基于糠醇改性的木材细胞壁孔隙变化对水分的影响

王凯清; 周子懿; 马尔妮

doi:10.12171/j.1000-1522.20230156

基于糠醇改性的木材细胞壁孔隙变化对水分的影响

doi: 10.12171/j.1000-1522.20230156

北京林业大学材料科学与技术学院，木材科学与工程北京市重点实验室，北京 10083

基金项目: 国家自然科学基金项目（31971583）。

详细信息

作者简介:
王凯清。主要研究方向：木材保护与改性。Email：wkq15203318229@163.com　地址：100083 北京市海淀区清华东路 35 号北京林业大学材料科学与技术学院

责任作者:
马尔妮，教授。主要研究方向：木材物理、木材保护与改性。Email：maerni@bjfu.edu.cn　地址：同上。

中图分类号: S781.33
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出版历程
- 收稿日期: 2023-06-22
- 修回日期: 2023-09-07
- 录用日期: 2023-09-08
- 网络出版日期: 2023-09-11

Effects of cell wall pore changes on water of wood modified by furfuryl alcohol

Beijing KeyLaboratory of Wood Science and Engineering, College of Materials Science and Technology, Beijing Forestry University, Beijing 100083, China

摘要

摘要: 目的为进一步分析木材细胞壁与水分之间的相互作用，探究了糠醇改性前后木材细胞壁在典型水分状态下物理环境（孔隙）的变化规律和细胞壁水分的结合状态。方法以速生青杨（Populus cathayana）为研究对象，利用糠醇改性改变木材细胞壁水分存在的物理环境，分别利用扫描电镜、激光共聚焦显微镜、傅里叶红外光谱和氮气吸附法考察绝干状态下改性材的微观形貌、改性剂分布、官能团和孔隙结构，并利用差示扫描热孔计法和二维低场核磁共振技术分析低湿、气干、高湿和纤维饱和状态下改性前后木材细胞壁物理环境的变化规律以及细胞壁水分的结合情况。结果糠醇改性后木材的质量增长率、体积增长率分别为35.1%和12.6%，并伴随细胞壁增厚现象。改性后木材细胞壁的比表面积和孔体积分别降低了29.9%、35.3%，糠醇树脂堵塞了木材细胞壁的部分孔隙。从低湿状态到纤维饱和状态，未处理材和改性材孔体积均呈现增加趋势，未处理材细胞壁孔径分布极大值从3.41 mm³/g增加到5.65 mm³/g，增加了65.7%，糠醇改性材细胞壁孔径分布极大值从2.99 mm³/g增加到4.63 mm³/g，增加了54.9%。在不同水分状态下，糠醇改性材的细胞壁孔体积均低于未处理材，并且在高湿环境下，水分对木材细胞壁孔体积影响更加明显。随着相对湿度升高，未处理材和糠醇改性材的含水率都增加，但是糠醇改性材含水率低于同等条件下的未处理材，吸湿性降低。含水率增加，未处理材和糠醇改性材细胞壁水分T₁/T₂值降低，水分移动性增加。糠醇改性材中两种细胞壁水分的T₁/T₂值远高于未处理材，进一步说明糠醇改性改变了木材细胞壁的物理环境，限域空间束缚增加使得水分子移动性降低。结论经糠醇改性后，糠醇树脂进入木材细胞壁并发生原位聚合，造成在绝干、低湿、气干、高湿、纤维饱和状态下，改性材细胞壁孔体积均低于未处理材，并且在高湿度状态下，孔体积表现出更大的增长率。物理环境的变化造成木材细胞壁容纳水分的空间减少，同时，水分子受到细胞壁的物理束缚增加，移动性降低。
- 木材细胞壁 /
- 木材水分 /
- 相互作用 /
- 糠醇改性 /
- 孔隙结构
Abstract: Objective In order to further analyze the interaction between wood cell wall and water, the changes of physical environment (pores) and the binding state of water of wood cell wall before and after furfuryl alcohol modification were investigated. Methods The fast-growing poplar (Populus cathayana) was taken as the research object, and the physical environment of water in the wood cell wall was modified by furfuryl alcohol. The microscopic morphology, modifier distribution, functional groups and pore structure of the modified wood were characterized by scanning electron microscopy, confocal laser scanning microscope, Fourier transform infrared spectrometer and nitrogen adsorption under oven-dry state. Besides, differential scanning calorimetry thermoporosimetry and two dimensional low field nuclear magnetic resonance were used to analyze the changes of physical environment and the binding of water in the cell wall before and after modification under low humidity, air-dry, high humidity and fiber saturation state. Results The mass percent gain and bulk percent gain of wood modified by furfuryl alcohol were 35.1% and 12.6%, respectively, accompanied by cell wall thickening. After modification, the specific surface area and pore volume of wood cell wall were reduced by 29.9% and 35.3%, and furfuryl alcohol resin blocked part of the pores in wood cell wall. From the low humidity state to the fiber saturation state, the pore volume of both untreated and furfuryl alcohol modified wood showed an increasing trend, and the maximum distribution of cell wall pore size of untreated wood ranged from 3.41 to 5.65 mm³/g, at an increase of 65.7%. The maximum cell wall pore size distribution of furfuryl alcohol modified wood rose from 2.99 to 4.63 mm³/g, increased by 54.9%. Under different water conditions, the pore volume of furfuryl alcohol modified wood was all lower than that of untreated wood. Moreover, at high relative humidity, the effect of water on the pore volume of wood cell walls was more pronounced. With the increase of relative humidity, the moisture content of both untreated wood and furfuryl alcohol modified wood became greater, while the moisture content of furfuryl alcohol modified wood was lower compared with that of untreated wood under the same conditions, suggesting a reduction in hygroscopicity. As the moisture content increased, the T₁/T₂ value of cell wall water in untreated and furfuryl alcohol modified wood decreased, and the water mobility enhanced. The T₁/T₂ values of two types of cell wall water in furfuryl alcohol modified wood were much higher than those in untreated wood, which further indicated that furfuryl alcohol modification changed the physical environment of cell wall, and the mobility of water molecules weakened with the increasing bound of confining space. Conclusion After modification by furfuryl alcohol, furfuryl alcohol resin entered the cell wall of wood and polymerized in situ, resulting in lower cell wall pore volume of modified wood than that of untreated wood under oven dry, low humidity, air-dry, high humidity and fiber saturation state. Besides, in the high humidity state, the pore volume showed a greater growth rate. The variations in the physical environment gave rise to a decrease in the space of wood cell walls to hold water, and at the same time, the physical binding of water molecules by the cell wall increased, leading to a decrease in mobility.
- wood cell wall /
- wood water /
- interaction /
- furfuryl alcohol modification /
- pore structure

