Showing papers in "Wood Science and Technology in 2001"

Surface characterization of esterified cellulosic fibers by XPS and FTIR Spectroscopy

Abstract: X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy techniques were used to study the surface chemical compositions of cellulosic fibers before and after treatments. The fibers were treated with phthalic anhydride and maleated polypropylene for surface modifications. Both XPS and FTIR spectroscopy analysis indicated that chemical bonds between hydroxyl groups of cellulosic fibers and anhydride moieties of phthalic anhydride and maleated polypropylene have occurred through esterification reaction. These chemical reagents have been added to the surface of cellulosic fibers in the form of monoester, i.e., the formation of esterified cellulosic fibers bearing a pendent carboxylic group.

Oxidation of hardwood kraft-lignin to phenolic derivatives with oxygen as oxidant

Abstract: A hardwood kraft lignin was oxidized in alkaline medium to obtain phenolic compounds (syringaldehyde, vanillin and its acids). To avoid lignin condensation, the lignin was precipitated from a black liquor with a calcium salt dissolved in a water soluble alcohol. Oxygen was the oxidant employed, and copper (II) and cobalt (II) salts were used as catalysts. Effect of temperature, reaction time, oxygen pressure, alkali concentration and catalyst on yield and product distribution were studied. In all the range of variables lignin conversion and aldehyde yield remains low and the more important effect on aldehyde yield was due to the alkali concentration, which must be fixed at about 2 N. The precipitation method did not significantly increase the aldehyde yield, in contrast with the results of nitrobenzene and CuO oxidations. In catalyzed oxidations, no increase in phenolic aldehydes was observed and, with some catalyst, the conversion into phenolic derivatives was reduced. Lignin conversion into low molecular weight products is responsible for the low phenolic product yield and the type of catalyst could lead the oxidation into phenolic products or into low molecular weight acids.

Differences in wood properties between juvenile wood and mature wood in 10 species grown in China

Abstract: This study examined the intrinsic differences in various wood properties between juvenile wood and mature wood in 10 major reforestation species in China. Comparisons between juvenile wood and mature wood were made in both plantation- and naturally-grown trees. Considerable differences in most wood properties were found both between plantation-grown juvenile wood and mature wood, and between naturally-grown juvenile wood and mature wood. This suggests that wood properties of plantation-grown trees, to a large extent, depends on their juvenile wood contents, and can thus be manipulated effectively through rotation age. In general, the longer the rotation age, the lower the juvenile wood content, and the stronger the mechanical properties of the plantation-grown woods. However, the differences between juvenile wood and mature wood vary with wood properties and species. In general, juvenile wood and mature wood have less difference in chemical composition than in anatomical and physico-mechanical properties. Compared to the softwoods studied, the hardwoods appear to have less difference between juvenile wood and mature wood.

Characterisation of juvenile wood in teak

Abstract: Juvenile wood properties are studied in a ring-porous tropical hardwood – teak (Tectona grandis L. F), to assess the utilisation potential of short rotation timber. Compared to mature wood, it is characterised by wide rings, short fibres, small diameter, low vessel percentage, high cell wall, wide microfibrillar angle and relatively low or almost similar mechanical properties. While the average modulus of elasticity and modulus of rupture in juvenile wood are 85% and 82% respectively of the mature wood value, the longitudinal compression strength is similar. With relatively small fibrillar angle of 15° and the scope for genetic selection of individual trees, teak juvenile wood has potential for desired dimensional stability. The segmented regression models and visual interpretation of radial patterns of variation in anatomical properties reveal that juvenility in plantation grown teak extends up to 15, 20–25 years depending on the property, growth rate and individual tree and plantation site. The fitted regression models, to explain the age-related variations in juvenile wood properties range from simple, linear to exponential, reciprocal and quadratic equations. Fibre length, microfibrillar angle, vessel diameter/percentage and ring width appear to be the best anatomical indicators of age demarcation between juvenile and mature wood, although maturation age often varies among the properties. The projected figures for proportion of juvenile wood in plantation grown teak at breast height are 80–100% and 25% at ages 20 and 60 years respectively.

