Polymeric dispersions for the protection of limestone: application on noto and comiso stone

Abstract

ABSTRACT: Architectural heritage made of limestone faces a lot of threats due to the presence of water intrusions from various sources. This problem encouraged the development of hydrophobic polymeric dispersions for the protection of stone objects. In the following study, Noto and Comiso stone samples were selected and treated with three commercial protective polymeric dispersions of different chemical composition. Untreated samples were characterized by optical microscopy, porosimetry, XRD and XRF. An extensive characterization of the treated samples was performed in order to evaluate the changes in the stone properties upon treatment with the dispersions. According to UNI EN recommendations, several tests were performed in order to evaluate developed hydrophobic effects and chromatic changes. SEM-EDX was used to study the elemental composition of the surface and to observe changes in its morphology. Reflection FT-IR spectroscopy and ss-NMR gave insight about the polymer-substrate interactions. From liquid water absorption measurement, on both Noto and Comiso stone, it was observed that Fluoline HY and Wacker 290 significantly reduced samples’ ability to absorb liquid water, while Silo 111 did not show any significant impact. Reduction of water vapour permeability was observed in all cases, except on Comiso stone samples treated with the minimum amount of Wacker 290, which seems to have had the best performance in avoiding complete pore clogging. Fluoline HY, when the minimum amount was applied, gives also a low pores’ filling while Silo 111 seems to obstruct to some extent the accessible porosity. SEM-EDX analysis confirmed the presence of polymer on the stone surface in all cases.