Abstract
Epoxy-amine/aluminum chemical systems or sandwich structures with and without interphase formation are prepared using two different curing cycles and are characterized with dielectric spectroscopy. The sample without interphase formation is obtained when the reaction between epoxy and amine groups is favored, which occurs at high temperature. The interphase formation results from the reaction between the amine group and aluminum surface at room temperature. Dielectric spectra are fitted using the Set Inversion Via Interval Analysis (SIVIA) algorithm applied to DiElectric spectroscopy algorithm (SADE) developed using the method of intervals analysis. A new approach is implemented using a sum of Debye relaxations to optimize and guarantee the fitting. The results achieved show a distribution of relaxation times, which always take place at the same time as demonstrated. In this study, five Debye relaxations were found which fit the β-relaxation with our model. Finally, we showed that the more intensive of our five β -relaxations follows the Arrhenius law.
Highlights
Epoxy-amine/aluminum bonded assemblies present an interesting alternative to other techniques used in industry, such as riveting, bolting, welding, etc.In this work, an epoxy-amine prepolymer is applied to an aluminum substrate and cured such as to obtain, or not, an interphase, as reported in previous works [1,2]
There are many relaxations, two of them will be presented in the following :
For temperatures T < Tamb in the case of epoxy-amine the relaxation observed is the β-relaxation
Summary
Epoxy-amine/aluminum bonded assemblies present an interesting alternative to other techniques used in industry, such as riveting, bolting, welding, etc. When an epoxy-amine mixture is deposited on the surface of aluminum, a transition zone, more or less thick, with different properties from the bulk materials is formed, and called an interphase [3]. It presumably originates from dissolution of the native oxide layer of aluminum at the surface of the metal substrate which results in the formation of organometallic complexes which are going to form the interphase in uncrosslinked prepolymer causing changes in physical, chemical and mechanical properties of the polymer [4]. Dielectric spectroscopy is used to characterize the behavior of epoxy-amine/aluminum bonded assemblies This characterization gives us information about relaxations of dipoles and charges carriers of the material and the molecular dynamics versus the frequency. This sum of Debye relaxations gives information about collection of dipoles and about distribution of relaxations
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