A model of anisotropic swelling and shrinking process of wood

Abstract: To elucidate the origin of the shrinking anisotropy of wood during the drying process, as well as to begin to gain an understanding of the interaction between the moisture and the cell wall components, the shrinking process of a single wood fiber regarding water desorption was simulated by using an analytical model which was developed in the previous report (Part 1). Resulting data were compared with the experimental ones in this paper. The following conclusions were obtained: (1) The matrix substance, as a skeleton in the secondary wall, tends to shrink isotropically. However, the cellulose microfibrils, as a rigid framework of the cell wall, almost did not shrink at all due to the water desorption. As result, wood shrinks anisotropically during a drying process. The microfibril angle in the S2 layer is one of the most important factors related to the degree of shrinking anisotropy of the wood while drying. (2) According to the simulation, the expansive strain caused in the matrix skeleton by the water sorption increases by 15% (= 150,000 micro-strains) from the oven-dried condition to the green condition. Based on this value, the moisture content at the fiber saturation point is calculated to be about 35%, which is close to the experimentally obtained one. These results give quantitative evidences that the hygroexpansion of the wood cell wall is controlled by the mechanism of the reinforced matrix hypothesis.

Hydrophobization of wood surfaces: covalent grafting of silicone polymers

Abstract: The hydrophilicity of Maritime pine wood surfaces was modified by silicone, an extremely hydrophobic material. A generic method for the introduction of a variety of silicones at the surface of pre-treated wood was developed. The initial treatment of wood with maleic anhydride and allyl glycidyl ether resulted in oligoesterified wood bearing terminal alkenes. The hydro- osilylation of these groups, performed with hydride-terminated silicones, led to very hydrophobic surfaces, even after extensive soxhlet extraction with good solvents for silicones. Thze presence of silicon, only at the surface of hydrosilylated wood, was confirmed by ESCA. The silicones appear to be attached to the wood by covalent bonds.

Natural factors affecting wood structure

Abstract: The structure and properties of wood are affected by genetic, environmental and anthropogenic factors acting during the formation of wood cells and tissue. In order to understand these factors and the way they interact, wood scientists face exciting and challenging problems in two areas of plant biology. Firstly, they need to understand the molecular basis for genetic programs which code for various fundamental processes of xylogenesis. The most promising area seems to lie in the identification of genetic programs for seasonal initiation and termination of cambial activity. Secondly, they need to understand the basic code, the mechanism of propagation and the transduction system of morphogenetic messages which provide information for structural differentiation of xylem in the plant. This paper discusses the various concepts concerning the contribution of auxin to the morphogenetic fields in which the information is specified without spatial, directional or time-limiting conditions.

Investigation of relationships between cell and pulp properties in Eucalyptus by examination of within-tree property variations

Abstract: Relationships between cell and pulp properties were investigated by examining the within-tree property variations in Eucalyptus camaldulensis and Eucalyptus globulus. Properties investigated included proportions of ray and axial parenchyma, thickness of cell walls and cell wall percentages. The characteristics of the ray and axial parenchyma (their proportions and wall thickness) were found to have a significant influence on all measured pulp properties, including paper strength properties. Multiple regression of pulp properties in relation to cell properties revealed that nearly all measured pulp properties were explained by cell properties at the 1% significance level. It was concluded, therefore, that all cell types are important for predicting pulp properties, and it is strongly recommended that tree breeding programs for Eucalyptus include the measurement of all cell types.

