Showing papers in "Wood Science and Technology in 1980"
TL;DR: In this paper, the behavior of lignin is explained as a competition between degradation reactions, mainly involving aryl ether cleavage with participation of neighboring groups, and condensation reactions, comprising conjugate addition of carbanions to quinone methide intermediates.
Abstract: Kraft pulping is interpreted in chemical terms on the basis of results from extensive qualitative and quantitative model experiments. In essence, the behavior of lignin is explained as a competition between degradation reactions, mainly involving aryl ether cleavage with participation of neighboring groups, and condensation reactions, comprising conjugate addition of carbanions to quinone methide intermediates. The initial phase of technical delignification is tentatively ascribed to the cleavage of α- and β-aryl ether bonds in phenolic lignin units, whereas the cleavage of β-aryl ether bonds in non-phenolic lignin units is considered to be the rate-determining reaction of the bulk phase. The residual phase may possibly be attributed to the rupture of C-C linkages and to aryl ether cleavage without neighboring group participation. Experimental support for these correlations is provided. The interplay of the various lignin reactions, illustrated in a summarizing scheme, explains some known observations in kraft pulping. Attention is drawn to analogies between reactions involved in the degradation of carbohydrates and those reponsible for the degradation of lignin. From the chemical standpoint, therefore, the selectivity of delignification is due to differences in the reactivity of the wood polymers, rather than to differences in the mechanisms of the degradation reactions. This fact explains the limitations of selective delignification.
378 citations
TL;DR: In this article, a lignin-carbohydrate material from black spruce (Picea mariana) was treated with a hemicellulase mixture, and the results obtained indicate that Lignin is bound to all types of sugar units in the hemiscale.
Abstract: A lignin-carbohydrate material from black spruce (Picea mariana) was treated with a hemicellulase mixture. The carbohydrates in the remaining material were studied by the following methods. a) Treatment with 0.1 M NaOH in the presence of sodium borohydride followed by selective hydrolysis of the furanosidic bonds, b) Smith degradation (periodate oxidation followed by mild acid hydrolysis). The results obtained indicate that lignin is bound to all types of sugar units in the hemicelluloses. For arabino-4-O-methylglucuronoxylan, linkages to the side-chain units seem to dominate. The links to the 4-O-methylglucuronic acid units are ester bonds, probably benzyl ester bonds. Those to the other sugar units in the hemicelluloses are ether bonds, probably benzyl ether bonds. The results suggest, furthermore, that fractions of cellulose are linked to lignin.
193 citations
TL;DR: In this paper, various degradation products from soft and hardwood lignins by hydrolysis with dioxanewater and catalytic hydrogenolysis are discussed and a structural model is proposed mainly based on these degradation products.
Abstract: Various degradation products from soft-and hardwood lignins by hydrolysis with dioxanewater and catalytic hydrogenolysis are discussed. And a structural model for softwood lignin is proposed mainly based on these degradation products. The model has 28 units and indicates good agreement with the various analytical data obtained so far in the lignin chemistry.
179 citations
TL;DR: The reactions of quinone methide intermediates during the initial biosynthesis and also the subsequent aging of lignin are reviewed in this article, which may explain the structural and analytical differences found between DHP and isolated milled wood lignins.
Abstract: The reactions of quinone methide intermediates during the initial biosynthesis and also the subsequent aging of lignin are reviewed. The reactions during aging should lead to enhanced lignin-carbohydrate bonding and may explain the structural and analytical differences found between DHP and isolated milled wood lignins.
44 citations
TL;DR: The disappearance of discrete cell wall layers was time-dependent as opposed to strictly temperature-dependent as discussed by the authors, which was attributed to the probable circumferential arrangement of cellulose, hemicellulose and lignin within the cell wall.
