Acetyl Distribution in Acetylated Whole Wood and Reactivity of Isolated Wood Cell-Wall Components to Acetic Anhydride (original) (raw)
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Journal of Wood Science, 2004
A novel method for analysis of benzylic ether type lignin-carbohydrate bonds has been developed by using model compounds. Four diastereomers of model compound 3-(4-hydroxy-3-methoxyphenyl)-2-(2methoxyphenoxy)-3-(methyl-d-glucopyranoside-6-O-yl)-1-propanol (GGMGP), were ozonized in acetic acid/water/ methanol 16 : 3 : 1 for 1 h at 0°C. The product from ozonation of each diastereomer was saponified and the corresponding α-etherified tetronic acid (TAMGP) was isolated using ion exchange chromatography. Minor amounts of methyl-dglucopyranoside (MGP) and small amounts of a gluconic acid etherified with tetronic acid (TAGLCA), tetronic acid, gluconic acid, and glyceric acid were detected in the product mixture of ozonated benzylic ether type model compounds. The results suggest that a benzyl ether bond between lignin and carbohydrate is rather stable during the ozone treatment. Acid treatments with sulfuric acid or trifluoroacetic acid of the derived TAMGP led to cleavage of the gluco-sidic bond but only a small amount of products (tetronic acid and glucose) resulting from cleavage of the α-ether bond were formed. The successful chemical treatments were used for studies of benzylic ether bonds in Japanese red pine. The results suggest the presence of benzylic ether bonds to polysaccharides in the wood.
Acs Symposium Series, 2014
Wood is a porous three dimensional, hydroscopic, viscoelastic, anisotropic biopolymer composite composed of an interconnecting matrix of cellulose, hemicelluloses and lignin with minor amounts of inorganic elements and organic extractives. Some, but not all, of the cell wall polymer hydroxyl groups are accessible to moisture and these accessible hydroxyls form hydrogen bonds with water. As the water layers build up, the cell wall expands to accommodate the water resulting in an increase in wood/water volume up to the fiber saturation point. Increased moisture levels also offer a large variety of microorganisms the opportunity to colonize and begin the process of decay. If these accessible hydroxyl groups are chemically substituted with a larger and more hydrophobic chemical groups, the bonded chemical can expand the cell wall until it reaches its elastic limit. And if the hydrophobic nature of substituted groups sufficiently reduces the cell wall moisture levels, the wood will no longer support the colonization of microorganisms. This modified wood then achieves a high level of dimensional stability and durability. One technology that has now been commercialized to achieve these properties is acetylation: a reaction between the hydroxyl groups on the wood cell wall polymers with acetic anhydride. While all woods contain a low level of acetyl groups, increasing this acetyl content changes the properties and performance of the reacted wood. When a substantial number of the accessible hydroxyl groups are acetylated consistently across the entire cell wall, the wood reaches its highest level of dimensional stability and durability.
Industrial Crops and Products, 2007
From the perspective of the utilization of the wood waste from African timber industry in the field of wood/polymer composites, the reactivity of four tropical hardwood species from Gabon, Tesula gabonensis Pellegr (T. gabonensis), Holoptelea grandis Hutch (H. grandis), Aucoumea klaineana Pierre (A. klaineana Pierre) and Tieghemella africana Pierre (T. africana) towards succinic anhydride (SA) and 2-octen-1-yl succinic anhydride (OSA) was studied on the basis of their carbohydrate complex and lignin polymers structure and composition as well as on the basis of the capability of their wood cell walls to absorb the dimethylformamide (DMF) and pyridine (Py) solution. T. gabonensis, H. grandis and T. africana wood sawdust are more reactive with SA than A. klaineana. However, T. gabonensis is the most reactive with SA as well as with OSA. The better reactivity of T. gabonensis should be connected to the abundance of the reactive hydroxyl functions in its native lignin. Furthermore, T. gabonensis, H. grandis and T. africana are rich in long polysaccharide fibers; their cell walls displayed a strong capability for swelling after DMF/Py absorption than A. klaineana. The latter displays short polysaccharide fibers assumed to agglomerate within the cell walls, limiting like this the contribution of the polysaccharide chains located within A. klaineana cell walls on its chemical reactivity; protecting thereby its cellulose matrix from a decrystallization as pointed out by X-ray diffraction (XRD) analysis. The crystalline lattice of T. gabonensis, H. grandis and T. africana for which the cell walls are more accessible to DMF/Py exhibit the most important decrease of the crystallinity index (CrI) and the crystallite sizes (D 0 0 2 ).