Batch measurements of wood density on intact or prepared drill cores using x-ray microdensitometry

Abstract: The performance of a batch scanning x-ray densitometer for measuring wood density without sample preparation, i.e., on intact drill cores, or on rectangular samples prepared from drill cores, was analysed. Effects of x-ray intensity, sample thickness and fiber direction, as well as extractives content, were evaluated for young (mainly sapwood) and old (mainly heartwood) wood from Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.). The x-ray power level used as standard (1.4 kW; 40 kV and 35 mA) seemed appropriate for the tested species and specimen thickness. The density of intact drill cores could be determined with a mean standard deviation of 1.6% for each sample, with a single machine run, if the cores were mounted with a fixed fiber direction and calibrations were made for each wood type. The corresponding precision for rectangular samples was 1.0%. Further improvements are attainable by using standard reference samples in each machine run and batch-wise analysis. For the chosen wood types and measurement technique, a sample thickness of 5 mm should give the best precision. However, for species with very narrow rings, thinner samples would improve the spatial resolution when ring boundaries are angled or curved. Extractives should be removed, especially for pine, but possibly also for spruce, if high precision in density determination is required.

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties I: basic density

Abstract: A non-destructive sampling strategy for basic density, based on removing 12 mm bark-to-bark cores, was developed in E. globulus and E. nitens. Fifty trees of each species, aged 5 to 9 years, were sampled across a range of sites. Core samples were removed on both a north-south and an east-west axis from 6 fixed heights in the base of the tree (0.5 m, 0.7 m, …, 1.5 m). Whole-tree values were calculated from disc samples removed at eight percentage heights (0, 10, 20, …, 70%) and correlations between the cores and whole-tree values were used to determine the optimal sampling height. Core samples were found to be reliable predictors of whole-tree density, explaining between 84% and 89% of the variation between trees. Core sampling of E. globulus and E. nitens to estimate basic density of whole-trees and stands is feasible; cores from trees at all E. globulus sites gave high correlations with whole-tree values. For E. nitens, site differences were apparent, and it is recommended that a small destructive sampling program should be undertaken prior to commencing a major sampling program. Recommended optimal sampling heights are 1.1 m for E. globulus and 0.7 m for E. nitens. Core orientation was not important and density was not related to tree size. Six whole-tree samples or eight core samples are required for estimating the mean density of a stand at a specific site to an accuracy of ±20 kg m−3 with a 95% confidence interval.

An improved fibril angle measurement method for wood fibres

Abstract: A rapid, reliable technique for the observation and measurement of the fibril angle in wood cell walls has been developed. Sonication in the presence of solutions of certain cobalt and copper salts (5%, wt/vol) was found to be most effective in facilitating fibril angle visualisation. Latewood fibre fibril angle, which previously had been difficult to measure, was also visible, though less frequently. This method has been successfully applied to a number of softwood species including coastal Douglas-fir whose prominent spiral thickenings make it difficult to determine the fibril angle by other methods. The method was also used to determine the fibril angle of some hardwood species as well as a non-woody material, flax straw. It can also be used to determine the microfibril angle of pulp fibres although this procedure is less convenient than with wood sections.

Prediction of basic wood properties for Norway spruce. Interpretation of Near Infrared Spectroscopy data using partial least squares regression

Abstract: This work was undertaken to investigate the feasibility of using near infrared spectroscopy (NIR) and partial least squares regression (PLS) as a tool to characterize the basic wood properties of Norway Spruce (Picea abies (L.) Karst.). The wood samples originated from a trial located in the province of Vasterbotten in Sweden. In this trial, the effects of birch shelterwoods (Betula pendula Roth) of different densities on growth and yield in Norway spruce understorey were examined. All Norway spruce trees in each shelterwood treatment were divided into three growth rate classes based on diameter at breast height (1.3 m) over bark. Five discs were cut from each tree (i.e. from the root stem, and at 20%, 40%, 60%, and 80% of the total height). The discs from 40% tree height were used (i.e., where the largest variations in annual ring widths and wood density were found). A total of 27 discs were selected. The discs were used for measuring annual ring widths, wood density, average fiber length and the fiber length distributions. Milled wood samples prepared from the discs were used for recording NIR spectra. PLS regression was used to generate prediction models for the wood properties (Y-matrix) and NIR spectra (X-matrix) as well as between the wood properties (Y-matrix) and the fiber length distributions (X-matrix). One set of models was generated using untreated spectra and fiber length distributions. For a second set of models the structure in the X-matrix, which was orthogonal to the matrix described by the wood properties, was eliminated using a soft target rotation technique called orthogonal signal correction (OSC). The PLS model obtained using “raw” untreated NIR spectra and fiber length distributions had a poor modeling power as evidenced by the cumulative Q2 values. For the PLS models based on untreated NIR spectra the cumulative Q2 values ranged from a minimum of 16% (wood density) to a maximum of 46% (no. of annual rings). Orthogonal signal correction of the X-matrix (NIR spectra or fiber length distributions) gave PLS models with a modeling power corresponding to cumulative Q2 values well in excess of 70%. The improvement in predictive ability accomplished by the OSC procedure was verified by placing four of the 27 observations in an external test set and comparing RMSEP values for the test set observations without OSC and with OSC.

