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Abstract
The present work investigates the effect on the morphology, fracture performances, and tensile properties of an epoxy polymer when modified with various percentages of a thermoplastic-polymeric toughener. The thermoplastic toughener was a poly(ether sulfone) copolymer with reactive end-groups. It was initially soluble in the epoxy-resin/hardener mixture but phase separated during the curing of the epoxy resin. After the epoxy had cured, the thermoplastic toughener, when present at relatively low concentrations, possessed a spherical-particulate morphology in an epoxy-rich continuous phase. However, as the weight percentage of the thermoplastic was increased the morphology changed to a co-continuous microstructure, and then to a phase-inverted microstructure of epoxy spherical particles in a thermoplastic-rich continuous phase. The Young's modulus and 0.2% proof stress of the epoxy polymer were relatively unaffected by the addition of the thermoplastic, whilst the ultimate tensile strength increased with increasing thermoplastic content. The fracture toughness and fracture energy of the formulations were found to increase steadily with increasing thermoplastic content. This increase was not, however, linked to the observed changes in morphology, but simply to the weight-percentage of the thermoplastic toughener added to the formulation.
ACKNOWLEDGMENTS
The authors would like to thank the Engineering and Physical Sciences Research Council and Cytec Engineered Materials for funding the project, and the Royal Society for the Mercer Award which provided funding for some of the equipment used.
Notes
One of a Collection of papers honoring David A. Dillard, the recepient in February 2010 of The Adhesion Society Award for Excellence in Adhesion Science, Sponsored by 3M.