Atomistic modelling of the adsorption of epoxy and amine molecules on the surface of carbon fibres

Atomistic molecular modelling was used to investigate theoretical differences in adsorption behaviour of the two major components in an epoxy resin system. The model used quantum mechanical calculations to define charges and bond angles within adsorbate molecules, and a charge equilibrium algorithm to define carbon fibre surface charges. The carbon fibre surface model was constructed with reference to data provided by X-ray photoelectron spectroscopy. Modelling was undertaken using the 'Cerius" software of Molecular Simulations Ltd. Probe molecules were minimized onto the surface of the carbon fibre under the influence of the Dreiding 2.2.1 force field. Trends obtained from the modelled data were corroborated by independently derived inverse phase gas chromatography (i.g.c.)data. Minimization of components of the epoxy resin 922 onto the carbon fibre surface showed that the epoxy molecule was more strongly attracted to the carbon fibre surface than the amine hardener. Micromechanical testing provided evidence of an epoxy-rich interphase.