Electromagnetic interference shielding effectiveness of microcellular polyimide/in situ thermally reduced graphene oxide/carbon nanotubes nanocomposites

摘要

Highlights•Graphene Oxide (GO) and multi-walled carbon nanotubes (MWCNTs) could be uniformly dispersed in poly (amic acid) (PAA, precursor of polyimide) solution. While PAA was thermally imidized into polyimide (PI), the GO in PAA matrix was in situ reduced into reduced graphene oxide (RGO). This made RGO and MWCNTs uniformly dispersed in PI matrix.•The microcellular PI/RGO/MWCNTs nanocomposites were obtained through solvent evaporation induced phase separation.•The synergistic effect between RGO and MWCNTs enhanced both the electrical conductivity and electromagnetic interference (EMI) shielding performance of the microcellular nanocomposites.AbstractA simple and effective method was adopted to fabricate microcellular polyimide (PI)/reduced graphene oxide (GO)/multi-walled carbon nanotubes (MWCNTs) nanocomposites. Firstly, microcellular poly (amic acid) (PAA)/GO/MWCNTs nanocomposites were prepared through solvent evaporation induced phase separation. In this process, PAA and dibutyl phthalate (DBP) co-dissolved in N,N-dimethylacetamide (DMAc) underwent phase separation with DMAc evaporating, and DBP microdomains were formed in continuous PAA phase. Subsequently, PAA was thermally imidized and simultaneously GO was in situ reduced. After DBP was removed, the microcellular PI/reduced GO (RGO)/MWCNTs nanocomposites were finally obtained. When the initial filler loading was 8wt%, the electrical conductivity of microcellular PI/RGO, PI/MWCNTs and PI/RGO/MWCNTs nanocomposites were 0.05, 0.02 and 1.87S·m−1, respectively, and the electromagnetic interference (EMI) shielding efficiency (SE) of microcellular PI/RGO, PI/MWCNTs and PI/RGO/MWCNTs nanocomposites were 13.7–15.1, 13.0–14.3 and 16.6–18.2dB, respectively. The synergistic effect between RGO and MWCNTs enhanced both the electrical conductivity and EMI shielding performance of the microcellular PI/RGO/MWCNTs nanocomposites. The dominating EMI shielding mechanism for these materials was microwave absorption. While the initial loading of GO and MWCNT was 8wt%, the microcellular PI/RGO/MWCNTs nanocomposite (500μm thickness) had extremely high specific EMI SE value of 755–823dB·cm2·g−1. Its thermal stability was also obviously improved, the 5% weight loss temperature in nitrogen was 548°C. In addition, it also possessed a high Young’s modulus of 789MPa.