Enhancing Impact Strength and Compatibility in Epoxy/ EVA Blends: Effects of EVA Functionality and Compatibilizers on Phase Behavior, Mechanical Properties, and Thermal Properties

Abstract

This research focuses on toughening epoxy (EP) resins by blending with ethylene vinyl acetate (EVA) copolymer, addressing their inherent immiscibility through chemical modification. EVA was partially hydrolyzed (hEVA) to introduce hydroxyl groups and subsequently grafted with (3‐glycidyloxypropyl) trimethoxysilane (GPTMS) to create silane‐functionalized derivatives (gEVA and hgEVA). Materials included Diglycidyl ether of bisphenol A (DGEBA) epoxy, Jeffamine D230 curing agent, neopentyl glycol diglycidyl ether (NGDE) reactive diluent, Decylamine (DA) co‐curing agent, and EVA (19% vinyl acetate). Blends were prepared via melt‐mixing at 150°C, followed by co‐curing. Characterization methods such as scanning electron microscopy (SEM), optical microscopy, and Fourier transform infrared (FTIR) were employed to analyze morphology, phase behavior, and chemical interactions. SEM revealed finer dispersions with modified EVAs, indicating enhanced interfacial adhesion. FTIR confirmed successful modifications and suggested new bond formations between EP and modified EVA. The study systematically investigated EP/EVA blends at varying compositions (2–10 wt% EVA, 5 wt% modified EVA) and characterized their thermal properties and mechanical performance (tensile testing). Notably, the EP/hgEVA blend demonstrated a significant increase in impact strength (~100%) while largely retaining EP's flexural and tensile strength, highlighting the effectiveness of the compatibilization strategy for advanced coating applications.