Effects of Iron and Iron Oxide Nanoparticles on the Curing Reaction Kinetics of an Epoxy Composite under Isothermal Conditions

The effects of metallic iron (Fe) and iron oxide (FeOx) nanoparticles on the curing kinetics of a filled composite based on ED-20 epoxy resin and the high-temperature amine curing agent metaphenylenediamine was studied by differential scanning calorimetry (DSC). The kinetic analysis of the crosslinking reaction was performed in the isothermal mode at temperatures from 70 to 120°C in 5°C increments. Isothermal curing below 110°C does not lead to complete crosslinking. This is hindered by vitrification of the forming three-dimensional polymer network and the ensuing conformational restrictions for the interaction of reactive groups. The crosslinking reaction kinetics was analyzed using an autocatalytic model. In the temperature range of 95–120°C, the activation energy of the reaction is 69 kJ/mol for both the ED-20 resin itself and its composites with nanoparticles. However, at lower temperatures of 80–95°C, the activation energy of the crosslinking reaction for the composites decreases by an order of magnitude. This indicates that Fe and FeOx nanoparticles produce a catalytic effect on the epoxy resin crosslinking reaction in this temperature range.