Organosilicons of different molecular size and chemical structure as consolidants for waterlogged archaeological wood \u2013 a new reversible and retreatable method

Magdalena Broda,Carmen-Mihaela Popescu,Izabela Dąbek,Michał Dutkiewicz,Agnieszka Dutkiewicz,Hieronim Maciejewski,Bartłomiej Mazela

doi:10.1038/s41598-020-59240-8

Abstract

Ineffectiveness of the chemicals applied so far for waterlogged wood conservation created the need to develop new more, efficient and reliable agents. As an alternative, a new method with the use of organosilicon compounds differing in chemical composition and molecular weight has been investigated. The results obtained show the potential of organosilicons as consolidants in waterlogged wood conservation able to effectively stabilise wood dimensions upon drying. The best wood stabilisers were low-molecular organosilicons enable to penetrate the cell wall as well as chemicals with functional groups capable of interacting with wood polymers and forming stabilising coatings on the cell wall surface. The best anti-shrink efficiency values were obtained for (3-Mercaptopropyl)trimethoxysilane, (3-Aminopropyl)triethoxysilane, 1,3-Bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, reaching 98, 91 and 91%, respectively. Most of the applied organosilicons reduced wood hygroscopicity, which limits the risk of further dimensional changes of wood exposed to a variable air moisture content and potentially reduces wood biodegradation. In the light of our studies, the proposed method of waterlogged wood conservation with organosilicons is potentially reversible in the case of siloxanes and amino-silanes as well as retreatable, which complies with the requirements of the conservation ethics.

Highlights

Wooden Cultural Heritage constitutes priceless evidence of human history
Some new multi-functional systems are being developed providing consolidation and simultaneous deacidification of wood, such as nanocomposites made of propylene glycol-modified silane and nanostructured calcium hydroxide[18] or polyethylene glycol and halloysite nanotubes containing calcium hydroxide[19], as well as a supramolecular polymer network system based on functionalised natural polymers that faces simultaneously three different issues connected with waterlogged wood: instability on drying, chemical degradation promoted by Fe3+-catalysed synthesis of acids and biological degradation[20]
The increased masses of the samples confirm an efficient impregnation of wood by the applied chemicals, whereby the correlation between the molecular weight of organosilicon particles and their relative number absorbed in wood can be seen (Fig. 1)

Summary

Introduction

Wooden Cultural Heritage constitutes priceless evidence of human history. to pass on our culture and traditions to future generations and help forge the sense of identity of modern societies, we are obliged to ensure its proper protection and conservation. Wood treatment with chemicals with the smallest molecules (MTMS, BAPTMDS, MPTMS) resulted in a good dimensional stabilisation with Sv between 1 and 10% (for comparison – untreated samples shrunk by 52%), which may be explained by their ability to penetrate the cell wall enhancing its structure.

Results

Conclusion