Abstract: Samples of Southern Pine (Pinus spp.) charred to 250°, 300°, 350°, 400° or 600°C in a flowing nitrogen atmosphere at rates of 1°, 10° and 50°C/min were examined using the scanning electron microscope to quantify changes in cross-sectional tracheid dimensions. The disappearance of discrete cell wall layers was time-dependent as opposed to strictly temperature-dependent. Tracheid diameters decreased in response to temperature and charring rate. Double cell wall thickness values also decreased in response to charring. This shrinkage was nearly isotropic. Below 300°C, latewood cells were more stable than earlywood cells. Above 300°C, the reverse was true. This was attributed to the probable circumferential arrangement of cellulose, hemicellulose, and lignin within the cell wall. The highest rate of thermal degradation was between 300° and 350°C.
33 citations
TL;DR: It is shown that the existence of the group of Sanio's four is better documented in the literature than has so far been recognized and the occurrence of a variable number of primary cell walls is discussed with reference to the concentration of lignin in the middle lamella of mature xylem.
Abstract: This electron microscopy study is concerned with the dormant cambial cells in compression wood of Picea abies (L.) Karst. The cambial zone comprised 4–8 rows of fusiform cells. Each radial file contained the group known as Sanio's four, namely an initial, a mother, and two daughter cells. Groups of three, resulting from a failure of a mother or a daughter cell to divide, were also present. Undifferentiated xylem tissue cells occurred singly, in pairs, or in groups of four. These cells and the last-formed tracheids were often enclosed by a common primary wall. The fusiform cells had a large, elongated nucleus, numerous small vacuoles, and a frequently infolded plasma membrane. Golgi apparatus and endoplasmic reticulum were rare, while plastids, amyloplasts, and lipid droplets were common. Cambial ray cells contained much lipid material. The tissues were similar to cambial tissues in normal wood of conifers. The present results can only be interpreted in terms of the single layer of initials and sequence of cell divisions established by Sanio. The initial can be located by several criteria in dormant and active cambial regions in conifers. It could be shown that the existence of the group of Sanio's four is better documented in the literature than has so far been recognized. The occurrence of a variable number of primary cell walls is discussed with reference to the concentration of lignin in the middle lamella of mature xylem.
31 citations
TL;DR: The literature from 1971 to 1979 concerned with the toxicity of products of combustion and/or pyrolysis of wood, or wood products, untreated or treated with preservatives as mentioned in this paper.
Abstract: Fuels such as wood and forest residuals are becoming important sources of energy; furthermore, wood and wood products are major components of building construction. In both cases environmental impact and health hazard posed by the burning of these materials must be evaluated. Most death and injuries on exposure to burning wood are due to inhalation of toxic gases, smoke, and heat gases, usually carbon monoxide. Any wood or wood products used in building construction must be chosen so as to release the minimum amount of toxic materials as slowly as possible when heated or burned, to allow people time to escape. The emissions from wood burning power plants certainly have local short term and global long term environmental impacts. For example, massive carbon dioxide production from wood burning is believed to affect the earth's energy balance and therefore global climates. This review does not consider this aspect of wood burning, or other environmental hazards due to power plants utilizing wood, about which little seems to be known. The subject of this review is of the literature from 1971–1979 concerned with the toxicity of products of combustion and/or pyrolysis of wood, or wood products, untreated or treated with preservatives.
27 citations
TL;DR: The technology and chemistry of recent advances in alkaline pulping are reviewed from the standpoint of the authors' work over the past few years in this paper, including sodaamine, soda-ethylenediamine (EDA), soda-anthraquinone (AQ), kraft, and soda-AQ/EDA pulping and their effects on pulp strength properties and bleachability.
Abstract: The technology and chemistry of recent advances in alkaline pulping are reviewed from the standpoint of the authors' work over the past few years. Topics reviewed include soda-amine [particularly soda-ethylenediamine (EDA)], soda-anthraquinone (AQ), kraft-AQ, and soda-AQ/EDA pulping and their effects on pulp strength properties and bleachability. There is evidence to support the concept that the rates of all alkaline delignification reactions, including kraft, are controlled by a reductive step which transfers electrons to the degrading lignin.
