Development of Epoxy‐Based Adhesive Films Compatible With Oily Metal Surfaces and Investigation of Their Properties

ABSTRACT In this research, epoxy‐based adhesive films compatible with oily metal surfaces were developed and characterized. Because epoxy groups in their backbones are compatible with epoxy resins and long‐chain aliphatic groups can dissolve oils, epoxy soybean oil (ESO) and C12–C14 alcohol glycidyl ether (MGC) were added to reference adhesive at varying amounts. Seven adhesive film formulations, including a reference adhesive, were prepared to investigate the effects of additives on rheological, thermal, and tensile lap shear strength (TLSS) properties. The addition of ESO notably increased the gelation time at 120°C, whereas using MGC exhibited no significant impact on the gelation time. TGA analysis showed a decrease in the residue content of the cured films incorporating ESO and MGC. FTIR analysis further demonstrated that strong absorption band at 915 cm − 1 , attributed to the epoxide ring, was reduced after the curing process. TLSS testing was conducted by applying a reference adhesive film to both cleaned and uncleaned aluminum plates, and adhesive films containing ESO and MGC additives to uncleaned surfaces. Adding 4% ESO to reference formulation provided the same strength as the reference adhesive film applied to cleaned aluminum plates. The results demonstrated that films containing 4% ESO can be used without surface cleaning in applications.