Benoît Minisini and Alexander Mavromaras will give an invited talk at the 2018 Surfair Congress 'Technologies for Environmental Compliance and Sustainability' held in Biarritz, France May 20-22, 2018. Surfair congress is the world’s leading biennial congress on Surface Finishing in the Aeronautics and Aerospace Industries since 1970. The International Congress is held every other year and brings together an international audience of decision-makers and experts from over 20 countries.
Our SurFair presentation summarizes recent R&D work by the Materials Design, Inc. team under the guidance of our polymer materials expert, Dave Rigby. The talk is entitled 'Computational Studies of Adhesion Between Crosslinked Epoxy and Hydroxylated Substrates'.
Here is the abstract:
Computational Studies of Adhesion Between Crosslinked Epoxy and Hydroxylated Substrates
B. Minisini, A. Mavromaras, and D. Rigby
Materials Design s.a.r.l., 42, avenue Verdier, 92120 Montrouge, France
Adhesive bonding between crosslinked thermosetting resins and inorganic or metallic substrates is of critical importance in a variety of materials applications including fiber or particle reinforced composites and bonding of metal parts used in the aerospace industry. In the simpler cases, bonding between the organic and inorganic or metal components occurs via van der Waals dispersive and electrostatic interactions. However, frequently, additional primer compounds are introduced to form covalent chemical bonds between the major system components.
We have recently used the MedeA simulation environment to conduct a series of investigations of the properties of crosslinked thermosets, including studies of the effect of resin architecture on small strain elastic constants of amine-cured epoxies, and gelation studies in epoxy and polyester systems (1), which show good quantitative agreement with available experimental data. These studies have been extended to include interfaces with a solid substrate which focused on model adhesive type systems in which crosslinked epoxy interacts with a model silica substrate. Two types of systems were considered, with the first containing only crosslinked epoxy and silica, and the second containing in addition the commonly-used primer gamma-aminopropyltriethoxysilane in which the ethoxysilane moieties have been pre reacted with the hydroxylated silica substrate prior to performing the amine-based crosslinking with the epoxy resin and curing agent. Following the model building, the epoxy-silica interface systems are typically equilibrated using the MedeA-LAMMPS simulation program (2, 3) before being to subjected to structural analysis to elucidate the nature of packing at the interface, accompanied by mechanical property calculation to compare and contrast the behavior of the systems when subjected to small deformations.
As a component of the most recent studies we have also performed refinement of earlier forcefield parameters for crystalline silica, which significantly improves the accuracy of predictions of properties of the bulk material. In this presentation, we will discuss the forcefield refinement work and will illustrate its application to a study of the effect of surface hydroxyl content on small strain elastic constants of model SiO2-epoxy materials. Finally, we will conclude with a discussion of analogous calculations on hydroxylated alumina surfaces such as those encountered in bonding of structural materials used in aerospace applications.
1. D. Rigby, C.M. Freeman, P.W. Saxe and B. Leblanc, Computational Prediction of Mechanical Properties of Glassy Polymer Blends and Thermosets, Proceedings of the 143rd Annual TMS Meeting, San Diego, CA, Feb 16-20, 2014.
3. S. Plimpton, Fast Parallel Algorithms for Short-Range Molecular Dynamics, J Comp Phys, 117, 1-19 (1995); http://LAMMPS.sandia.gov