A deep knowledge of the behaviour of multi-component products for stone protection by an integrated analysis approach

The application of hydrophobic polymers to stone materials is an important treatment to preserve stone artefacts and protect cultural heritage from decay. To improve the characteristics and performance of water-repellent treatments, new solutions have been explored. In this research context, great attention has been paid to multi-component formulations that contain various monomers and copolymerise directly on stone. When they are obtained on inert rather than real substrates, such as stone, polymeric materials are often quite different in terms of their chemical and physical characteristics, polymerisation rate, and rheological properties. The stone's characteristics strongly influence its response to the application of conservation products; so different issues may be seen when applying the same treatment, depending on the interaction between the applied product and the stone support. Because of this, it is crucial to have the right tools to investigate how the substrate affects the monomers’ distribution of the applied mixtures and the resulting performance of the treatments. In this study, we followed an integrated approach based on the data collected by different analytical techniques (contact angle and colorimetric measurements, FT-IR analyses and ESEM-EDS analyses) to acquire a deeper knowledge of the behaviour of potential innovative water-repellents and their interaction with a stone support. This combined approach was used to evaluate the behaviour of methacrylate/vinyl-polysiloxane multi-component water-repellents applied on two calcareous stones displaying different microstructure and porosity: a compact limestone and a porous calcarenite.The results obtained show that the study of a multi-component mixture/substrate system by an integrated analytical approach allows one to assess the efficacy of new water-repellents and identify critical issues related to the nature of the support, providing useful information for the engineering of these chemical systems.

► Methacrylate/vinyl-polysiloxane protective products copolymerizing directly on stone.
► Chemical, physical and morphological integrated analyses.
► Monitoring of the physical surface parameters.
► Outcomes of the treatments depending on the system “multi-component mixture/substrate”.