Design and development of hybrid coatings for conservation and restoration of cultural heritage

Geopolymers are inorganic materials that form long-range, covalently bonded, networks; they are materials similar to ceramics, whose components are mainly aluminum and silicates Any inorganic source of silica and alumina, dissolved in the alkaline solution, acts as a precursor of geopolymers and therefore lends itself to geopolymerization. The type of clay most commonly used in the synthesis of geopolymers is based on kaolinite. A green method to implement these properties consists of incorporation of coupling silane agents5 and organic fillers during the geopolymerization process. The methods of functionalization of the geopolymers shown in this work are: (i) the treatment of the geopolymeric surface, post-drying, through the application of the sol-gel directly on the monolith, for a modification of the surface properties; (ii) the pretreatment of the geopolymeric mixture, through the addition of the alkoxysilane which can induce a homogeneous consolidation of the molecular structure, implementing the properties of the entire monolith. In this work we show the design and development of hybrid coating sol-gel formulations to apply on geopolymer surface to improve characteristics such as mechanical strength6, chemical inertness, heat resistance and porosity for possible use in the restoration and conservation of cultural heritage. The surface treatment is carried out using different alkoxysilanes7, which differ according to the length of the hydrocarbon chain and the presence of halogen atoms or epoxy groups. Hydrophobicity and antifouling tests were performed on these formulations.