构导电网络，同时在PPS微区内部引入铁磁性石墨烯@Fe3O4纳米粒子（G@Fe），实现CNT高电导和G@Fe高电磁波耗散能力的协同效应，获得同时具有高EMI SE和低反射率的CNT/G@Fe/PPS复合材料。深入研究复合材料隔离结构形态与电磁屏蔽性能关系，结合Schelkunoff原理和传输线理论分析电磁屏蔽机理，弄清复合材料获得高EMI SE和低反射率的内在机理，为高性能电磁屏蔽用隔离结构CPCs研究提供理论基础和实验依据。

聚合物导电复合材料（CPCs）内部构建隔离结构导电网络，有利于获得高电磁屏蔽效能。然而，对于低熔体粘度聚合物复合材料，如聚苯硫醚等，成型过程中导电粒子极易与聚合物基体分子链相互扩散，导电粒子无法在聚合物微区界面分布形成隔离结构导电网络。本项目通过引入烧结成型新方法在典型低熔体粘度聚合物聚苯硫醚（PPS）内部构建了隔离结构碳纳米管（CNT）导电网络。复合材料在低CNT含量下获得高电磁屏蔽效能，且能同时保持聚合物基体本征耐热性，为高电磁屏蔽性能和高耐热复合材料制备提供了新思路。在此基础上，本项目探讨了在PPS基体中利用银-硫（Ag-S）配位反应诱导原位界面增强策略构建高效隔离结构Ag导电网络的可能性，并通过设计纳米银颗粒包覆PPS粒子的前驱核-壳结构粒子，采用热压成型手段成功获得了同时兼具超高效屏蔽性能、良好导热性能和机械性能、优异耐磨性能、耐溶剂性能、阻燃性能和抗菌性能等多功能的Ag/PPS电磁屏蔽复合材料，为设计应对苛刻工作环境的高性能电磁屏蔽复合材料提供了新的研究策略。基于隔离结构导电网络在电磁屏蔽材料方面的优势，本项目将隔离结构拓展到多孔导电聚合物复合材料，尝试将取向冷冻干燥技术与密度诱导填料分离的控制方法相结合，提出了在泡孔结构中构筑非对称导电网络的设计新策略，实现了对CPCs电磁响应特征与吸收反射屏蔽机制的有效调控，研制了具有轻质、高电磁屏蔽效能和低电磁波反射特征的电磁屏蔽复合材料。为推进高性能CPCs屏蔽材料在下一代智能电子设备安全、可靠、绿色电磁防护中的应用提供了理论基础和实验参考。