25 citations
TL;DR: In this article, the tracheid length, proportion of latewood and wood density of black pine indigenous to Greece was investigated based on the sampling of 331 trees, 55 years old and older; the probes were taken only from the 10 outer rings.
Abstract: Geographical location (north/south latitude), social position of trees in a forst stand (dominant, codominant, suppressed) and site quality were investigated as to their effect on tracheid length, proportion of latewood and wood density of black pine indigenous to Greece. Tracheid length was fund greater in the northern location, in dominant trees and at intermediate site qualities. Proportion of latewood was higher in the southern location, in suppressed trees and at intermediate site qualities. Density was higher in the southern location, in codominant trees and at good or intermediate site qualities. Statistically, however, many differences at P = 95 % and all differences at P = 99% are not significant. The present study is based on the sampling of 331 trees, 55 years old and older; the probes were taken only from the 10 outer rings, at breast height. The findings from 6 trees, sampled from pith to bark, present disagreement with the above results.
22 citations
TL;DR: In this paper, NPA was applied in a 2-3 cm band around the middle protion of 2- or 3-year old internodes of three vertically-oriented six-year-old Sugi trees (Cryptomeria japonica D. Don), bringing about abnormal thickening all over the upper segment from the NPA treatment.
Abstract: NPA, applied in a 2–3 cm band around the middle protion of 2- or 3-year-old internodes of three vertically-oriented six-year-old Sugi trees (Cryptomeria japonica D. Don), brought about abnormal thickening all over the upper segment from the NPA treatment. Xylem tissues above and below the treatment, as well as at the treated area itself, was examined by ordinary light microscopy and by scanning electron microscopy. The results obtained seemed to indicate that the tissue formed after treatment in the upper segment of the stem was true compression wood. In the lower segment of the stem, no abnormal tissue but a small amount of latewood-like tissue was produced after treatment.
20 citations
TL;DR: In this paper, the authors derived viscoelastic characteristic functions describing responses to in-plane deformation histories from G11 and G12 (t) determined by strip biaxial stress relaxation testing.
Abstract: Linear viscoelastic properties of laboratory handsheets have been investigated from the two dimensional aspect. According to the linear theory of viscoelasticity, the behavior of transverse isotropic materials such as handsheets subjected to plane stresses is fully described by the two in-plane relaxation functions G11 (t) and G12 (t). In the present paper, some viscoelastic characteristic functions describing responses to in-plane deformation histories are derived from G11 (t) and G12 (t) determined by strip biaxial stress relaxation testing. The predicted uniaxial relaxation function curve was in good agreement with the experimental one, and the viscoelastic Poisson's ratios in uniaxial stress relaxation and in uniaxial constant strain rate extension were decrease functions of time. Effects of beating on the areal dilatation and shear relaxation functions are discussed by introducing the classical concept of relaxation spectrum.
TL;DR: Crystalline inclusions were observed in more than 50%, silica in nearly 20% of about 1500 wood specimens representing ±750 species from 40 genera of the laurel family, with taxonomic implications on the specific, generic and suprageneric level.
Abstract: Crystalline inclusions were observed in more than 50%, silica in nearly 20% of about 1500 wood specimens representing ±750 species from 40 genera of the laurel family. Both types of inorganic cell deposits are described and classified with regard to composition, habit, size, degree of isolation and location. Their diagnostic value and taxonomic implications on the specific, generic and suprageneric level are discussed with respect to intra as well as extrafamiliar relationships.
TL;DR: In this article, the authors measured the acoustic velocities of a wide range of particle boards from measurements of the transit times of wave packets through the materials, and found that the board's skin layer properties are correlated with the properties of the board.
