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<p>Waterborne epoxy varnishes are essential for electrical steel laminates used in electric engines or generators. Two varnish formulations based on bisphenol-A-diglycidylether and dicyandiamide with an epoxy equivalent weight (EEW) of ~ 500 and ~ 900&#xa0;g/mol were investigated. Thin specimens were prepared by consecutive coating and solvent evaporation followed by final curing. Glass transition temperatures (<i>T</i><sub><i>g</i></sub>) of 89&#xa0;°C (EEW-900) and 101&#xa0;°C (EEW-500) were deduced by dynamic mechanical analysis (DMA). The lower <i>T</i><sub><i>g</i></sub> value was attributed to the higher EEW and a lower network density. Moreover, master curves along with Williams–Landel–Ferry and Prony series parameters were generated. By digital image correlation (DIC)-assisted tensile testing of single epoxy films at temperatures from 30 to 150&#xa0;°C, a significant drop in tensile modulus from 2600 to 10&#xa0;MPa and a rise in Poisson’s ratio from 0.35 to 0.47 was ascertained. The implemented finite element model (FEM) showed a good agreement with the experimental data. </p> Graphical Abstract <p></p>

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Simulation of steel/epoxy laminates for electric engines or generators: Part 1—Characterization and modeling of coating films based on waterborne epoxy varnishes

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年6月16日

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  • Martin Tiefenthaler,
  • Gernot M. Wallner,
  • Cornelia Marchfelder,
  • Alexander Lovas,
  • Bernhard Strauß,
  • Martin Rosner

摘要

Waterborne epoxy varnishes are essential for electrical steel laminates used in electric engines or generators. Two varnish formulations based on bisphenol-A-diglycidylether and dicyandiamide with an epoxy equivalent weight (EEW) of ~ 500 and ~ 900 g/mol were investigated. Thin specimens were prepared by consecutive coating and solvent evaporation followed by final curing. Glass transition temperatures (Tg) of 89 °C (EEW-900) and 101 °C (EEW-500) were deduced by dynamic mechanical analysis (DMA). The lower Tg value was attributed to the higher EEW and a lower network density. Moreover, master curves along with Williams–Landel–Ferry and Prony series parameters were generated. By digital image correlation (DIC)-assisted tensile testing of single epoxy films at temperatures from 30 to 150 °C, a significant drop in tensile modulus from 2600 to 10 MPa and a rise in Poisson’s ratio from 0.35 to 0.47 was ascertained. The implemented finite element model (FEM) showed a good agreement with the experimental data.

Graphical Abstract