Epoxy-silica polymers as stone conservation materials

The reaction of the epoxy derivatives 2-(3,4-epoxycyclohexyl)ethyl-trimethoxysilane (ECET) and (3-glycidyloxypropyl)methyldiethoxysilane (GLYMS) with the primary amine (3-aminopropyl)triethoxysilane (ATS) leads to solids that have been investigated by means of TG-DTA, FT-Raman and FT-IR spectroscopy. Solution 13C NMR and solid state FT-Raman spectra show that the oxirane ring of ECET is not involved in the epoxy-amine addition. The structure of the resulting materials consists of a siloxane network with pendant epoxycyclohexyl groups. On the contrary, when GLYMS is allowed to react with ATS, the polymeric network develops either on the organic as on the inorganic side so that the resulting materials may be viewed as silica-epoxy hybrids with organic polymer chains covalently linked to inorganic domains. Porosity, water absorption properties and dynamic contact angle measurements were used to preliminarily evaluate the efficacy of the above materials as conservation products.