In Situ Vibrational Probes of Epoxy Gelation

Abstract

This paper presents an efficient way to measure the curing kinetics and gel point, α gel , in epoxy resins from one single experiment. The epoxy curing reaction is herein monitored using in situ and time-resolved near-infrared absorption spectroscopy (NIR). The curing profiles over different isothermal conditions are in good agreement with DSC. Furthermore, the increase of the NIR absorption bands of aromatic rings (unreactive throughout curing) probe the cure shrinkage, as more and more aromatic rings are localized within the fixed sample volume. Therefore, the gel point is determined using the onset of the aromatic absorption increase. The results are in good agreement with the theoretical gel point, as well as DMA results. This innovative approach enables gelation measurements on epoxy neat resins and film composites with an easy-to-perform, accurate, robust, and versatile method.

Molecular Events for an Epoxy–Amine System at a Copper Interface

“…Epoxy resins are a promising adhesive material for transportation systems such as airplanes and automobiles thanks to their strong adhesive capability, lighter weight, and greater stiffness. − In general, a base resin and a curing agent, which are generally epoxy and amine compounds, respectively, are mixed to promote their cross-linking reaction. This leads to the formation of a three-dimensional network, which plays important roles in the modulus, thermal expansion, fracture behavior, and adhesive properties. − Because the adhesive material is coated on the solid surface, it is vitally important that a better understanding of the molecular picture of the performance and durability of the adhesion technology at the interface is obtained. However, the details of the interfacial chemical reaction can be experimentally difficult to understand because the thermodynamics and kinetics at the interface are not the same as those in the corresponding bulk system .…”