Design, synthesis and characterization of hybrid coatings suitable for geopolymeric-based supports for the 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 aluminium andsilicates. Any inorganic source of silica and alumina, dissolved in the alkaline solution, acts asa precursor of geopolymers. The type of clays most commonly used in the synthesis ofgeopolymers is based on kaolinite. The present work concerns the modification of thegeopolymer at the chemical and nanostructural level, through the design and development ofhybrid coating sol-gel formulations to improve characteristics such as mechanical strength,chemical inertness, heat resistance and porosity for possible use in the restoration andconservation of cultural heritage. The methods of functionalization of the geopolymers hereshown are: (i) the treatment of the geopolymeric surface, post-drying, through the applicationof the sol-gel directly on the monolith, for a modification of the surface properties; (ii) thepretreatment of the geopolymeric mixture, through the addition of the alkoxysilane which caninduce a homogeneous consolidation of the molecular structure, implementing the properties ofthe entire monolith. The employed alkoxysilanes differ according to the length of thehydrocarbon chain and the presence of halogen atoms. Hydrophobicity tests were performed onthese formulations.