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties III: predicted pulp yield using near infrared reflectance analysis

Abstract: Within-tree variation in kraft pulp yield, predicted using near infrared reflectance analysis, was studied in thirty trees of E. globulus and fifty trees of E. nitens to develop a non-destructive sampling strategy. Trees, aged 5 to 9 years, were sampled across a range of sites in southern Australia. Simulated core samples were removed at six fixed heights easily accessible from the ground (0.5, 0.7, ... 1.5 m) and at seven percentage heights (0, 20, 30, ... 70%). Whole-tree values, calculated from percentage height data, were correlated with the core data to determine the optimal sampling height. Core samples were found to be good predictors of whole-tree pulp yield for E. globulus, with simulated cores taken from the recommended sampling height (1.1 m) explaining more than 50% of variation in whole-tree pulp yield. Results for E. nitens were variable with large site differences apparent. On high quality sites, core samples from the recommended sampling height (0.9 m) were good predictors of whole-tree pulp yield, explaining around 60% of the variation. On poor quality sites, cores were poor predictors of whole-tree pulp yield. Radial orientation of cores was not important and predicted pulp yield was not related to tree size, basic density or fibre length. To estimate stand mean pulp yield to an accuracy of ±1% would require sampling 6 trees of E. globulus and 4 trees for E. nitens using either multiple discs or core samples. A single sampling height (1.1 m) is recommended for sampling for basic density, fibre length, fibre coarseness and predicted pulp yield in E. globulus. For E. nitens the recommended sampling height for basic density and fibre length is 0.7 m and 0.9 m is recommended for predicted pulp yield on good quality sites.

The chemistry of chromated copper arsenate II. Preservative-wood interactions

Abstract: The reactions which cause chromated copper arsenate preservative to fix strongly into wood are reviewed. A number of the mechanisms proposed in the literature appear chemically implausible. A new model is advanced in which the final fixation products are dominated by chromium (III) arsenate, chromium (III) hydroxide, and copper (II)- wood carboxylate complexes. Carboxylate groups should be generated in large numbers in the reduction of chromium (VI) by primary alcohol groups in lignin and carbohydrate fractions, or in the oxidative degradation of lignin. The model is supported by a recent X-ray absorption fine structure analysis.

Axially loaded glued-in hardwood dowels

Abstract: The failure load of axially loaded hardwood dowels glued-in parallel to the grain direction of the jointed timber parts is considered. Two simple theoretical solutions using linear elastic fracture mechanics/ideal plasticity and linear elastic stress analysis, taking into account the finite shear stiffness of the bond line are, presented and compared with experimental results. Theory shows that bond line shear strength is the governing strength property for ductile joints and fracture energy is the governing strength property for brittle joints. Bond line shear strength and fracture energy are determined by means of curve-fitting.

