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<p>Epoxy-based nanocomposites filled with two-dimensional materials such as graphene nanoplates (GNP), graphene oxide (GO), and molybdenum disulfide (MoS₂) are widely investigated for electromagnetic applications, including electromagnetic interference (EMI) shielding. In this work, epoxy nanocomposites containing 0–5 wt% of different 2D fillers were prepared and their complex dielectric permittivity was measured by a coaxial transmission/reflection method using a vector network analyzer. Particular attention is devoted to the experimental reliability of the extracted electromagnetic parameters and to the influence of environmental factors. While permittivity values significantly higher than literature benchmarks were measured, no systematic dependence on filler concentration was observed. A detailed analysis indicates that moisture absorption in the epoxy system, combined with experimental limitations inherent to broadband coaxial measurements, can dominate the dielectric response and mask filler-dependent trends. Focusing on the frequency range up to 5&#xa0;GHz, where the measurements are most stable, the experimental results are shown to be consistent with a simple effective-medium model that includes a third phase associated with absorbed water. The estimated moisture content required to account for the observed permittivity enhancement is on the order of 10 wt%. These findings highlight the critical role of moisture control and measurement setup in the electromagnetic characterization of epoxy-based nanocomposites and provide cautionary guidelines for the interpretation of permittivity data and their use in EMI shielding assessment.</p>

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Critical assessment of dielectric permittivity measurements in epoxy nanocomposites based on two-dimensional fillers

  • 期刊论文

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  • 发表日期：

    2026年8月1日

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  • S. Bellucci

摘要

Epoxy-based nanocomposites filled with two-dimensional materials such as graphene nanoplates (GNP), graphene oxide (GO), and molybdenum disulfide (MoS₂) are widely investigated for electromagnetic applications, including electromagnetic interference (EMI) shielding. In this work, epoxy nanocomposites containing 0–5 wt% of different 2D fillers were prepared and their complex dielectric permittivity was measured by a coaxial transmission/reflection method using a vector network analyzer. Particular attention is devoted to the experimental reliability of the extracted electromagnetic parameters and to the influence of environmental factors. While permittivity values significantly higher than literature benchmarks were measured, no systematic dependence on filler concentration was observed. A detailed analysis indicates that moisture absorption in the epoxy system, combined with experimental limitations inherent to broadband coaxial measurements, can dominate the dielectric response and mask filler-dependent trends. Focusing on the frequency range up to 5 GHz, where the measurements are most stable, the experimental results are shown to be consistent with a simple effective-medium model that includes a third phase associated with absorbed water. The estimated moisture content required to account for the observed permittivity enhancement is on the order of 10 wt%. These findings highlight the critical role of moisture control and measurement setup in the electromagnetic characterization of epoxy-based nanocomposites and provide cautionary guidelines for the interpretation of permittivity data and their use in EMI shielding assessment.