Nanocomposites and nanomaterials
Epoxy-silica composite materials by sol-gel: formation and properties
Sayfutdinova M.V., Lyga R.I., Mikhal’chuk V.M.
Donetsk national university. Shchorsa, 17a, Donetsk-83001, Ukraine. 
E-mail: sayfutdinovam@list.ru

Recently, a significant amount of research is directed to the study of the effect of inorganic nanoparticles, in particular, silica, on the properties of epoxy composite materials [1]. The sol-gel preparation technology allows to form filler particles in situ and to mix the components of the system at the nanoscale. It results in a high homogeneity of the particles distribution in the organic matrix and improves the characteristics of the composites. In general, the sol-gel method is carried out by hydrolytic polycondensation of the silicon alkoxide using different amounts of hydrolytic water. The aim of this work was the development of preparation method of amine cured epoxy-silica composites by sol-gel method without the preliminary formation of silica-sol particles and without using of solvents, and studying of the morphology of their structure and the influence of silica-based filler on the thermal stability of epoxy polymers.
The amine cured silica composites based on epoxy resins of various viscosities and tetraethoxysilane (TEOS) were obtained via sol-gel method. Silica in an amount of 0.5 to 10 wt. % was formed in situ by hydrolytic polycondensation of tetraethoxysilane. In this case, TEOS and the cycloaliphatic polyamine is introduced directly into the epoxy resin. X-ray phase analysis of obtained composites was showed that crystallization does not occur during the formation of the inorganic constituent of the composites.
In general, the inorganic filler exerts the plasticizing effect on the polymer matrix, the glass transition temperature of the composites decreases. It was established by TEM that the inorganic constituent is structured even before the formation of the epoxy matrix. After burning out the organic component of the composites, the sponge-like silica airgel remains. With increasing filler concentration, the airgel density increases. Thermogravimetric analysis of composites showed that the introduction of the silica filler into the polymer matrix raises the temperature of begin of degradation main stage on 10-25 ° C, and the temperature of end of destruction main stage on 20–37 °С.

1.	Ahmad F., Al-Sagheer. Novel epoxy-silica nano-composites using epoxy modified silica hyper-branched structure // Progress in Organic Coatings.-2015.-80.-P. 65-70.