Debabrata Chakraborty

Epoxy resin/poly(ethyl acrylate)—interpenetrating polymer networks: engineering properties and morphology

Interpenetrating polymer networks were prepared by the sequential mode of synthesis using an epoxy resin as the plastomer and poly(ethyl acrylate), PEA, as the elastomer components, respectively. Two types of IPNs; viz. full and semi, were prepared and characterized by measurements of tensile strength, elongation at break, modulus and toughness. Thermal properties were studied by differential scanning calorimetry and thermogravimetry. The morphological features were studied through scanning electron microscopy and polarized light microscopy. The effects of variation of the blend ratio on the above-mentioned properties were examined. Both semi and full IPNs showed a gradual decrease in modulus and tensile strength with consequent increases in elongation and toughness on increasing the proportion of the elastomeric component, PEA. The full IPNs were, however, characterized by higher modulus and tensile strength. The thermogravimetric results indicated that instead of a stepwise unzipping process of depolymerization as observed with PMMA, a CC bond scission occurred without formation of free radicals in the case of PEA. The calorimetric results showed one glass transition temperature Tg in between the Tg values of the plastomer and elastomer components suggesting extensive phase mixing. The morphology indicated a higher proportion of dissolved rubber particularly at the lower concentrations of PEA. Phase separated rubber domains being developed at higher concentrations also increased elongation at break since cavitation or crazing was promoted at the interfacial boundary. The elongation was limited to the extent of cavitation and therefore large increases in toughness were not found.