Semi‐conductive Polyethersulfone/Epoxy Coatings with High Heat Resistance and Tensile Shear Strength

ABSTRACT Epoxy resin‐based polymer coatings characterized by high heat resistance and shear strength serve as critical adhesive materials in high‐end power equipment. In particular, semiconductive variants of such coatings can effectively suppress the nonlinear variation of insulation resistance in DC voltage proportional standard devices, thereby enhancing measurement accuracy. However, as the DC voltage level increases, the operational conditions under extreme temperatures impose more demanding requirements on the heat resistance and tensile shear strength of semiconductive polymer coatings. Currently, there remains a lack of effective methods to enhance the tensile shear strength of such high‐heat‐resistant resin‐based polymer coatings. To address these challenges, this study proposes a multifaceted modification strategy. By constructing a rigid molecular backbone, optimizing the ratio of rigid to flexible segments within the resin network, and incorporating a polyethersulfone (PES) toughening agent to promote plastic deformation of the resin matrix, the glass transition temperature and tensile shear strength of the coating were increased to 451.15 K and 14 MPa, respectively. Furthermore, the addition of 0.5 wt.% carboxyl‐functionalized multi‐walled carbon nanotubes (MWCNTs) as conductive filler reduced the absolute value of the minimum resistance–voltage proportionality coefficient by 73%, indicating a significant suppression of the nonlinear insulation resistance effect.