Degradation of lipophilic wood extractive constituents in Pinus sylvestris by the white-rot fungi Bjerkandera sp. and Trametes versicolor

Abstract: The white-rot fungi Trametes versicolor and Bjerkandera spp. are among the most frequent decomposers of angiosperm wood in forest ecosystems and in wood products in service. Wood extractives have a major impact on wood properties and wood utilization. This work evaluated the ability of two white-rot fungal strains (Bjerkandera sp. strain BOS55 and T. versicolor strain LaVec94-6) to degrade the main lipophilic extractive constituents in Scots pine (Pinus sylvestris L.). The time course of wood decay and wood extractive degradation was monitored in stationary batch assays incubated for eight weeks. The strains tested eliminated high levels of total resin, 34 to 51% in two weeks. Wood triglycerides were the most readily degraded extractive components (over 93% elimination in only two weeks). Free fatty acids and resin acids, which are potential fungal inhibitors, were also rapidly decomposed by the fungal strains. Sterols were used more slowly, nonetheless, the fungal degradation of this extractive fraction ranged from 50 to 88% after four weeks.

Removal of Cr(VI) from aqueous solutions by larch bark.

Abstract: The ability of larch (Larix leptolepis Gold.) bark to remove Cr(VI) from dilute aqueous solutions was investigated. The research parameters included the solution pH, contact time, temperature and initial concentration of Cr(VI) in solution. Of the parameters studied, the solution pH was found to be the most crucial. The Cr(VI) removal decreased steadily throughout the pH range studied (pH 2–6), while the Cr adsorption peaked at pH 3. Because the chemical reduction of Cr(VI) to trivalent state occurred to lesser extents even in strong acidic media, the Cr(VI) removal was mainly governed by physico-chemical adsorption. The positive value of the heat adsorption (ΔH 0) indicates the endothermic nature of the Cr(VI) adsorption. The relatively slow rate and irreversible nature of the adsorption as well as the order of the magnitude of the heat adsorption value suggest that the adsorption is of a chemical type. The adsorption data obtained from the equilibrium experiments were well fitted to both the Langmuir and Freundlich isotherms.

TGA modeling of the thermal decomposition of CCA treated lumber waste

Abstract: To guide the development of thermal decomposition methods for disposal of CCA treated wood, reactions during the thermal decomposition of CCA treated wood were modeled using thermogravimetric analysis (TGA), with special focus placed on arsenic volatilization. Simple inorganic compounds, such as As2O5, CuO, and Cr2O3, were used to model the thermal behavior of the inorganics in CCA treated wood. In air and nitrogen, arsenic (V) oxide began to volatilize at 600 °C during temperature ramps at 5 °C/min. During a 5 °C/min ramp in a hydrogen mix, arsenic (V) oxide began decomposition at 425 °C. Arsenic volatile loss from CCA treated wood can depend strongly on the gases produced by wood thermal decomposition. In the presence of As2O5, chromium (III) oxide and copper (II) oxide formed arsenates in air and nitrogen. Chromium arsenates began decomposition as low as 790 °C. This suggested that chromium arsenates in CCA treated wood formed during original preservative fixation may decompose as low as 790 °C. Copper arsenates were stable up to 900 °C in air, but showed only a limited range of stability in nitrogen. Depending on process conditions, the formation of copper arsenates may limit arsenic loss during thermal decomposition of CCA treated wood up to 900 °C. The thermal decomposition of inorganic oxides was influenced by interactions with wood and wood decomposition products. In a dry YP sawdust/As2O5 mix, arsenic (V) oxide volatilized at 370 °C during inert pyrolysis at 5 °C/min and at 320 °C during smoldering combustion at 5 °C/min. Thermal dwells of a dry YP/As2O5 mix showed no arsenic loss at 250 °C, but significant loss occurred during higher temperature dwells. During inert pyrolysis at 5 °C/min, the formation of complexes and hydrates were shown to prevent arsenic loss up to 400 °C.