Abstract: The acoustic velocities of a wide range of particle boards were determined from measurements of the transit times of wave packets through the materials. Velocities measured along the plane of the board are dependent on the properties of the board's skin layer, and are reasonably well correlated with the board's modulus of elasticity (r=0.73) and modulus of rupture (r=0.65). Velocities measured perpendicular to the plane of the board are not so well correlated with the mechanical properties of the board — the most significant being the Z strength parameter (r=0.56). The results suggest that this form of non destructive testing would be more suited to production line monitoring than to replacing or complementing existing test methods.
TL;DR: Kraft and ethanol organosolv lignins from Picea abies and Fagus sylvatica were carboxymethylated with bromoacetic acid as discussed by the authors.
Abstract: Kraft and ethanol organosolv lignins from Picea abies and Fagus sylvatica were carboxymethylated with bromoacetic acid. Of the total hydroxyl groups in the lignins, 60–70% were carboxymethylated. The reaction led to an increase of the number-average molecular weights. The moisture adsorption of the carboxymethylated products is about one and a half as high as that of the original lignins. There are no remarkable differences between the solubilities of the treated and untreated products.
TL;DR: In this paper, the reduction in hygroscopicity as spruce wood is impregnated with linseed oil may be accounted for using a molecular exclusion model, which appears to displace 90 water molecules and occupy 6 hydrogen bonding sites in the wood.
Abstract: The reduction in hygroscopicity as spruce wood is impregnated with linseed oil may be accounted for using a molecular exclusion model. On the basis of the model, each linseed oil molecule appears to displace 90 water molecules and occupy 6 hydrogen bonding sites in the wood.
TL;DR: In this article, the longitudinal permeability of Abies grandis wood swollen to varying degree by water vapour sorption has been measured using a non-swelling liquid, and the results obtained show that cell wall swelling causes a reversible decrease in permeability in both air dried and solvent exchange dried specimens.
Abstract: The longitudinal permeability of Abies grandis wood swollen to varying degree by water vapour sorption has been measured using a non-swelling liquid. The results obtained show that cell wall swelling causes a reversible decrease in permeability in both air dried and solvent exchange dried specimens.
TL;DR: In this paper, the separation of unsaponifiable from saponifiable constituents of tall oil fatty acids by different methods has been attempted, and it was shown that after catalytic hydrogenation of the fatty acids it was possible to separate to a great extent the saturated solid acids and the rosin acids present from other components.
Abstract: The separation of unsaponifiable from saponifiable constituents of tall oil fatty acids by different methods has been attempted. After catalytic hydrogenation of the fatty acids it was possible to separate to a great extent the saturated solid acids and the rosin acids present from other components.
TL;DR: In this article, the separation of unsaponifiable from saponifiable constituents of tall oil fatty acids by different methods has been attempted by means of GC, TLC, NMR and UV analyses.
Abstract: SummaryThe separation of unsaponifiable from saponifiable constituents of tall oil fatty acids by different methods has been attempted. After catalytic hydrogenation of the fatty acids it was possible to separate to a great extent the saturated solid acids and the rosin acids present from other components.After separation the different fractions were investigated by means of GC, TLC, NMR and UV analyses. As a result of these measurements it was obvious that the acid-poor fraction consisted of unsaturated acids, several aromatic compounds, partly of phenolic structure and unidentified materials. The concentration of the aromatic compounds was estimated at about 2% by weight. The hydrogenated and filtered fraction was methylated and submitted to a GC/MS analysis. A number of aliphatic and aromatic compounds could be identified.
TL;DR: In this paper, the possibility of demonstrating in the transmission electron microscope components such as copper, chromium and arsenic of preservative salts in the wood cell walls using secondary reactions with chemicals was discussed.
Abstract: The study is concerned with the possibility of demonstrating in the transmission electron microscope components such as copper, chromium and arsenic of preservative salts in the wood cell walls using secondary reactions with chemicals. Among the 18 substances tested only 9 showed a substantial positive effect, which was established on the basis of the electron contrast or depositions obtained within the various wall layers. It is suggested that copper is adsorbed onto the matrix substances of the wood cell wall rather than on cellulose.
