Abstract. 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.Keywords : polymer composites, thermal properties, mechanical properties, morphology, moisture absorption eXPRESS Polymer Letters Vol.2, No.5 (2008) [339][340][341][342][343][344][345][346][347][348] Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2008.40 homogeneous hybrid thermoplastic modified epoxy with low fractions of thermoplastics [18]. It is reported that the incorporation of high performance thermoplastics into a thermoset resin system leads to significant improvements in mechanical properties [9,[19][20][21][22] [28][29][30][31][32]. Bismaleimides posses high crosslinking ability, high glass-transition temperature, high thermal ability, high char yield, excellent fire resistance, superior specific strength and specific modulus, and low water absorption. In continuation of our earlier studies, an attempt has been made in the present investigation to improve both toughness and thermo-mechanical properties of epoxy resin by incorporating hydroxyl terminated polyethersulfone (PES) and N,N′-bismaleimido-4,4′-diphenyl methane(BMI).
Materials and methodsEpoxy resin [diglycidyl ether of bisphenol A (DGEBA)] LY556 (epoxy equivalent 189 and viscosity 10 000 cP) and 4,4′-diaminodiphenylmethane (DDM) were obtained from Ciba-Geigy (India). N,N′-bismaleimido-4,4′-diphenyl methane was synthesized in our laboratory as per the reported procedure ( Figure 1) [33]. Hydroxyl terminated polyethersulfone was supplied by Jilin University, China was used as received. The chemical structures of materials used are presented in Figure 2.340 Rajasekaran et al. -eXPRESS Polymer Let...