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图 1 未处理材和糠醇改性材的扫描电镜、激光共聚焦图像

Figure 1. SEM and CLSM images of untreated wood and furfuryl alcohol modified wood

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图 2 未处理材和糠醇改性材的红外谱图分析

Figure 2. FTIR analysis of untreated wood and furfuryl alcohol modified wood

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图 3 绝干状态下未处理材与糠醇改性材氮气吸附与脱附等温线

Figure 3. Nitrogen adsorption and desorption isotherms of untreated wood and furfuryl alcohol modified wood under oven-dry state

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图 4 绝干状态下未处理材与糠醇改性材细胞壁孔径分布

Figure 4. Pore size distribution in cell wall of untreated wood and furfuryl alcohol modified wood under oven-dry state

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图 5 不同水分状态下未处理材（a）与糠醇改性材（b）在20 nm以下的细胞壁孔径分布

Figure 5. Pore size distribution in cell wall under 20 nm of untreated wood (a) and furfuryl alcohol modified wood (b) under different water states

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图 6 不同水分状态下20 nm以下孔径分布的比较

Figure 6. Comparison of pore size distribution for the samples under 20 nm under different water states

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图 7 不同水分状态下未处理材（a）与糠醇改性材（b）在20 nm以下的细胞壁累计孔体积分布

Figure 7. Cumulative pore volume distribution of cell wall below 20 nm for untreated wood (a) and furfuryl alcohol modified wood (b) under different water states

