scholarly journals Sorption behavior and hydroxyl accessibility of wood treated with different cyclic N-methylol compounds

2020 ◽  
Vol 55 (35) ◽  
pp. 16561-16575
Author(s):  
Lukas Emmerich ◽  
Michael Altgen ◽  
Lauri Rautkari ◽  
Holger Militz
Keyword(s):  
Cell Wall ◽  
Treated Wood ◽  
Covalent Bond ◽  
Water Vapor Sorption ◽  
Adjacent Cell ◽  
Sorption Behavior ◽  
Moisture Uptake ◽  
Negative Effects ◽  
Oh Groups ◽  
Dimensional Changes

Abstract Cyclic N-methylol compounds such as 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) have been used to modify wood and prevent negative effects related to the uptake of moisture. However, the changes in the sorption behavior of wood by treatments with DMDHEU and its derivatives are not fully understood. In the present study, wood blocks were treated with DMDHEU, ether-modified DMDHEU and diethyleneglycolated DMDHEU in order to study the factors that control the changes in moisture uptake in the hygroscopic range (0–95% RH). Dimensional changes of wood blocks during water soaking cycles suggested that the treatments caused a permanent cell wall bulking, whereas the swelling restraint by cross-linking of adjacent cell wall polymers was not permanent. However, the changes in water vapor sorption were not only a result of the cell wall bulking effect that reduced the space in the cell wall to accommodate water. The N-methylol compounds within the wood also provided additional sorption sites, but there was no correlation between absorbed water and accessible OH groups. It was speculated that the co-condensation of the N-methylol compounds with wood polymers had a significant effect on the sorption of the treated wood. At elevated RH, pure resins that were formed by self-condensation took up large quantities of moisture. However, when the N-methylol compounds were heat-cured within the hierarchical structure of wood, the moisture uptake of the treated wood at elevated RH was even lower compared to unmodified wood. Furthermore, the covalent bond formation between wood and resin prolonged the attainment of an equilibrium moisture content.

Effects of acetylation and formalization on the dynamic water vapor sorption behavior of wood

Holzforschung ◽  
2015 ◽  
Vol 69 (5) ◽  
pp. 633-643 ◽  
Author(s):  
Sarah Himmel ◽  
Carsten Mai
Keyword(s):  
Cell Wall ◽  
Water Vapor ◽  
Relative Humidity ◽  
Water Vapor Sorption ◽  
Cross Linking ◽  
Sorption Behavior ◽  
Matrix Stiffness ◽  
Vapor Sorption ◽  
Dynamic Vapor Sorption ◽  
Cell Wall Polymers

Abstract The dynamic water vapor sorption of untreated, acetylated (Wac), and formaldehyde-treated (WFA) Scots pine (Pinus sylvestris L.) sapwood was studied in a dynamic vapor sorption apparatus to assess the effects of cell wall bulking and cross-linking. Both modifications resulted in a considerable reduction of reduced equilibrium moisture content (EMCR), the corresponding equilibrium times, and hysteresis in the hydroscopic range of wood. Acetylation reduced the adsorption and desorption of water at each given relative humidity (RH) step from 0% to 95% RH, whereas formalization affected the sorption behavior of wood solely above 20% RH. From 20% to 95% RH, the EMC ratio of WFA to its control steadily decreased, whereas the EMC ratio of Wac was still constant in this RH range. Below 20% RH, the sorption behavior of Wac was governed by hydroxyl blocking, whereas that of WFA was hardly influenced compared with the control. Above 20% RH, the sorption behavior of Wac was solely determined by cell wall bulking, whereas that of WFA was governed by the increased matrix stiffness due to the cross-linking of cell wall polymers.

scholarly journals Water vapor sorption behavior of bamboo pertaining to its hierarchical structure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Qi Chen ◽  
Changhua Fang ◽  
Ge Wang ◽  
Xinxin Ma ◽  
Junji Luo ◽  
...  
Keyword(s):  
Cell Wall ◽  
Water Vapor ◽  
Moisture Content ◽  
Moisture Transport ◽  
Water Vapor Sorption ◽  
Sorption Behavior ◽  
Sorption Rate ◽  
Vapor Sorption ◽  
Dynamic Vapor Sorption ◽  
Macro Scale

AbstractBamboo is an anisotropic, hierarchical, and hygroscopic material. Moisture transport in bamboo is one of the most fundamental properties affecting almost all other physical and mechanical properties of the material. This study investigated the water vapor sorption behaviors of bamboo at various structural levels: cell walls, cells (with pits) and bamboo blocks. The specimens with two sorption directions, longitudinal (L) and transverse (T), were measured by saturated salt solution method and dynamic vapor sorption. The parallel exponential kinetics model was used to analyze the sorption kinetics. The results showed that at the cell wall level, the sorption rate and equilibrium moisture content (EMC) of cell wall in the L specimens were larger than those in the T specimens. The differences were probably caused by the looser cell wall layers in the L specimens. At the cellular scale, pits in the cell wall resulted in an enhanced sorption rate and EMC of the T specimens compared with the L specimens where the pits in the parenchyma cells were only distributed in the lateral walls but not in end walls. At the macro scale, the sorption rate and moisture content of bamboo blocks were largely controlled by the vessel cells. As a hierarchically-structured plant, bamboo performs the biological function of moisture transport at all these scales. This work helps improve the understanding of water transport behavior in bamboo, which may lead to better bamboo drying and impregnation processes.

