Preparation, characterization, thermo-mechanical, and barrier properties of exfoliated thermoplastic toughened epoxy clay ternary nanocomposites

Ternary nanocomposites are prepared by blending hydroxyl-terminated poly ether ether ketone having pendant methyl groups (PEEKMOH) with epoxy resin along with Nanolin DK1, followed by curing with 4,4'-diamino diphenyl sulphone. Differential scanning calorimetry shows a two-stage cure behavior indicating the catalytic effect of the primary amine and proton, which are generated by the dissociation of organic modifier. Tensile and flexural moduli are increased while tensile strength and glass transition temperature are decreased with increase in clay concentration. Fracture toughness and strain at break are increased by 59 and 62%, respectively, with 1 phr clay loading. Transition electron microscopy and X-ray diffraction (XRD) analysis reveal exfoliated morphology for the nanocomposites. Scanning electron micrographs show a decrease in both, domain size as well as inter domain distance of the thermoplastic phase with the addition of clay, indicating the occurrence of gelation before phase separation. Analysis of the fracture surface reveals crack path deflection and ductile fracture behavior, confirming that toughness has been improved with the addition of clay and PEEKMOH. Coefficient of thermal expansion (CTE) of the nanocomposites is decreased up to 3 phr clay loading. Oxygen gas permeability is compared with Bharadwaj's and Neilson's models. A marginal improvement in thermal stability is observed with the addition of clay. Copyright (C) 2009 John Wiley & Sons, Ltd.