Evaluation of PEG and sugars consolidated fragile waterlogged archaeological wood using nanoindentation and ATR-FTIR imaging.

Waterlogged archaeological wood (WAW) undergoes biological deterioration during long-term immersion in microorganisms-rich aquatic environments. The consolidants are commonly applied to avoid wood deformation upon drying. It is urgent to develop a systematic evaluation method to study the impact of the consolidant distribution and the intermolecular interactions among consolidants and cell wall components on the improvement of wood mechanical traits. In order to evaluate the effect of consolidant distribution and intermolecular interactions between consolidants and cell wall components on the mechanical improvement, herein, we proposed in situ analysis methods involving Nanoindentation (NI) technology (without prior embedding) along with attenuated total reflection Fourier transform infrared imaging (ATR-FTIR imaging). Moreover, PEG, sucralose, and trehalose were chosen as representative consolidants to treat moderately deteriorated WAW because of their different molecular weights and different hydrophilic groups. Results showed that the mechanical improvement in consolidated WAW was significant. The elastic modulus and hardness of WAW after consolidation with PEG, sucralose and trehalose increased, with improvements of 15.3% and 34.8%, 43.9% and 49.5%, 31.9% and 6.4%, respectively, compared to untreated WAW. All three consolidants were found under scanning electron microscopy (SEM) to have filled wood cell lumens and mesopores in cell walls to different extents. ATR-FTIR imaging and thermogravimetric analysis (TGA) results further indicated that consolidants partly penetrated the wood cell walls. PEG was more concentrated near the fiber lumina. In addition, TGA revealed that the relative contents of PEG and trehalose in consolidated archaeological woods were 54.0% and 39.8%, and the maximum decomposition temperature (T d) of consolidated WAW all differed from the untreated WAW, which suggested non-covalent intermolecular interactions were probably presented between consolidants and WAW cell wall components. • Non-embedding sample preparation of Nanoindentation was developed for hydrophilic consolidants treated archaeological wood. • Nanoindentation method is feasible to characterize the mechanical property of consolidated archaeological wood. • ATR-FTIR imaging method proved distribution regularities of consolidants in cell wall of consolidated archaeological wood. • Consolidants PEG, sucralose and trehalose had interacted with cell wall components. [ABSTRACT FROM AUTHOR]