Epoxy-silica hybrids

Epoxy-silica hybrids are well known for their abrasion resistance and low thermal expansion due to the presence of nanostructured bi-continuous domains. Most recently they have entered the market as anticorrosion coatings in the marine held, for yachts and for large metal vessels, such as oil tankers, and in particular for cargo or ballast tanks and on hulls (Figure 4.9). 

Figure 4.10 Transmission electron micrographs of (top) epoxy-silica hybrid (15% w/w Si02) and (bottom) the corresponding molybdenum-doped hybrid. (Reproduced from ref. 12, with permission.)... 

L. Mascia, L. Prezzi, G. D. Wilcox and M. Lavorgna, Molybdate doping of networks in epoxy-silica hybrids domain structuring and corrosion inhibition, Prog. Org. Coat., 2006, 56, 13. 

Figure 24.4 TEM micrographs of systems containing 15 wt% SiOi, both produced from a bisphenol-A epoxy resin grafted with an amine alkoxysilane-coupling agent (a) epoxy/silica hybrid (cocontinuous domains) and (b) epoxy/silica nanocomposite (particulate silica domains).

Additional constituents have been introduced to epoxy-silica hybrids to achieve specific properties. For instance, the incorporation of small amounts of a sUane-functionalized perfluoroether oligomer has been found to considerably reduce the surface energy of membranes. This has been attributed to the migration of the ftuoroligomer-derived species from the bulk to the surface, which continues even after curing, through a slow-release mechanism 14]. 

Figure 24.5 Comparison of linear expansion as function of temperature of an epoxy resin controi with an epoxy/silica nanocomposite and an epoxy/silica hybrid.

Figure 24.6 Comparison of room-temperature TH F absorption as a function ofimmersion timeof an epoxy resin control with epoxy/silica particulate nanocomposite and epoxy/silica hybrid (bicontinuous nanocomposite).

Prezzi, L and Mascia. L. (2005) Network density control in epoxy-silica hybrids by selective silane functionalization of precursors. Adv. Polym. Technol., 24, 13. 

An agreement with experimental results was obtained by taking into account the increased effective fraction of the filler, Veff, due to the glassy interphase of the bound epoxide layer and assuming a co-continuous morphology of the epoxy-silica hybrid network. Mechanical properties in dependence on the phase continuity are treated by parallel and series models for bicontinuous morphology and discontinuous phases, respectively. The equivalent box model (EBM) developed by Takayanagi (13) (eqs 2-5) and Davies model (14) (eq. 6) were used to compare the experimental data with the theory (9). 

Structure and morphology of the epoxy-silica hybrid systems is determined by (a) reaction mechanism of the sol-gel process in formation of the silica structure,... 

CardeU C, Delalieux F, Roumpopoulos K, Moropoulou A, Auger F, Van Grieken R (2003) Salt-induced decay in calcareous stone monuments and buildings in a marine environment in SW France. Constr Build Mater 17(3) 165-179. doi 10.1016/S0950-0618(02)00104-6 Cardiano P (2008) Hydrophobic properties of new epoxy-silica hybrids. J Appl Polym Sd 108(5) 3380-3387. doi 10.1002/app.27985... 

V lez, J.F., Procaccini, R.A., Aparicio, M., and Mosa, J. (2013) Epoxy-silica hybrid organic-inorganic electrolytes with a high Li-ion conductivity. Electrochim. Acta, 110,200-207. 

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