石墨烯/四氧化三铁纳米复合物的选择性分散对聚合物发泡材料电磁屏蔽性能的影响机制

Cellular structure endows conductive polymer composite with lightweight and the improved absorption of elctromagnetic energy. However, the introdution of cellular structure decreases the volume fraction of electromagnetic interference shielding agent (EMISA), which usually decrease the EMI shielding effectiveness (SE) of polymer composite. Therefore, the development of polymer composite with both improved SE and SEA becomes a hot reseach topic in new material field. Theoretical analysis shows that the increased SE can be achieved in polymer composite foam by adjusting the dispersion state of EMISA, but the cell nucleation and growth processes of the conventional polymer chemical and physical foaming are difficult to be controlled because of their fast nature, leading to the formation of irregular dispersion state of EMISA in matrix. In this project, the typical polymer foaming systems are selected, a novel solvent induced phase separtion foaming method is used to prepare polyimide (PI)/Graphene@Fe3O4 (G@Fe3O4) composite foams by controlling the types of coagulation bath, the strength and treatment time of external megnetic field, and by applying the co-imidization action method of multilayered foamed polyimide acid (PAA)/G@Fe3O4 sheets. These strategies lead to the orientated state of G@Fe3O4 around cell walls, the gradient state across PAA amd PI foam, the locally enriched state in PAA and PI foam, and the signal and double gradient combination states in PI foams. Based on the prepared samples, the project will investigate the influence of selective dispersion states of G@Fe3O4 on the SE and the EMI shileding mechanism of PAA and PI composite foams, which will help us to deeply understand the strategies to obtain polymer composite foam with the improved EMI properties.

发泡结构赋予导电型聚合物复合材料轻量化的结构，显著增加的电磁波吸收损耗，不过，体积膨胀往往降低了复合材料的总电磁屏蔽效能。理论分析表明通过调控电磁屏蔽剂在聚合物复合发泡材料中的分散状态有望提高材料的电磁屏蔽效能，不过，传统的聚合物化学和物理发泡过程中发泡时间很短，泡孔的成核和增长过程难以有效控制，电磁屏蔽剂通常无规地分散在所制备的发泡材料中。本项目拟选择典型聚合物复合材料发泡体系，采用新颖的溶剂诱导相分离发泡技术，通过控制凝固浴氛围、外加磁场强度和作用时间以及通过层叠聚酰亚胺酸复合发泡薄膜共亚胺化反应等手段，制备石墨烯/四氧化三铁（G@Fe3O4）纳米复合物绕泡孔取向分散、梯度分散、局部富集分散以及单梯度、双梯度组合分散的一体化聚酰亚胺复合发泡材料，探讨G@Fe3O4的选择性分散状态对复合发泡材料电磁屏蔽效能和电磁屏蔽机制的影响，探索提高聚合物复合发泡材料电磁屏蔽性能的途径。

发泡结构赋予导电型聚合物复合材料轻量化的结构，显著增加的电磁波吸收损耗，不过，体积膨胀往往降低了复合材料的总电磁屏蔽效能。理论分析表明通过调控电磁屏蔽剂在聚合物复合发泡材料中的分散状态有望提高材料的电磁屏蔽效能，不过，传统的聚合物化学和物理发泡过程中发泡时间很短，泡孔的成核和增长过程难以有效控制，电磁屏蔽剂通常无规地分散在所制备的发泡材料中。本项目采用相分离制孔、层叠深度相分离、模板制孔、薄膜弯折、碳化烧结等多种方法制备了聚合物/石墨烯复合微发泡薄膜、具有梯度结构和三明治结构的聚合物复合微孔薄膜、具有锯齿状的聚合物复合薄膜、中空多孔碳膜管，研究了宏观结构和微观孔结构对复合发泡材料电磁屏蔽效能和电磁屏蔽机制的影响，探索了提高聚合物复合发泡材料电磁屏蔽性能的途径。