A three-dimensional paradigm of fiber orientation in timber

Abstract: Knowledge of the three-dimensional orthogonal directions of wood material at any position within a tree is necessary for the understanding of strength reducing effects of knots and essential for the continuation of research in areas which relate small clear wood specimen behavior to the behavior of full size structural timber. A complete three-dimensional paradigm describing the geometry of knots and related fiber distortion, initially derived to predict the strength-reducing behavior of knots in structural timber of Norway Spruce with the finite element method, is presented in this article. Besides strength prediction analyses, it is believed that the paradigm may be useful in other areas of research on structural timber that are effected by fiber orientation, such as drying and form change of structural timber. The paradigm generates fiber orientation in any position within a log or lumber from assumed fiber patterns in planes parallel to the longitudinal direction of the original tree. Fiber patterns in the radial and tangential directions are derived from physical restraints related to fiber production within the annual increase surfaces of the tree and from theories of knot formation. The adaptability of the paradigm allows practically any softwood knot to be modeled with an accuracy that is limited only by input-data. The knot-axis may be non-linear, and the knot cross-section oval with its vertical and horizontal axis increasing from the pith of the stem at chosen rates. Spiral grain may also be included in the paradigm and vary with the annual growth layers. Investigations presented in this article showed that generated fiber orientations for Picea abies complied well with measured fiber distortions, and that the general trends of fiber orientation, explained by the applied knot formation theory, is reflected in the measured specimens.

The use of an acoustic technique to assess wood decay in laboratory soil-bed tests

Abstract: This study assesses the changes in elastic behaviour (i.e. modulus of elasticity – MOE) and mass loss of different hardwood and softwood species exposed to decay in laboratory soil-bed tests. Elasticity moduli were determined using conventional static methods as well as a dynamic method based on flexural vibration. The results obtained show a high correlation between dynamic and static bending measurements for all the timber species tested at different stages of fungal decay. Furthermore, the non-destructive MOE assessment proved to be a good tool for the early detection of wood decay.

Nondestructive sampling of Eucalyptus globulus and E. nitens for wood properties; II. Fibre length and coarseness

Abstract: Within-tree variation in fibre length and coarseness was studied in fifty trees of E. globulus and E. nitens to develop a non-destructive sampling strategy. Trees, aged 5 to 9 years, were sampled across a range of sites in southern Australia. Simulated core samples were removed at six fixed heights easily accessible from the ground (0.5, 0.7, ... 1.5 m) and at eight percentage heights (0, 10, 20, ... 70%). Whole-tree values, calculated from percentage height data, were correlated with the core data to determine the optimal sampling height. Core samples were found to be reliable predictors of whole-tree fibre length, but results were variable for fibre coarseness. Simulated cores taken from the recommended sampling heights explained 87% and 71% of variation in whole-tree fibre length for E. globulus and E. nitens respectively and 54% and 45% of the variation in whole-tree fibre coarseness. Fibre length at all fixed heights showed good correlations with whole-tree values at all sites for E. globulus. For E. nitens the correlations were slightly lower and variable across sites. Results for fibre coarseness varied across sampling heights and sites for both species. The recommended sampling height for fibre length is 1.5 m for both species, whilst for fibre coarseness, the recommended sampling heights are 0.9 and 1.1 m for E. globulus, and 0.9 and 1.3 m for E. nitens. Radial orientation of cores was not important and neither fibre length nor coarseness were related to tree size or basic density. To estimate stand mean fibre length to an accuracy of ±5% would require sampling 9 whole trees or taking cores from 13 trees for E. globulus and 4 whole trees or cores from 8 trees for E. nitens. For estimating stand mean fibre coarseness, 10 whole trees of E. globulus and 7 whole trees are needed for E. nitens. Core sampling for stand mean coarseness would require more trees: 13 to 21 for E. globulus and 11 to 16 trees for E. nitens.