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图 8 不同水分状态下未处理材（a）和糠醇改性材（b）的T₁-T₂相关谱图

Figure 8. T₁-T₂ correlation spectra of untreated wood (a) and furfuryl alcohol modified wood (b) under different water states

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表 1 不同孔径对应的温度和保温时间

Table 1. Temperature and holding time corresponding to different pore sizes

孔径 Pore size/nm	温度 Temperature/℃	保温时间 Holding time/min
孔径 Pore size/nm	温度 Temperature/℃	低湿状态 Low humidity state	气干状态 Air-dry state	高湿状态 High humidity state	纤维饱和状态 Fiber saturation state
1.6	−40.0	8	8	8	8
1.8	−30.0	3	3	3	3
2.5	−21.0	3	3	3	3
4.0	−11.6	3	3	3	3
6.0	−7.3	3	3	3	3
7.9	−5.4	3	3	3	3
10.0	−4.2	3	3	3	3
14.7	−2.8	3	3	3	3
20.4	−2.0	3	3	3	3
31.1	−1.3	3	3	3	3
50.1	−0.8	3	3	3	3
99.6	−0.4	3	3	3	3
396.6	−0.1	3	3	3	3
注：表中数据引自参考文献[7]。Note: data in the table are cited from reference [7].

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表 2 改性前后木材的比表面积和20 nm以下孔体积变化

Table 2. Changes of specific surface area and pore volume of wood under 20 nm before and after modification

试样 Sample	S_BET/（m²·g⁻¹）	V₂₀/（mm³·g⁻¹）
未处理材 Untreated wood	2.94	2.49
糠醇改性杨木 Furfuryl alcohol modified wood	2.06	1.61
注：S_BET为BET测得的孔隙比表面积；V₂₀为吸附曲线中利用BJH法计算的20 nm以下孔体积。Notes: S_BET is the pore specific surface area measured by BET method; V₂₀ is the pore volume under 20 nm calculated by the BJH method in adsorption curve.

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表 3 不同水分状态下试样两种细胞壁水的含水率和弛豫特性

Table 3. Moisture content and relaxation characteristics for the two types of cell wall water in the samples under different water states

组别 Sample	相对湿度条件 Relative humidity condition	E_MC/%	E_MCB/%	E_MCC/%	T_1B/ms	T_1C/ms	T_2B/ms	T_2C/ms	T_1B/T_2B	T_1C/T_2C
未处理材 Untreated wood	低湿状态 Low humidity state	3.45	3.40	0.05	160.22	7.62	0.32	0.45	493.08	16.92
	气干状态 Air-dry state	7.52	5.98	1.54	115.61	6.13	1.20	1.20	96.44	5.11
	高湿状态 High humidity state	12.09	10.46	1.63	115.61	5.50	2.30	1.85	50.21	2.97
	纤维饱和状态 Fiber saturation state	23.26	22.19	1.07	143.71	6.13	2.57	2.57	55.98	2.39
糠醇改性材 Furfuryl alcohol modified wood	低湿状态 Low humidity state	2.21	2.21	—	178.64	—	0.23	—	761.89	—
	气干状态 Air-dry state	4.48	4.11	0.37	115.61	2.86	0.45	0.36	256.71	7.90
	高湿状态 High humidity state	8.97	8.39	0.58	103.69	2.07	0.70	0.56	149.01	3.69
	纤维饱和状态 Fiber saturation state	18.81	16.06	0.44	143.71	2.86	0.86	0.96	133.65	2.97
注：E_MC、E_MCB、E_MCC分别为样品在不同水分状态下的总含水率、B水含水率和C水含水率；T_1B、T_1C分别为B水、C水的纵向弛豫时间；T_2B、T_2C分别为B水和C水的横向弛豫时间；T_1B/T_2B、T_1C/T_2C分别为B水、C水纵向弛豫时间与横向弛豫时间的比值。Notes: E_MC, E_MCB, and E_MCC represent the total moisture content, moisture content of B water and C water in the samples under different water states. T_1B and T_1C are the longitudinal relaxation time of B water and C water. T_2B and T_2C are the lateral relaxation time of B water and C water. T_1B/T_2B and T_1C/T_2C are the ratios of longitudinal relaxation time to transverse relaxation time for B water and C water.

