Journal of Polymer & Composites Original Research Open Access
Absorption-Dominated EMI Shielding in Benzoxazine/Epoxy Nanocomposites Reinforced with Graphene Oxide and Zinc Oxide
Abstract
Benzoxazine monomer was synthesized via a Mannich condensation reaction from phenolic and amine precursors, followed by thermal curing to form a crosslinked polybenzoxazine network for advanced composite applications. Electromagnetic interference (EMI) shielding materials based on lightweight polymer nanocomposites have attracted significant attention for advanced electronic applications. In this study, benzoxazine/epoxy nanocomposites reinforced with graphene oxide (GO) and zinc oxide (ZnO) at loadings of 5 and 10 wt% were prepared and evaluated. Electrical conductivity measurements revealed a marked decrease in sheet resistance from 9.0 × 10⁷ Ω/sq for the pure matrix to 5.0 × 10⁴ Ω/sq for the GO 10 wt% composite, suggesting the formation of conductive pathways. In contrast, ZnO-filled composites showed only limited improvement in conductivity, consistent with their semiconducting nature. The EMI shielding effectiveness (SE) was investigated in the X-band frequency range (8–12 GHz) using a vector network analyzer. The GO 10 wt% composite achieved an average SE of approximately 19.6 dB, compared to ~16 dB and ~15 dB for GO 5 wt% and ZnO-based composites, respectively. Analysis of shielding components indicated that absorption (SEA) appears to be the dominant mechanism, while reflection (SER) remains relatively low. A practical EMF shielding test demonstrated a significant reduction in transmitted power density in the presence of the nanocomposites, supporting the trends observed in VNA measurements. However, these measurements are considered qualitative due to instrumental limitations. Overall, the results indicate that GO-reinforced benzoxazine/epoxy nanocomposites provide enhanced EMI shielding performance primarily governed by absorption mechanisms.
Keywords
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