Abstract
Studies on new conservation agents for waterlogged archeological wood require vast amounts of similar wooden material. Therefore, model wood is useful for this purpose. The goal of the present research was to determine the mechanism of wood stabilization by organosilicon compounds to understand their mode of action and thus inform how to more effectively apply them to preserve various wooden artifacts. The study used chemically (ChP) and biologically degraded (BP) model Scots pine wood treated with Methyltrimethoxysilane (MTMS), (3-Mercaptopropyl)trimethoxysilane (MPTMS), or 1,3-Bis(diethylamino)-3-propoxypropanol)-1,1,3,3-tetramethyldisiloxane (DEAPTMDS). Synchrotron-based X-ray fluorescence microscopy (XFM) was used to investigate the penetration of organosilicons into the wood cellular structure and cell walls, and nanoindentation was used to study the mechanical properties of the treated wood cell walls. All treatments resulted in high volumetric anti-shrink efficiency (ASE(V)) values of 74-82%, except for MTMS-treated ChP with an ASE(V) of 52%. The multiscale XFM results revealed that all applied organosilicons penetrated throughout the whole wooden blocks and deposited in both cell lumina and cell walls. The retention of all applied organosilicons was highest in BP wood, and so was the dimensional stabilization effect. MTMS-treated ChP had the lowest measured cell wall infiltration, which likely contributed to its lower ASEv. DEAPTMDS treatments plasticized the cell walls and resulted in lowered nanoindentation elastic modulus (E (s) (NI)) and hardness (H) for all types of wood. MTMS and MPTMS had modest effects on cell wall mechanical properties and the effect depended on the type or wood. The final effect of organosilicon treatment on the dimensional wood stabilization and mechanical properties of wood cell walls depended not only on the type of the applied organosilicon, but also the properties of treated wood. This means that the treatment cannot be considered universal and individual approach is needed for the conservation of individual wooden objects. Although some mechanisms are now better understood, such as the need for organosilicons to infiltrate the cell walls and the plasticizing effect of DEAPTMDS, other aspects will benefit from more detailed analysis of the molecular interactions between organosilicons and wood polymers.