ESR studies of radicals generated by ultrasonic irradiation of lignin solution. An application of the spin trapping method

Abstract: An electron spin resonance (ESR) method combined with a spin trapping reagent was successfully applied to trap and characterize unstable radicals which were generated by ultrasonic irradiation of dimethylsulfoxide (DMSO) solution of hardwood, Fagus crenata lignin. It was found, consequently, that a secondary carbon radical, ∼CH· was trapped as the nitroxide spin adduct when the DMSO solution was subjected to ultrasonic irradiation in the presence of a spin trapping reagent: 2, 4, 6-tri-tert-butylnitrosobenzene (BNB) at 50 °C for 60 minutes under vacuum. This means that the alkyl phenyl ether bonds known as lignin linkage bonds were homolytically scissoned by the ultrasonic irradiation, although the phenoxy radical, Ph-O· as the counter radical of the secondary carbon radical was not trapped by the BNB spin trap. Further, the data showed that the primary carbon radical, ∼OCH2 · is trapped by the BNB to form the corresponding spin adduct, indicating that the hydrogen abstraction from the ortho methoxy group in the syringyl and/or guaiacyl moiety is induced by the secondary carbon radical when irradiated. Based on these findings it was concluded that the Ph-O· radicals produced by the homolytic rupture of the alkyl phenyl ether bonds were not trapped by the BNB spin trap. This suggests that large steric hindrances operate between the syringyl with two methoxy moieties and/or guaiacyl with a methoxy moiety at the ortho position, and the BNB molecule bearing two bulky ortho tert-butyl groups.

Towards a model predicting cutting forces and surface quality in routing layered boards

Abstract: The general aim of work reported here was to assist designers and operators of routers and similar tools for cutting wood-composite boards, by providing a model predicting cutting force components from readily available material properties. This initial study explored, for edge cutting, the variation within a single medium density fibre board across the thickness and in various cutting directions in the plane of the board. Material properties of interest were specific gravity and friction coefficient. In slow linear cutting on a modified milling machine, carbide router inserts cut the edges of layers cut from a medium density fibre board. Specific gravity and coefficient of sliding friction were measured for each layer. Cuts were also made on full-thickness edges in various directions in the plane of the board. Chip thickness was varied from 0.025 to 0.8 mm. Parallel and normal force data and digital video images of chip formation were stored for analysis. Specific gravity increased as the fourth power of the distance from the central plane to the surface. Friction coefficient values, estimated both from cutting forces and from rubbing forces during return, varied about a value of 0.23, with no significant difference between layers. The values for cutting force per mm width of cut increased progressively from the central plane to the surface, in a logarithmic relation with specific gravity. The cutting forces did not vary with cutting direction in the plane of the board. For a sharp edge with 32° rake angle cutting at chip thickness values above 0.1 mm, the normal force component was negative, indicating reduced feed force and improved surface quality. With dulling, the threshold value of chip thickness for this increased. It is concluded that elaboration of this approach would generate relationships suitable for incorporating in a useful general model. However, it may be found that weight per unit area of board will suffice as a proxy for cutting resistance in modelling the cutting of full-thickness edges.

The Potential of Oil and Sago Palm Trunk Wastes as Carbohydrate Resources

Abstract: The carbohydrates content of the water soluble and water insoluble material of the oil and sago palm trunk waste were analysed. The sago palm trunk waste yielded higher water soluble content (17.4%) compared to the parenchymatous tissues and fibers of the oil palm trunk waste i.e. 3.3% and 5.4%, respectively, with less than 10% of neutral carbohydrates detected by cysteine sulphuric assay. However, hot water solubles of the sago palm trunk contained about 61.7% glucose. On the other hand, the acid hydrolysable carbohydrates of the water insoluble materials of both oil and sago palm trunk waste were found to be less than 50% of the total materials. The fibers and parenchyma of the oil palm trunk yielded only 31.9% and 23.6% hydrolysable sugars, respectively. Glucose was the major monosaccharide afforded by all samples of oil and sago palm waste.

Supercritical fluid impregnation of selected wood species with tebuconazole

Abstract: The effects of pressure and temperature on supercritical fluid impregnation of tebuconazole were evaluated on Douglas-fir, western red cedar, red alder, white spruce, and white oak. Higher pressure markedly enhanced both the retention and distribution of tebuconazole in these species. When the rate of pressure release was altered at the ends of treatments of Douglas-fir, results varied. Generally, a higher rate of venting increased the steepness of the preservative gradient inward from the surface. Elevated pressures also affected some wood properties. Western red cedar and white spruce showed collapse, while the other three species were free of such defects. Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) tended to decline with higher pressure in western red cedar and white spruce, but the differences were rarely significant. No significant changes in MOE/MOR occurred with the other 3 species.