The study of selected properties of pine wood (Pinus sylvestris L.) subjected to acetylation
Annals of WULS, Forestry and Wood Technology
The study of selected properties of pine wood (Pinus sylvestris L.) subjected to acetylation. In the paper pine wood was subjected to acetylation with acetic anhydride and mixture of acetic anhydride and glacial acetic acid (50:50)v/v. After modification process density, WPG index, water absorbability, volume swelling and colour of wood were carried out and compared with results obtained for unmodified pine wood. Based on the obtained results the density of acetylated pine wood was increased for each group of samples. The highest WPG index was obtained for previously dried wood modified with acetic anhydride (15.6%) or mixture of acetic anhydride and glacial acetic acid (10.5%). Acetylation process with acetic anhydride or mixture of acetic anhydride and glacial acetic acid of samples, which were extracted (in chloroform-ethanol 93:7w/w mixture) and dried before modification, had beneficial effect on water absorbability of pine wood. These samples after 1001h (about 42 days) of soak...
Biological attack of acetylated wood
Acetylation is an environmental friendly method to modify wood properties and protect it against biological attack. Many researches have been done in this field. However, no concern was paid for mode of protection in acetylated wood. This research had been aimed to study mode of action in acetylated wood by investigating on weight and MOE loss, chemical alteration in cell wall due to microbial attack, IRspectroscopy, microcalorimetry, determination of fungal biomass by using ergosterol assay and FDA hydrolysis and enzyme assays. Beech and Scots pine wood samples were acetylated by using acetic anhydride at temperature 80-120°C for 180min. Acetylated wood samples were tested under soil bed test condition, filed and basidiomycete trials. Results showed that the losses of weight and MOE decreased at increasing weight gains. Soil bed test revealed that the acetylation of beech wood at above 8% and pine wood at above 10% inhibits soil microorganisms in attacking wood and their activities reached to nil at higher weight gains. A test with the white rot fungus (T. versicolor) showed that the weight loss decreased at raising weight gains. Weight gains of above 10% inhibited fungal decay in beech wood and it reached to zero at higher weight gains. Microscopical studies of wood from soil bed samples, field trials and basidiomycete (white-and brown-rot) tests showed that fungi could colonize acetylated and non-acetylated wood. However, measurements of fungal biomass by using ergosterol assays in those woods and fluorescein diacetate in white rot tests showed a rapid colonization of fungal hyphae at early stages of incubation and decreased amount of fungal biomass at raising weight gains. Results showed that fungal colonization is influenced by the acetylation. Biological activities were measured in wood by using microcalorimetry. The reduction of thermal powers and measured amounts of energy production in acetylated wood revealed that activities of microorganisms were influenced by the acetylation and their activities decreased at increased degree of the acetylation. Microscopy of field trial samples showed that the acetylation of wood was affected the growth of soil microorganisms and protected wood against soil microorganisms during a long period of exposure (350 weeks) to soil. Different types of decay in field samples showed successional activities of soft-and white-rot fungi and also bacteria. Soil bed test showed a synergism between soil fungi and bacteria in wood. It was revealed that bacteria followed hyphal traces in cells and associated with fungi in wood degradation. Chemical analyses of acetylated wood in soil bed samples showed a significant effect of the acetylation on removal of cell wall components. The analyses showed a reduction in removal of cell wall components at increased weight gains. Results revealed that removal of the cell wall components reduced considerably in beech wood at weight gains above 8% and in Scots pine samples at above 10%. Study on patterns and phenology of white-and brown-rot decay on acetylated wood showed no difference of decay patterns between acetylated and non-acetylated wood, however decay patterns appear more later in acetylated wood.
Interactions between Wood Polymers in Wood Cell Walls and Cellulose/Hemicellulose Biocomposites
A wood fibre is a complex multi component biocomposite that is hierarchically organised. The arrangement of a wood fibre on the ultrastructural level is highly controlled by the interactions between the main structural polymers, i.e. cellulose, various hemicelluloses and lignin, as well as in some parts also pectin and protein. This further determines the mechanical and physical properties of the wood material, and consequently its targeted applications. Despite considerable research in this field during a number of years, the current knowledge on the interactions between the wood polymers is still incomplete and needs improvement. Also, mimicking of natural structures is an inspiration when preparing new materials from renewable resources, hence a comprehensive understanding of the polymer interactions is required. The first part of this study was to improve the understanding on the molecular interactions within the primary cell wall of spruce wood fibres, and its importance for th...