The Influence of Nanoreinforcement Inclusion on the Cure Kinetics of Epoxy Resin: Analysis Through Different Models

Abstract

Epoxy resin has become a cornerstone in the fabrication of high-performance composite materials, with the quality of these products relying heavily on the curing process. The use of nanoparticles as reinforcements in composite materials is still under study. In particular, the inclusion of these nanoparticles can significantly impact the cure kinetics of epoxy resin. Our study investigates this process through rheometric measurements. We meticulously examined five distinct samples: one of pure epoxy, two with a concentration of 2 wt.% of two types of organo-modified clay particles (C30 and C93), and two others with 0.25 and 0.5 wt.% of carbon nanotubes (CNT). Characterization was conducted at three temperatures—50°C, 75°C, and 100°C—and we applied three analytical models to understand the cure kinetics. The most compelling insights arose from a model based on nonequilibrium thermodynamic fluctuation theory, demonstrating its reliability. Also, it was found that the activation energy (Eact) of the curing process notably decreases with the inclusion of CNT, while the effect of clay varies depending on the type of organic modifier. Furthermore, we employed small-angle x-ray scattering (SAXS) measurements to evaluate the compatibility between the nanoparticles and the epoxy in the cured samples. Thus, the C30 clay demonstrated the most significant increase in interlaminar distance. Moreover, optical microscopy showed that the resin can also be effectively reinforced with carbon fiber, as the resin shows excellent wetting properties on the carbon fiber strands.