“Influence of epoxy-amine/metal interphase formation on adherence in painted and glued systems : an experimental and numerical approach “
Host structure : the PhD student will work between two laboratories. The CIRIMAT Carnot Institute and the Institute Charles Gerhardt Montpellier (ICGM), Institute for Molecular Chemistry and Material Sciences
Application deadline : June 15, 2020
Duration : 3 years (01/10/2020 to 30/09/2023)
Epoxy resins represent a major family of thermosetting polymer precursors. They are encountered in various strategic industrial sectors, such as ground transportation and aeronautics, building and construction, sports and leisure. They are typically used as adhesives and sealants, coatings (e.g. paints, primers…) and composite matrices. They became commercially available since 1946 and were then extensively studied and used since the 1970s. Epoxy resins are often polymerized with amine hardeners, leading to epoxy networks. Independently of the application, the latter always involve interfaces: between fibers or fillers and the epoxy-amine matrix in composites, or between a (metal) substrate and epoxy-amine coatings or adhesives. Such 2D interfaces in 3D multimaterials can be considered as boundaries between two spatial regions occupied by different components. However, at a microscopic scale, these interfaces should more accurately be considered as extended tri-dimensional domains corresponding to so-called “interphases”, which may exhibit physical and/or chemical property gradients.
The properties of epoxy-amine networks are directly impacted by the presence of metal (hydroxidized) surfaces, leading to a modification of their glass transition temperature T g . We propose here an innovative experimental approach, investigating the interaction of various amine and epoxy monomers with metal substrates (partially (hydr)oxidized). We will explore the formation of the amine-metal interphase by in situ mixing calorimetry to evaluate the energetics of interaction. It was already shown that the epoxy monomer DGEBA interact only slightly with Al-based surface, whereas the reaction with DETA amine was associated with a high exothermic enthalpy of reaction. The possible underlying mechanism of amine-metal interphase formation will be discussed using molecular modelisation.
The main goal of this thesis is the interphases characterisation in order to link the interphase properties and the measured practical adhesion. For this experimental part, epoxide-amine/metal bonded joints will be chosen as model systems. Taking into account the practical adhesion reviews and articles, the three points flexure test (ISO 14679-1997) will be chosen as it guarantees an interfacial failure and the failure initiation measurement (instead of mixture of initiation and propagation mixture measurement). The interphases characterisation will be substantial. Moreover, except mixing calorymetry and Raman spectroscopy (having a confocal microscope) all the other techniques will be post-mortem (FTIR, DSC, . . . ).
Let us notice that all these techniques cooperate to reach better results. The DSC will give thermal characteristics whereas Raman and FTIR will chemically characterise the interphases.
All these techniques promise to characterise the formed interphase, and explain the practical adhesion results from the three points flexure test.
In parallel, a theoretical approach will be developed using DFT calculations. By considering clusters constituted (metals and amine/epoxyde groups), it will be possible to determine the energy for interactions between metals and organic parts, preferential configurations for amines and epoxyde groups and the prediction of Raman and infra-red spectra. Alle the theoretical results will be validated by the experimental data. The aim of the complementary methodology will allow us to better capture the behaviour of the interphases, by identifying the most probable reactive/intermediary species and in fine the behavior of multimaterials as a function of the epoxyde/amine and metals couples.
The PhD student will work in a «Carnot Institute », between two laboratories. The CIRIMAT Carnot Institute was created in 1999: this multidisciplinary unit gathers chemists, physicists, crystallographers, metallurgists and polymerists, therefore leading research projects expanding from the conception of materials to the study of their behaviour in use. Several steps are investigated: elaboration, characterization, modelling, as well as optimization of the properties and durability of the materials, and multi-scale approaches in view of industrial development. The CIRIMAT deals with a variety of research themes (both fundamental and applied), and is strongly oriented towards industrial needs, especially via regional, national and European research programs.
The Institute Charles Gerhardt Montpellier (ICGM), Institute for Molecular Chemistry and Material Sciences, is a Joint Research Unit (UMR 5253) created in January 2007 and supported by the Centre National de la Recherche Scientifique (CNRS), Université de Montpellier (UM) and Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM).
The ICGM is a multidisciplinary laboratory working in the fields of Energy, Environment and Health. Organized in three scientific departments, it represents 240 permanent staff and over 200 non-permanent staff (including doctoral students, post-doctoral students, and visiting/guest researchers). The team “Aggregates, Interfaces and Materials for Energy” (AIME) associates competence in innovative synthesis routes to hierarchical materials with tailored architecture and in surface reactivity and the chemistry of interfaces, with complementary theoretical and experimental approaches applied to energy storage and conversion and environmental remediation processes. The perspectives of the research are two-fold: elaboration of original materials enabling emerging energy technologies and the study of the interfacial properties and mechanisms governing exchange of energy and matter at various interfaces.
The candidate must have strong background and skills in polymers.
Knowledge in modelling (Density Functional Theory) is not mandatory but will be appreciated as well as the ability to fit in a multi-disciplinary team.
Term and salary
This PhD position is for 3 years (01/10/2020 to 30/09/2023) and the salary (gross) will be 1900 euros for 1 month.
Please send full CV including research interests and 2 references with contact information to Maëlenn AUFRAY and Fabrice SALLES, before June, the 15th. Then, job interviews will be organized by visio-conference.