Evaluation of the reversibly cross-linked polymer-consolidated waterlogged archaeological woods from Zhangwan No.1 shipwreck

Abstract

Zhangwan No.1 Shipwreck, excavated in 2012, urgently requires the application of conservation materials to protect its waterlogged archaeological woods. In this work, reversibly cross-linked polymer (RCP) is employed as conservation materials to consolidate the waterlogged archaeological woods from Zhangwan No.1 Shipwreck and its corresponding consolidation effect is thoroughly evaluated. RCP-based conservation materials are constructed by penetrating 2-formylphenylboric acid modified polydimethylsiloxane (PPBA) into the waterlogged wood samples, and then in-situ reversibly cross-linking by N-coordinated boroxines (NCBs). In-situ formed reversibly cross-linked conservation materials (PNCB) can support the structure of the archaeological woods to improve their dimensional stability. The shrinkage rate of the PNCB-consolidated archaeological woods is ∼2.1% and its anti-shrinkage efficiency is ∼85.6%. Moreover, the PNCB-consolidated archaeological woods exhibit the excellent humidity stability and thermostability due to the stable cross-linking network of PNCB. Even under the environment with relative humidity of 100%, the equilibrium moisture content (EMC) of the PNCB-consolidated archaeological woods is only ∼0.4%, significantly lower than that of un-consolidated and polyethylene glycol-consolidated archaeological woods. Because the NCB cross-linkers can be broken by ethanol, the PNCB conservation materials within the archaeological woods can be depolymerized into PPBA and eliminated from the archaeological woods after ethanol immersion.