Research of the Intramolecular Interactions and Structure in Epoxyamine Composites with Dispersed Oxides

Abstract

With the help of the software package HyprChem, using a method of quantum-chemical modeling, research into intermolecular interactions between epoxyamine grid and oxides of different chemical nature Al2O3, Fe2O3, TiO2, СаО was carried out. To take into account hydroxyl-hydrate surface layer of oxides, molecular complexes of the fragment of epoxyamine grid and hydroxides of metals Al(OH)3, Fe(OH)3, Ti(OH)4, Ca(OH)2 were used as models. As a result of modeling, it was established that Ca(OH)2 molecule forms strong intermolecular bonds and has the greatest influence on the spatial conformation of the epoxyamine fragment. It was shown that a calcium atom is oriented to π-electron cloud of the benzene ring with formation of donor-acceptor bond, and OH-groups form hydrogen bonds with OH-groups of the residue of a molecule of epoxy oligomer in the grid. The studied intermolecular interactions of epoxyamine grid and hydroxides of amphoteric metals Al(OH)3, Fe(OH)3, Ti(OH)4 indicate the formation of low-energy inductive and dipole-dipole (orientation) bonds. It was established that existence of amphoteric hydroxides does not cause a change of the spatial conformation of the grid's fragment. It was shown that the ability of hydroxides of metals to affect the spatial conformation of a fragment of the epoxyamine grid increases in the series: Ti(OH)3<Al(OH)3<Fe(OH)3<Ca(OH)2. The resulting series coincides with the series, in which basic properties of active Branstad centers (OH-groups) with the central elements Ti4+<Al3+<Fe3+<Ca2+ increase (acidic properties decrease). The influence of the oxide filler on the structure and spatial conformation of epoxyamine grid increases with an increase of basicity (alkalinity) of an oxide. Resistance of composites to aqueous aggressive media depends on the surface acidic-basic properties, dispersion and package density of fillers' particles in the polymer matrix. When adding strongly basic calcite oxide (CL), chemical resistance of composites decreases by 5 times. In this case, composites with non-homogeneous structure and non-uniform distribution of compacted areas are formed. It was found that when adding amphoteric rutile oxides (RT), alumina (AL) and hematite (HM), the main factors that affect chemical resistance of filled composites include dispersion and package density of fillers' particles. The calculated parameter a of composites, which describes package density of the filler in the polymer matrix, increases in the series of fillers HM<RT<AL. This series coincides with the series, in which resistance of filled composites in all aggressive media decreases. At an increase in package density of a filler, probability of pegridration of aggressive medium into the material decreases, which is associated with extension of the diffusion path