Application of cure-accelerated phenol-formaldehyde (PF) adhesives for three-layer medium density fiberboard (MDF) manufacture

Abstract: This study was conducted to optimize hot pressing time and adhesive content for the manufacture of three-layer medium density fiberboard (MDF) through the cure acceleration of phenol-formaldehyde (PF) adhesives by adding three carbonates (propylene carbonate, sodium carbonate, and potassium carbonate) in the core layer. Carbonate type, carbonate level, PF resin content, and hot pressing time were evaluated on the basis of the performance of MDF panels prepared. The application of cure-accelerated PF adhesives by the addition of propylene carbonate reduced both PF resin content and total hot pressing time by 38% and 29%, respectively, for the manufacture of quality three-layer MDF panels (19.1 mm thickness) under the hot-pressing temperature of 205 °C. The optimum concentration of propylene carbonate for cure acceleration of PF resin was found to be 3 wt% by weight based on the resin solids. Bending properties, on one hand, were independent of carbonate type and level, and complied with the minimum requirements by ANSI. Internal bond (IB) strength, on the other hand, was closely related with carbonate types and level used.

Silylation of solid beech wood

Abstract: This report presents a new derivative from the chemical conversion of hardwood. Silylation of hardwood was successfully achieved using trimethylsilyl chloride with pyridine as base. The new wood compounds were analyzed by FTIR spectroscopy. The FTIR spectra of the silylated wood compounds show new absorption bands derived from trimethylsilyl ether groups. Furthermore, the products were investigated by means of EDX analysis. The presence of silicon confirmed the conversion of wood into the corresponding silyl ether derivative. Electron microscopy, i. e. SEM, shows that the location of the silicon was not restricted to the surface of the wood fibres. Penetration of the reactants into the wood body occurred, when a solid wood sample (beads) was used.

Numerical and experimental analysis of a wood drying process

Abstract: Experimental investigation and computational analysis were performed to evaluate the influence of the ambient air parameters during the drying process on the temperature, moisture and resulting deformations and stresses in wood samples. The numerical procedure uses the Finite Volume Method to discretise the equations governing heat, mass and momentum balance and takes into account the anisotropic nature of wood. The comparison of the numerical and experimental results shows very good agreements, implying that the proposed numerical algorithm can be used as a useful tool in designing wood drying schedules.

The effects of maturity and growth rate on the properties of spruce wood tracheids

Abstract: Hypotheses are created regarding the control of size scale and geometry of softwood tracheids within a genotype, and tested using two independent Norway Spruce (Picea abies) materials. Variation in physical dimensions of tracheids is controlled predominantly by cambium maturity. The accumulated amount of production appears to be a somewhat better descriptor of cambium maturity than cambium age. Thus, the mean tracheid dimensions within an annual ring can be predicted on the basis of the distance from the pith of the tree, at least as well as using the number of the annual ring. Cross-sectional tracheid geometry appears to be controlled by the growth rate of the tree.

Nondestructive evaluation of veneer quality using acoustic wave measurements

Abstract: Two nondestructive evaluation methods, impact-induced stress wave techniques and ultrasonics, were investigated to detect lathe checks and knots in veneer, which were identified as key veneer quality properties for some engineered applications. Measurements included wave velocity and attenuation in the directions parallel and perpendicular to the grain. The results showed that both techniques were sensitive to lathe checks when using wave propagation perpendicular to grain. For wave transmission parallel to grain, signals showed some sensitivity to knots. There was no significant difference in wave velocity measurements between stress wave and ultrasonic techniques. Regression models based on stress wave velocities in these two orthogonal directions were developed to estimate the veneer quality index giving a coefficient of determination ranging between 0.39 and 0.50.