Pickering Emulsions Based on Wax and Halloysite Nanotubes: An Ecofriendly Protocol for the Treatment of Archeological Woods.

Lorenzo Lisuzzo,Stefano Sacanna,Giuseppe Cavallaro,Giuseppe Lazzara,Theodore Hueckel

doi:10.1021/acsami.0c20443

Lorenzo Lisuzzo, Stefano Sacanna + Show 3 more

Open Access

https://doi.org/10.1021/acsami.0c20443

Copy DOI

Abstract

A novel green protocol for the consolidation and protection of waterlogged archeological woods with wax microparticles has been designed. First, we focused on the development of halloysite nanotubes (HNTs) based Pickering emulsions using wax as the inner phase of the oil-in-water droplets. The optimization of the preparation strategy was supported by both optical microscopy and scanning electron microscopy, which allowed us to show the morphological features of the prepared hybrid systems and their structural properties, i.e., the distribution of the clay at the interface. Also, the dependence of the overall dimensions of the prepared systems on the halloysite content was demonstrated. Microdifferential scanning calorimetry (μ-DSC) was conducted in order to assess whether the thermal properties of the wax are affected after its interaction with HNTs. Then, the Pickering emulsions were employed for the treatment of waterlogged wooden samples. Compared to the archeological woods treated with pure wax, the addition of nanotubes induced a remarkable improvement in the mechanical performance in terms of stiffness and flexural strength. The proposed protocol is environmentally friendly since water is the only solvent used throughout the entire procedure, even if wax is vehiculated into the pores at room temperature. As a consequence, the design of wax/halloysite Pickering emulsions represents a promising strategy for the preservation of wooden artworks, and it has a great potential to be scaled up, thus becoming also exploitable for the treatments of shipwrecks of large size.

Highlights

IntroductionThe consolidation and protection of historical artifacts have attracted the interest of many researchers due to their great importance as evidence of the past and for the difficulty to fulfill this extremely complex purpose.[1] Within this field, the conservation of waterlogged archeological woods is a critical issue.[2] After several centuries in marine or anoxy and humid environments, where the wooden structures are preserved by low temperatures and low amounts of oxygen, preventing their collapse upon recovery and drying represents the most challenging task.[3] Under water, the wood loses mechanical resistance because of the degradation of lignocellulosic polysaccharides and lignin carried out by bacteria and fungi.[4,5] the main concern related to the drying process is the loss of the original structure and, the loss of the historical artwork itself.[6] New protocols have been developed for the conservation of cultural heritage.[7,8] Colloidal engineering has become a deeply investigated research domain, and many synthetic routes have been proposed for chemists and materials scientists.[9−12]
In recent years, the consolidation and protection of historical artifacts have attracted the interest of many researchers due to their great importance as evidence of the past and for the difficulty to fulfill this extremely complex purpose.[1]
The decrease of ΔHm after the addition of halloysite is due to the presence of the nanotubes, which partially destroy the crystallinity of paraffin, as observed for both beeswax and mineral wax.[60]

Summary

Introduction

The consolidation and protection of historical artifacts have attracted the interest of many researchers due to their great importance as evidence of the past and for the difficulty to fulfill this extremely complex purpose.[1] Within this field, the conservation of waterlogged archeological woods is a critical issue.[2] After several centuries in marine or anoxy and humid environments, where the wooden structures are preserved by low temperatures and low amounts of oxygen, preventing their collapse upon recovery and drying represents the most challenging task.[3] Under water, the wood loses mechanical resistance because of the degradation of lignocellulosic polysaccharides and lignin carried out by bacteria and fungi.[4,5] the main concern related to the drying process is the loss of the original structure and, the loss of the historical artwork itself.[6] New protocols have been developed for the conservation of cultural heritage.[7,8] Colloidal engineering has become a deeply investigated research domain, and many synthetic routes have been proposed for chemists and materials scientists.[9−12]

Objectives

Methods

Results

Conclusion