Application And Mechanism Of Furfuryl Alcohol In Reinforcement Of Waterlogged Archaeological Wood

Cultural relics carry many kinds of information of human history,which are non-replicable,non-renewable and of great research value.Archaeological relics left by different periods and groups are buried in various parts of our country.Among them,wood,as an easy-to-obtain and easy-to-process material,is common in various relics and sites.When the burial environment is relatively dry,the archaeological wood(AW)is mostly incomplete or completely decayed when unearthed;archaeological woods buried in saturated environments are usually well preserved,but they still need targeted protection.The purpose of this study is to provide a new method for the dehydration and consolidation of saturated waterlogged archaeological wood.The consolidation test was carried out on the sample numbered M105(the specie is Pinus massoniana)of the coffin floor unearthed from the Shimenkan cemetery site in the Qinhuai District of Nanjing in 2019.Furfuryl alcohol was used to replace the water in the saturated AW and reinforce the archaeological wood,while preserving the surface morphology of the AW to the greatest extent,and revealing the mechanism of furfuryl alcohol consolidation of the AW after the process treatment used in this experiment.The basic density and saturated water content of AW were 0.136g/cm~3 and 682.2%,respectively.The oven dry shrinkage of AW in radial,tangential,longitudinal and volume shrinkages were 35.2%,66.1%,22.8%and 78.0%,respectively.Based on the NREL test standard,the analysis of the main chemical components of AW showed that the contents of cellulose,hemicellulose and lignin were 19.07%,0.08%and 72.1%,respectively,and the degradation of holocellulose was very serious.XRD test results and polarized light microscope observation results show that the crystallinity of AW cellulose is extremely low,and the crystalline region is dim and sparse.Under SEM,the secondary wall of AW was seriously degraded,and the compound middle lamella was almost intact.There are round cavities and a large number of characteristic pores in the secondary wall,and hyphae appear in ray cells and tracheids.The above results indicate that the AW is in a state of severe degradation and is essential for consolidation with furfuryl alcohol.On the basis of pre-experiment,the simulation test of healthy Pinus massoniana showed that the WPG of Pinus massoniana impregnated by displacement method was higher than that of vacuum method.The WPG of consolidated archaeological wood(CAW)increased slowly after furfuryl alcohol concentration reached 30%.The results of colorimeter measurement showed that the surface color difference of CAW consolidated by’displacement+exposure’process was invisible to the naked eye.The internal color difference of CAW changes obviously.The above test results show that the’replacement method+unwrapped’improved process can reduce the surface color difference,ensure the weight gain rate,and meet the consolidation requirements.The radial,tangential,longitudinal and volume shrinkage of 50%furfuryl alcohol consolidation impregnating were 0.20%、0.35%、0.21%and 1.43%,the radial,tangential,longitudinal and volume ASE were 99.43%、99.47%、99.08%and 98.17%,respectively,and the effect was the best.There are no cracks and deformation on the surface of the CAW.The dimensional stability of CAW treated with three furfuryl alcohol consolidation impregnating solutions is relatively close.The dimensional stability of CAW increases with the increase of furfuryl alcohol consolidation.When the furfuryl alcohol concentration is higher than 10%,the improvement of dimensional stability slows down.The results of XRD and polarized light microscopy showed that the 18°peak in the XRD diffraction pattern of CAW completely disappeared after it was consolidation,and the crystallinity did not change significantly with the increase of furfuryl alcohol concentration in the impregnating,while the crystalline region basically disappeared when the furfuryl alcohol concentration rised to 30%.The results of hygroscopicity test showed that the hygroscopicity of CAW was greatly improved after consolidation:the fiber saturation point of CAW decreased from 22.20%to a minimum of 8.31%(when the furfuryl alcohol concentration was 50%),with an average decrease of 63.1%.The pore volume of CAW was significantly reduced after concentrated with furfuryl alcohol,and the pores with smaller pore size were first filled with furfuryl alcohol.The pore volume of pore size at 2～40 nm of the CAW was greatly reduced.With the increase of the concentration of furfuryl alcohol in the impregnation solution,the pore volume of the 20～100nm pore size of the CAW gradually decreased.The results of electron microscopy showed that when the furfuryl alcohol concentration was 10%,there were still a large number of pores in the cell wall of CAW.When the furfuryl alcohol concentration was 30%and 50%,the most cell wall was completely filled with furfuryl alcohol,and the cell wall was significantly hardened.When the concentration of furfuryl alcohol was 30%,furfuryl alcohol began to accumulate in the cell cavity.When the concentration of furfuryl alcohol in the impregnation solution was 50%,the accumulation of furfuryl alcohol in the cell cavity was aggravated.The results of fluorescence microscopy showed that furfuryl alcohol was mainly distributed in the secondary wall filled with pores and lignin,less than that in the composite intercellular layer,and there was no blockage in the cell cavity.According to the results of FTIR showed that furfuryl alcohol was successfully polymerized in CAW and ring-opening reaction occurred,forming a binary ketone structure.According to the results of 2D-HSQC NMR,it can be judged that the WML of CAW and furfuryl alcohol have a certain reaction.Based on the above conclusions,using the process in this paper,the use of furfuryl alcohol to concentrate the severely degraded AW has achieved good results.The dimensional stability of the CAW has been greatly improved,the hygroscopicity has decreased significantly,the pores of cell wall is are greatly reduced,the surface chroma changes slightly.Furfuryl alcohol preferentially filled pores with smaller pore size,and larger pores were gradually filled with the increase of consolidation of furfuryl alcohol.When the furfuryl alcohol concentration was 10%,the filling was not obvious,when it reached 30%,the CAW pores were initially filled completely,and furfuryl alcohol began to accumulate on the surface of the lumen and was mainly distributed in the secondary wall.The results of FTIR and NMR showed that furfuryl alcohol was polymerized in CAW and reacted with the Side-chain regions of WML of AW.