Sorption behavior and swelling of citric acid and sorbitol (SorCA) treated wood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Katarzyna Kurkowiak ◽  
Lukas Emmerich ◽  
Holger Militz
Keyword(s):  
Cell Wall ◽  
Citric Acid ◽  
Treated Wood ◽  
Underlying Mechanism ◽  
Cross Linking ◽  
Sorption Behavior ◽  
Dynamic Vapor Sorption ◽  
Wood Polymer ◽  
Modify Wood ◽  
Induced Changes

Abstract Citric acid together with sorbitol (SorCA) have been used to modify wood and improve its properties, such as dimensional stability and biological durability, which partly result from its swelling and sorption behavior. However, the underlying mechanism of water interaction with SorCA-treated wood is very complex and not fully understood. Previous research confirmed cell wall bulking and suggested cross-linking, however the extent of their contribution to moisture-induced changes has not been researched. This study investigated the effect of SorCA treatment on sorption properties of wood in the hygroscopic range (0–95% RH). Scots pine sapwood (Pinus sylvestris L.) was chemically modified with an aqueous SorCA solution at different treatment levels and measured by dynamic vapor sorption (DVS). The observed permanent increase in oven-dry dimensions did not result in a decreased swelling compared to untreated specimens. It was ascribed to the excessive expansion of cell wall matrix caused by a degradation of cell wall constituents by the acidic impregnation solution. However, a reduction in moisture content in comparison to untreated reference was detected. Present findings suggest that the SorCA polyester structure is altered after impregnation inside the wood and affects its sorption behavior by covalent bonding and, presumably, cross-linking with wood polymer constituents.

Ultrastructure of iodine treated wood

Holzforschung ◽  
2004 ◽  
Vol 58 (3) ◽  
pp. 219-225 ◽  
Author(s):  
L. Donaldson ◽  
A. Frankland
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Treated Wood ◽  
Cellulose Microfibrils ◽  
Adjacent Cell ◽  
Staining Reaction ◽  
Exact Nature ◽  
Iodine Staining ◽  
Reflectance Microscopy ◽  
Random Nature

Abstract Iodine staining has been used to study the orientation of cellulose microfibrils in wood using light microscopy. The aim of this work was to understand the exact nature of the staining reaction with iodine and to provide insight into the properties and organisation of the wood cell wall. Based on transmission electron microscopy it is apparent that precipitation of the iodine following treatment with nitric acid results in the formation of crystal cavities within the cell wall, which follow the orientation of the cellulose microfibrils. There is no evidence that iodine precipitates within “drying checks” as previously speculated. High resolution confocal reflectance microscopy of crystal cavity orientation indicates that the microfibril arrangement within pit borders can be both spiral and circular. Crystal cavities are much more abundant within the S1 layer than elsewhere. All of the cells examined had crystal cavities in the S1 region, which may be related to the reduced lignification at the S1/S2 boundary resulting in greater porosity of the cell wall at this location. Within the S2 region, clusters of crystal cavities are randomly distributed and occur in widely varying numbers among adjacent cell walls, suggesting variations in the porosity of the S2 wall within and among adjacent tracheids. Cavities form preferentially within more electron lucent regions of the cell wall. The random nature of crystal cavity formation within S2 clusters probably reflects the underlying random nature of the cell wall nanostructure. We conclude that iodine staining can provide important clues to the nanostructural properties of tracheid cell walls.

The preprophase band: possible involvement in the formation of the cell wall

1976 ◽  
Vol 22 (2) ◽  
pp. 403-411 ◽  
Author(s):  
M.J. Packard ◽  
S.M. Stack
Keyword(s):  
Cell Wall ◽  
Allium Cepa ◽  
Cell Walls ◽  
Preprophase Band ◽  
Adjacent Cell ◽  
Root Tips ◽  
Meristematic Cells ◽  
Narrow Region ◽  
The Matrix

Numerous vesicles were observed among the microtubules of the “preprophase” band in prophase cells from root tips of Allium cepa. The content of these vesicles looks similar to the matrix of adjacent cell walls, and these vesicles often appear to be involved in exocytosis. In addition, the cell walls perpendicular to the plane of (beneath) the preprophase band are often differentially thickened compared to the walls lying parallel to the plane of the band. Our interpretation of these observations is that the preprophase band may direct or channel vesicles containing precursors of the cell wall to localized regions of wall synthesis. The incorporation of constituents of the cell wall into a narrow region defined by the position of the preprophase band may be a mechanism that ensures unidirecitonal growth of meristematic cells.