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参考文献(29)

[1]	王哲, 王喜明. 木材多尺度孔隙结构及表征方法研究进展[J]. 林业科学, 2014, 50(10): 123−133. Wang Z, Wang X M. Research progress of multi-scale pore structure and characterization methods of wood[J]. Scientia Silvae Sinicae, 2014, 50(10): 123−133.
[2]	Zhao G J, Norimoto M, Yamada T, et al. Dielectric relaxations of water adsorbed on wood[J]. Mukuzai Gakkaishi, 1990, 36(4): 257−263.
[3]	马尔妮, 赵广杰. 木材物理学专论[M]. 北京: 中国林业出版社, 2012. Ma E N, Zhao G J. Special topics on wood physics[M]. Beijing: China Forestry Publishing House, 2012.
[4]	Shi J, Avramidis S. Dried cell wall nanopore configuration of Douglas-fir, western red cedar and aspen heartwoods[J]. Wood Science and Technology, 2018, 52: 1025−1037. doi: 10.1007/s00226-018-1011-4
[5]	Thybring E E, Fredriksson M. Wood modification as a tool to understand moisture in wood[J]. Forests, 2021, 12(3): 372. doi: 10.3390/f12030372
[6]	罗文圣, 赵广杰. 木材细胞壁的空隙构造及物质的输运过程[J]. 北京林业大学学报, 2001, 23(2): 85−89. doi: 10.3321/j.issn:1000-1522.2001.02.019 Luo W S, Zhao G J. Pore structure of cell wall of wood and transport processes of substance[J]. Journal of Beijing Forestry University, 2001, 23(2): 85−89. doi: 10.3321/j.issn:1000-1522.2001.02.019
[7]	仲翔, 张少军, 马尔妮. 不同含水率状态下木材细胞壁孔径分布变化[J]. 北京林业大学学报, 2021, 43(11): 128−136. doi: 10.12171/j.1000-1522.20210260 Zhong X, Zhang S J, Ma E N. Variation in pore size distribution of wood cell wall under different moisture states [J]. Journal of Beijing Forestry University, 2021, 43(11): 128−136. doi: 10.12171/j.1000-1522.20210260
[8]	马尔妮, 王望, 李想, 等. 基于LFNMR的木材干燥过程中水分状态变化[J]. 林业科学, 2017, 53(6): 111−117. doi: 10.11707/j.1001-7488.20170613 Ma E N, Wang W, Li X, et al. The states of water in wood during drying process studied by low-field nuclear magnetic resonance (LFNMR)[J]. Scientia Silvae Sinicae, 2017, 53(6): 111−117. doi: 10.11707/j.1001-7488.20170613
[9]	Bonnet M, Courtier-Murias D, Faure P, et al. NMR determination of sorption isotherms in earlywood and latewood of Douglas fir. identification of bound water components related to their local environment[J]. Holzforschung, 2017, 71(6): 481−490. doi: 10.1515/hf-2016-0152
[10]	Li J Y, Ma E N. Characterization of water in wood by time-domain nuclear magnetic resonance spectroscopy (TD-NMR): a review[J]. Forests, 2021, 12(7): 886. doi: 10.3390/f12070886
[11]	王立双. 基于近红外光谱的木材干缩湿胀研究[D]. 北京: 北京林业大学, 2018. Wang L S, Study on hygroexpansion of wood based on Near-Infrared Spectroscopy[D]. Bejing: Beijing Forestry University, 2018
[12]	孔丽琢. 糠醇树脂/磷酸二氢铵复合改性杨木性能研究[D]. 北京: 中国林业科学研究院, 2018. Kong L Z. The study on properties of poplar wood treated with furfuryl alcohol and ammonium dihydrogen phosphate[D]. Beijing: Chinese Academy of Forestry, 2018
[13]	冷魏祺, 何盛, 张雪峰, 等. 糠醇树脂改性木材机制的研究进展与思考[J]. 林业工程学报, 2021, 6(6): 35−43. Leng W Q, He S, Zhang X F, et al. Research progress and thoughts on the modification mechanism of wood furfurylation[J]. Journal of Forestry Engineering, 2021, 6(6): 35−43.
