Strong/Stiff Exterior and Elastic Interior: An Effective Biomimetic Topological Structure for the Consolidation of Waterlogged Wooden Archaeological Relics during Dehydration

Abstract

Waterlogged wooden archaeological relics are prone to lose their dimensional and mechanical stability during dehydration, thus developing a green/effective strategy for consolidating a waterlogged wood upon its drying has drawn tremendous attention. Inspired by the specific topological structure and superior mechanical properties of human bone, we reported an environmentally friendly biomimetic consolidation method for restoring the waterlogged wood in this work. Briefly, branched PEI (poly(ethylenimine)) molecules were first incorporated into the waterlogged wood matrix by submerging to formulate a spongy interior, mimicking the structure of cancellous bone; then, GA (glutaraldehyde) solution or BDDE (1,4-butanediol diglycidyl ether) solution was sprayed onto the surface of a PEI-treated sample to form a dense exterior, mimicking the structure of cortical bone. Through two systematic orthogonal experiments, we identified the feasibility of this strategy and screened out the optimum feeding composition of the three reagents (10 wt % PEI, 6 wt % GA, and 3 wt % BDDE). As to targeted samples (10 wt % PEI + 6 wt % GA and 10 wt % PEI + 3 wt % BDDE), their dimension shrinkage rates along the X-, Y-, and Z-axis were all below or close to 3%. To figure out whether the rationale behind this strategy fitted well with our theoretical assumption, we first investigated the composition and structure of the BDDE/PEI-and GA/PEI-treated waterlogged wood samples through scanning electron microscopy (SEM), Fourier transform infrared spectrum (FT-IR), thermogravimetric−differential thermal (TGA−DTA) coupling tests, etc. and proved their biomimetic structure. Next, we explained the consolidation mechanism of this method by analyzing the crystalline phase and mechanical properties of the BDDE/PEI-or GA/PEI-treated samples. We thought that PEI induced the noncovalent cross-linking and BDDE-or GA-induced covalent cross-linking-mediated ordered arrangement of cellulose along different planes at the edge and middle of the waterlogged wood, respectively, therefore constructing a strong/stiff exterior and an elastic interior. Because of this specific biomimetic structure, the BDDE/PEI-or GA/PEI-treated waterlogged wood demonstrated simultaneously high strength, stiffness, and mechanical buffer capability and therefore could resist shrinkage stress and maintain high dimensional stability upon drying.

Consolidating Rotten/Pulverized Silk Fabrics through Spatially Adaptive 3D Strong/Tough Framework Mediated Structural Shaping of Fiber Bundles

“…To prove the incorporation of PEGDE molecules, we investigated the relative contents of C-O-C groups (ether) of the original SF, the RPSF, and the PEI/PEGDE/IPP treated SF (Table .S4). The decrease of the relative intensity of I1162/I3073 of the PEI/PEGDE/IPP treated SF, compared to that of the original SF and the RPSF, proved the presence of PEGDE 19,27 . In addition, the FT-IR spectra in the range of 1300 cm -1 to 1180 cm -1 (amide III band) were fitted and the corresponding peaks were separated to investigate the structural change of SF (Fig.…”

“…C-H groups of aromatic rings 23 . Considering the aromatic rings couldn't be degraded during the simulated rot/pulverization process, this peak, therefore, was utilized a benchmark 19 . Both the original SF and the RPSF demonstrated obvious absorbance peaks of amide I (C=O stretching, 1620 cm -1 ), amide II (N-H bending, 1514 cm -1 ), amide III (C-N stretching, 1444 cm -1 /1226 cm -1 ), and amide IV (694 cm -1 ) 24 .…”

“…Sericin could reinforce the mechanical strength of aged silk fabric to some extent, but the shaping function was inferior 18 . PEI (Mw 600) molecules have abundant NH2 groups, they are soluble in ethanol but insoluble in acetone 19 . PEGDE (Mw 400) molecules have abundant epoxy groups, they are soluble in acetone solution but insoluble in ethanol 20 .…”

Advances in historical wood consolidation and conservation materials

“…For example, biomineralization has been used for artificial bone materials (Thackray et al 2004) as well as highly durable non-organic "wood" (Shin and Exarhos 2007). Regarding the consolidation of waterlogged heritage wood, Li et al (2022) constructed a skeleton-like topology combining a rigid exterior with an elastic interior by immersing PEI (poly(ethyleneimine)) molecules into the wood matrix and then spraying GA (glutaraldehyde) or BDDE (1,4-butanediol diglycidyl ether) solution onto the wood surface (Fig. 9 A).…”

Resisting Pulverization of Silk Cultural Relics through 3D Structural Shaping and Mechanical Reinforcement

“…20 Poly(ethylenimine) (PEI) (M w : 600) molecules have abundant NH 2 groups; they are soluble in ethanol but insoluble in acetone. 21 Poly(ethylene glycol) diglycidyl ether (PEGDE) (M w : 400) molecules have abundant epoxy groups; they are soluble in acetone solution but insoluble in ethanol. 22 Isopropyl palmitate (IPP), an colorless oily emollient, has excellent softening function against proteins as well as outstanding chemical stability in air.…”