Synthesis and Characterisation of Organo-Modified Silica Nanostructured Films for the Water-Repellent Treatment of Historic Stone Buildings

Cristian Petcu,Ludmila Otilia Cinteză,Elvira Alexandrescu,Adriana Bălan,Maria Antonia Tănase

doi:10.3390/coatings10101010

Abstract

This study presents the facile sol-gel synthesis of nanostructured coatings for use in water-repellent treatment of travertine stone. The synthesized materials combine surface roughness characteristics with particular chemical compositions to give different hydrophobicity results. The influence of the silica particle coating precursor on the hydrophobicity of the polymeric film was investigated, and the octyl-modified silane was selected for further fabrication of the hybrid coatings. The water repellent properties, together with composition and structural properties of the silane-based hybrid material were measured on model glass surface. The coating with the best characteristics was subsequently deposited onto the travertine stone. The potential applicability of the nanostructured material was evaluated considering both the properties of the coating film and those of the travertine stone subjected to the treatment. The surface texture of the film, water repellent properties and uniformity were determined using scanning electron microscopy, atomic force microscopy, dynamic light scattering and contact angle measurements. The coating’s potential for use in stone conservation was evaluated by assessing its impact on the stone’s visual aspect. All the results obtained from the different types of analyses showed that the octyl-modified silica nanostructured material was highly hydrophobic and compatible both with the travertine stone and with the requirements for use on cultural heritage monuments.

Highlights

Despite the countless efforts made by the international community to preserve heritage monuments, even those built of stone are subject to the constant and inevitable processes of degradation.International monitoring programmes, especially in the last decade, proved the necessity of applying specific treatments for the preservation of these monuments, subjected to weathering, pollution, climate change and other aggressive factors [1].One of the most commonly used stones in historic monuments all over the world is travertine.This is a dense, finely crystalline limestone with various colours, from white to cream and pale tan.It usually has a fibrous or concentric structure and splintery fracture [2]
One of our aims was to avoid the use of fluorinated polymers, already widely applied in superhydrophobic industrial treatments [16], due to the concerns about the toxic air contaminants that result in thermal processing and the long-term impact of their release in various ecosystems [17]
Water repellent is one of the main properties exhibited by hydrophobic and superhydrophobic surfaces

Summary

Introduction

Despite the countless efforts made by the international community to preserve heritage monuments, even those built of stone are subject to the constant and inevitable processes of degradation.International monitoring programmes, especially in the last decade, proved the necessity of applying specific treatments for the preservation of these monuments, subjected to weathering, pollution, climate change and other aggressive factors [1].One of the most commonly used stones in historic monuments all over the world is travertine.This is a dense, finely crystalline limestone with various colours, from white to cream and pale tan.It usually has a fibrous or concentric structure and splintery fracture [2]. Despite the countless efforts made by the international community to preserve heritage monuments, even those built of stone are subject to the constant and inevitable processes of degradation. International monitoring programmes, especially in the last decade, proved the necessity of applying specific treatments for the preservation of these monuments, subjected to weathering, pollution, climate change and other aggressive factors [1]. One of the most commonly used stones in historic monuments all over the world is travertine. This is a dense, finely crystalline limestone with various colours, from white to cream and pale tan. It usually has a fibrous or concentric structure and splintery fracture [2].

Objectives

Methods

Results

Conclusion