Effect of polyethersulfone and N,N′-bismaleimido-4,4′-diphenyl methane on the mechanical and thermal properties of epoxy systems

In order to improve thermo mechanical properties of cured epoxy resin, hydroxyl terminated polyethersulfone ( PES) and N,N'-bismaleimido-4,4'-diphenyl methane (BMI) were incorporated to diglycidyl ether of bisphenol A ( DGEBA) type epoxy resin and cured with diaminiodiphenylmethane (DDM). The resulting hybrid matrices, in the form of castings, were characterized for their mechanical properties like tensile, flexural and impact strength. Differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis of the matrices were also performed to determine the glass transition temperature and thermal stability of the matrix systems. The results obtained from mechanical and thermal studies indicated that the incorporation of polyethersulfone into epoxy resin improved the toughness and thermal stability of the systems. This is attributed to the formation of interpenetration polymer networks (IPNs) composed of the epoxy network and the linear PES. The incorporation of BMI into polyethersulfone modified epoxy systems increased thermal stability, glass transition temperature, tensile and flexural properties and decreased the impact strength. Scanning electron microscopy studies of polyethersulfone modified epoxy and BMI incorporated polyethersulfone modified epoxy systems exhibit homogeneous morphology confirming efficient chemical interaction and formation of intercrosslinked network structure.