TL;DR: Tangential latewood sections (60 μm) of Scots pine sapwood were differently treated with chlorite and subsequently incubated two strains of Bacillus polymyxa caused a weight loss up to about 25%, including a loss of lignin of about 42.
Abstract: Tangential latewood sections (60 μm) of Scots pine sapwood were differently treated with chlorite. The subsequently incubated two strains of Bacillus polymyxa caused a weight loss up to about 25%, including a loss of lignin of about 42%.
TL;DR: In this paper, an extension of Jacobs' method for measuring growth strains is presented, which yields residual strain information at many points in the cross section other than along the diametrical plank.
Abstract: Previous methods for measuring residual longitudinal growth strain distributions in logs are reviewed. An extension is given of Jacobs' method for measuring growth strains which yields residual strain information at many points in the cross section other than along the diametrical plank. Some of the longitudinal growth strain distributions measured using the new method are presented.
TL;DR: In this article, the effects of pulp freezing and thawing and of frozen pulp storage on fibre, wet web, and handsheet properties are discussed, and a variety of radiata pine kraft pulps, a radiata Pine sodium bisulphite pulp, and silver beech and hard beech (Nothofagus species) kraft pulpps are examined.
Abstract: A requirement of long-term research on pulp fibres in that the material for study be stored for prolonged periods without deterioration and without changes in properties. In this paper effects of pulp freezing and thawing and of frozen pulp storage on fibre, wet web, and handsheet properties are discussed. A variety of radiata pine kraft pulps, a radiata pine sodium bisulphite pulp, and silver beech and hard beech (Nothofagus species) kraft pulps are examined.
TL;DR: In this paper, the applicability of a proposed procedure based on accepted, reliable, statistics was evaluated for characterizing the duration of load properties of wood in bending, by subjecting small, clear, wood specimens to several constant stress levels, it was experimentally demonstrated that the proposed procedure is capable of estimating, at an acceptable level of confidence, the maximum service life beyond which a specified proportion of the nominal population will survive.
Abstract: The applicability of a proposed procedure based on accepted, reliable, statistics was evaluated for characterizing the duration of load properties of wood in bending. By subjecting small, clear, wood specimens to several constant stress levels, it was experimentally demonstrated that the proposed procedure is capable of estimating, at an acceptable level of confidence δ the maximum service life beyond which a specified proportion γ of the nominal population will survive. The extension of this procedure to structural sized members seems plausible, since an estimate of the short term ultimate strength for each specimen is not required. Another attribute of the procedure is that parametric estimates can be computed without failing all of the specimens; thus this should significantly reduce the duration of load test time.
TL;DR: In this article, the results of the method must be interpreted with care, as the fluid system selected for use in maximum effective pore radius determinations has too high an interfacial surface tension, and the pressure differential required for the determination can be large enough to cause partial or total pit membrane displacement.
Abstract: With coniferous timbers, if the fluid system selected for use in maximum effective pore radius determinations has too high an interfacial surface tension, the pressure differential required for the determination can be large enough to cause partial or total pit membrane displacement. Under these circumstances, the results of the method must be interpreted with care.
TL;DR: In this article, the cutting forces were measured as a function of applied tool-work electrical potential, and the cutting tool and workpiece were electrically insulated so that there was no current flow.
Abstract: Slow speed wood cutting tests were carried out in which cutting forces were measured as a function of applied tool-work electrical potential. The cutting tool and workpiece were electrically insulated so that there was no current flow. Applied potential had no discernible effect on the cutting forces measured in the cutting of unextracted and extracted wet wood.
TL;DR: In this article, a method for the derivatization of low molecular weight lignin acidolysis product by reduction-acetylation is described, where Borane dimethyl sulfide complex has been used as reducing agent.
Abstract: A method for the derivatization of low molecular weight lignin acidolysis product by reduction-acetylation is described. Borane dimethyl sulfide complex has been used as reducing agent. The derivatives could be analysed by gas chromatography.