Cure kinetics of epoxy/chicken eggshell biowaste composites: Isothermal calorimetric and chemorheological analyses

Chicken eggshell (ES) is a biowaste powder comprising peptide functional groups and proteins, which give it potential to play the role of curing aid when added to the epoxy resin. In this work, pristine and terpolymer-modified ES (mES) were used in epoxy-based composites and their performance in network formation was compared with pristine calcium carbonate (CaCO3) and terpolymer-modified CaCO3 (mCaCO(3)) additives, via comprehensive isothermal calorimetric and chemorheological analyses. The mechanism and progression of the crosslinking of identical composites containing very low amount of additives were also discussed. Rheokinetic evaluations revealed that, despite the almost identical chemical structure of the ES and CaCO3, the former can more appropriately contribute to crosslinking reaction in the pristine form, since terpolymer modification causes a physical hindrance to its cure potential towards epoxy rings after surface modification. In the case of calorimetric studies, in contrast to nonisothermal cure kinetics, a more comprehensive image of the catalytic role of mES was identified in view of overall reaction order and apparent activation energy calculated for both types of systems.