Epoxy resins are ubiquitously encountered in industrial applications as in adhesives and composites. The properties of epoxy-amine networlcs are directly impacted by the presence of metal (bydr-oxidized) surfaces, leading to a modificati on of their glass transition temperature T 8 • We propose here an innovative experimental approach, investigating the interaction of DET A amine and DGEBA epoxy with Al and Cu powder substrates (partially (hydr)oxidized). We explored for the first tiine the formation of the amine-metal interphase by in situ mixing calorimetry to evaluate the energetics of interaction. While DGEBA interacted only sl ightly with Al-based surface, the reaction with OETA was associated with a high exothermic enthalpy of reaction. The enhancing role of surfaoe hydroxylation was also evidenced by comparing boehmited Al to a simply oxidired counterpart. An even larger exothermic effect was measured with copper, which was related to the high chelating power of Cu compared to Al. The possible underlying mechanism of amine-metal interphase formation was discussed with a generalized schematic.
Among thermosetting polymers, epoxy resins are major components of adhesives, sealants, paints and composites. Polymerization is often achieved by reaction of epoxy monomers like DGEBA with amine hardeners such as DETA. Previous works showed that polyamines interact with metal (hydr/oxide) substrates leading to the formation of an interphase involving the chelation of surface metal ions. In this work, we further explored the interaction between DETA and aluminum (hydr)oxide, denoted Al, via a combined experimental and modeling approach. We inspected in depth by DSC the modifications of glass transition temperature T g and change in heat capacity ΔC p after curing, allowing us quantifying the impact of Al amount on DGEBA/DETA degree of cure α. A new parameter, the "percentage of inhibition of cure" denoted α, was defined reaching up to ~4 % in our experimental conditions. In parallel, in situ mixing calorimetry confirmed the exothermic character of DETA interaction with Al with various degrees of division. DFT calculations were carried out to examine DETA/Al 3+ chelates. Among plausible chelate configurations, one was associated with a lower conformational energy and shorted Al-N bond lengths, suggesting greater stability. Calculated and experimental Raman spectra were additionally investigated, allowing us to discuss further about the DETA/Al 3+ chelates at play.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.