In Situ Analysis of the Relationship between Cure Kinetics and the Mechanical Modulus of an Epoxy Resin

Abstract

The cure kinetics of epoxy cured with an amine hardener is investigated using a combination of light scattering techniques. Concurrent Raman and Brillouin scattering are used to monitor the formation of epoxy networks over time in terms of both the structural connectivity of the network and the evolution of chemical bonding configurations. The relationship between the elastic properties of the network and the degree of cure was found to depend on the cure temperature and the resin–hardener stoichiometry. A numerical model was created to determine the degree of cure and elastic modulus as a function of time and cure conditions. Accordingly, the modulus of the epoxy comprises two contributions: one directly related to the concentration of covalent bonds that form and another one due to nonbonding interactions that arise as the network relaxes into an optimally packed configuration.