Dimensional Changes in Corsican Pine Sapwood due to Chemical Modification with Linear Chain Anhydrides

Holzforschung ◽  
1999 ◽  
Vol 53 (3) ◽  
pp. 267-271 ◽  
Author(s):  
C.A.S. Hill ◽  
D. Jones
Keyword(s):  
Molar Volume ◽  
Linear Chain ◽  
Void Volume ◽  
Volume Increase ◽  
Oh Groups ◽  
Dimensional Changes ◽  
Low Weight ◽  
Weight Gains ◽  
Low Levels ◽  
The Relationship

Summary The volumetric changes in Corsican pine sapwood due to modification with an homologous series of linear chain anhydrides has been studied. The results have been interpreted in terms of the molar volume occupied by the substituent groups in the wood cell wall. At low levels of substitution, the molar volume is larger at low weight gains. Thus if the volume increase is due to a volume occupied by the reagent molecules and a void volume created within the wood matrix, then the void volume is larger at low levels of substitution. A non-linear relationship has also been found between the void volume and volume occupied by adduct as the size of the anhydride increases. By determining the relationship between average molar volume at high weight gains and ultimate level of OH substitution, for the range of anhydrides studied, it is possible to estimate the number of accessible OH groups at 5.7 (+/− 0.4) mMoles/gm, this contrasts with a theoretically calculated value of 8.6 mMoles/gm.

Microdistribution of copper in copper-ethanolamine (Cu-EA) treated southern yellow pine (Pinus spp.) related to density distribution

Holzforschung ◽  
2005 ◽  
Vol 59 (1) ◽  
pp. 82-89 ◽  
Author(s):  
Jinzhen Cao ◽  
D. Pascal Kamdem
Keyword(s):  
Cell Wall ◽  
Density Distribution ◽  
Cell Walls ◽  
Middle Lamella ◽  
Treated Wood ◽  
Yellow Pine ◽  
Using Data ◽  
Pinus Spp ◽  
Southern Yellow Pine ◽  
The Relationship

Abstract The relationship between copper absorption and density distribution in wood cell walls was investigated in this study. The density distribution on layer level was obtained from two approaches: (1) calculation by using data obtained from literature; (2) microdistribution of carbon and oxygen atoms in the wood cell. The microdistribution of carbon and oxygen in untreated southern yellow pine (Pinus spp.) sapwood, as well as copper in cell walls of copper-ethanolamine (Cu-EA) treated wood was determined by scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDXA). Both approaches for density distribution led to the same result: the density was higher in the compound middle lamella and cell corners than in the secondary wall. The concentration/intensity of Cu, C and O in the cell wall follow the same trend as the density distribution; suggesting that density may play a major role in SEM-EDXA study of the distribution of metal-containing wood preservatives within the wood cell wall.

Determination of the accessible hydroxyl groups in heat-treated Styrax tonkinensis (Pierre) Craib ex Hartwich wood by hydrogen-deuterium exchange and 2H NMR spectroscopy

Holzforschung ◽  
2007 ◽  
Vol 61 (5) ◽  
pp. 488-491 ◽  
Author(s):  
Le Xuan Phuong ◽  
Masato Takayama ◽  
Satoshi Shida ◽  
Yuji Matsumoto ◽  
Tetsuo Aoyagi
Keyword(s):  
Nmr Spectroscopy ◽  
Treated Wood ◽  
Deuterium Exchange ◽  
Fungal Resistance ◽  
Lower Amount ◽  
Hydroxyl Groups ◽  
Hydrogen Deuterium Exchange ◽  
Oh Groups ◽  
Heat Treated ◽  
Hydrogen Deuterium

Abstract A new approach based on hydrogen-deuterium exchange is proposed for measuring accessible OH groups in wood. The deuterium (D) exchanged for hydrogen in OH groups in wood was converted to D2O by combustion in oxygen gas then diluted in deionized water, and subsequently determined by 2H NMR spectroscopy. The amount of accessible OH groups in Styrax tonkinensis wood is approximately 6.8 mmol g-1. This measurement is very accurate, with an error of approximately 0.2 mmol g-1. Heat-treated wood has a lower amount of accessible OH groups than non-treated wood. This finding is in agreement with the decreased hygroscopicity of heat-treated wood and explains, at least partially, its increased fungal resistance.

Hydrophobisation of wood surfaces by combining liquid flame spray (LFS) and plasma treatment: dynamic wetting properties

Holzforschung ◽  
2016 ◽  
Vol 70 (6) ◽  
pp. 527-537 ◽  
Author(s):  
Maziar Sedighi Moghaddam ◽  
Golrokh Heydari ◽  
Mikko Tuominen ◽  
Matthew Fielden ◽  
Janne Haapanen ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Hydrophobic Effect ◽  
Treated Wood ◽  
Contact Angles ◽  
Sorption Behavior ◽  
Chemical Compositions ◽  
Flame Spray ◽  
Biological Degradation ◽  
Wood Surfaces ◽  
Liquid Flame Spray

Abstract The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which the nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate (mWP) method, resulting in advancing and receding contact angles as well as sorption behavior of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behavior. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.

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