Synthesis of Halogen-Containing Methylenedianiline Derivatives as Curing Agents for Epoxy Resins and Evaluation of Mechanical Properties of Their Carbon-Fiber-Reinforced Polymers

Owing to their superior mechanical performance, strong adhesion, thermal resistance, and insulating properties, epoxy resins are commonly employed as protective coatings, electronic encapsulants, adhesives, and matrices in composites. The selection of the epoxy system components—the base resin and curing agent—along with the chosen curing protocol, directly determines the properties of the final cross-linked polymer. This study compares the influence of halogen substituents in 4,4′-methylenebis(2,6-diethylaniline) (MDEA), 4,4′-methylenebis(3-chloro-2,6-diethylaniline) (MCDEA) and 4,4′-methylenebis(3-bromo-2,6-diethylaniline) (MBDEA). The results of mechanical tests on plastics and composites demonstrated an increase in the strength properties and elastic modulus of the matrix, improved adhesive interactions with carbon fiber, and showed a reduction in moisture saturation across the series MDEA → MCDEA → MBDEA. Notably, the improvement in properties exceeded the increase in the density of the compositions, indicating an enhancement in the specific characteristics of the matrix.