[14]	Dong Y, Qin Y, Wang K, et al. Assessment of the performance of furfurylated wood and acetylated wood: comparison among four fast-growing wood species[J]. BioResources, 2016, 11(2): 3679−3690.
[15]	李昀彦. 糠醇树脂改性重组竹制备技术研究[D]. 长沙: 中南林业科技大学, 2019. Li Y Y. Study on manufacturing technology of reconstituted bamboo modified by furfuryl alcohol[D]. Changsha: Central South University of Forestry and Technology, 2019.
[16]	杨甜甜. 湿度周期作用下糠醇改性杨木的水分吸着与变形响应机制[D]. 北京: 北京林业大学, 2020. Yang T T. Moisture sorption and deformation response mechanisms of furfurylated poplar wood to cyclically changing relative humidity[D]. Beijing: Beijing Forestry University, 2020.
[17]	李万菊. 木竹材糠醇树脂改性技术及其机理研究[D]. 北京: 中国林业科学研究院, 2016. Li W J. The study on the modification technology and mechanism of fururylation of wood and bamboo[D]. Beijing: Chinese Academy of Forestry, 2016.
[18]	Branaver S, Emmeff P H, Teller E. Adsorption of gases in multimolecular layers[J]. Journal of the American Chemical Society, 1938, 60(2): 309−319. doi: 10.1021/ja01269a023
[19]	Barrett E P, Joyner L G, Halenda P P. The determination of pore volume and area distributions in porous substances. Ⅰ. computations from nitrogen isotherms[J]. Journal of the American Chemical Society, 1951, 73(1): 373−380. doi: 10.1021/ja01145a126
[20]	Macromolecule Academy. Physical properties of macromolecules [M]. Tokyo: Kyoritsu Press, 1958.
[21]	Jackson C L, McKenna G B. The melting behavior of organic materials confined in porous solids[J]. Journal of Chemical Physics, 1990, 93(12): 9002−9011. doi: 10.1063/1.459240
[22]	Pranger L, Tannenbaum R. Biobased nanocomposites prepared by in situ polymerization of furfuryl alcohol with cellulose whiskers or montmorillonite clay[J]. Macromolecules, 2008, 41(22): 8682−8687. doi: 10.1021/ma8020213
[23]	Everett D H. Manual of symbols and terminology for physicochemical quantities and units, appendix Ⅱ: definitions, terminology and symbols in colloid and surface[J]. Chemistry. Pure and Applied Chemistry, 2013, 31(4): 577−638.
[24]	Grigsby W J, Kroese H, Dunningham E A. Characterisation of pore size distributions in variously dried Pinus radiata: analysis by thermoporosimetry[J]. Wood Science and Technology, 2013, 47(4): 737−747. doi: 10.1007/s00226-013-0537-8
[25]	Paajanen A, Zitting A, Rautkari L, et al. Nanoscale mechanism of moisture-induced swelling in wood microfibril bundles[J]. Nano Letters. 2022, 22(13): 5143-5150
[26]	Robinson N J O. Nuclear spin relaxation and diffusion studies of adsorption and dynamics at the catalyst-liquid interface[D]. London: University of Cambridge, 2020.
[27]	Cox J, Mcdonald P J, Gardiner B A. A study of water exchange in wood by means of 2D NMR relaxation correlation and exchange[J]. Holzforschung, 2010, 64(2): 259−266.
[28]	Engelund E T, Thygesen L G, Svensson S, et al. A critical discussion of the physics of wood-water interactions[J]. Wood Science and Technology, 2013, 47: 141−161. doi: 10.1007/s00226-012-0514-7
[29]	Kulasinski K. Physical and mechanical aspects of moisture adsorption in wood biopolymers investigated with atomistic simulations[D]. Zurich: ETH Zurich, 2015.