Design of Interpenetrating Networks for the Formation of Tough Epoxy Resins

Interpenetrating polymer networks (IPNs), in which macroscopically homogeneous mixtures are formed containing two distinct network-forming polymers, provide a route to producing mechanically superior thermoset materials.  Such materials can be useful in a wide variety of applications, including composites for wind energy, structural applications, and adhesives, among others. In this study, IPNs were prepared consisting of polydicyclopentadiene (polyDCPD), contributing enhanced toughness and impact strength, and an epoxy resin (the diglycidyl ether of bisphenol A cured with nadic methyl anhydride), contributing high tensile strength and modulus. The concurrent curing of the networks resulted in macroscopically phase separated blends. In situ Fourier transform infrared spectroscopy was used to explore the reaction kinetics in neat systems and diluted mixtures of epoxy resin and polyDCPD. A sequential curing protocol was developed, in which the polyDCPD was first cured in the presence of the epoxy resin components, followed by curing of the epoxy resin at an elevated temperature. These results provide the kinetic basis for future studies to prepare interpenetrating polymer networks which employ thermodynamic control of phase separation such as through the addition of compatibilizing molecules.