Douglas-fir Sapwood Research Articles

Microstructural and Thermo-Mechanical Characterization of Furfurylated Douglas Fir.

Fast-growing wood has become a major source of materials for the wood industry in recent years, but defects have limited its use. Therefore, modification is urgently needed for the more efficient application of wood products. In this study, a 30 to 50% solution of furfuryl alcohol (FA) was impregnated into Douglas fir sapwood. The microstructure and thermal properties of the specimens before and after furfurylation were evaluated by different techniques. The weight percentage gain (WPG) of modified wood increased up to 22.97%, with the polymerized FA distributed in cell lumens and cell walls, as well as chemically bound to wood components. The polyfurfuryl alcohol (PFA) was mainly located in the tracheids, ray parenchyma cells, and resin canals. In addition, the furfurylated cell walls were greatly thickened. Raman spectra showed that modified wood had significant background fluorescence that covered other peaks. Differential Scanning Calorimetry analysis revealed that the cross-linking reaction between FA and wood changed the shape of curves, with no endothermic or exothermic peaks within the programmed temperature. Moreover, Thermogravimetry and Dynamic Mechanical Analysis results both confirmed that the furfurylation increased the thermal stability of Douglas fir. The percentage of the final mass loss of untreated specimen was 80.11%, while the highest one of furfurylated specimen was 78.15%, and it gradually decreased with increasing FA concentration. The storage modulus (E') and loss modulus (E″) of the furfurylated wood were both lower, and the damping factor (tan δ) was higher than the untreated one. When the temperature reaches about 75 °C, the untreated specimen began to soften and deform. At 90 °C, it fractured completely while the furfurylatedone remained stable. This study demonstrated that furfurylation can improve wood properties and elongate its service life.

ABILITY OF NATURAL EXTRACTS TO LIMIT MOLD GROWTH ON DOUGLAS-FIR SAPWOOD

The ability of selected plant extracts from wood and foliage to inhibit mold regrowth on fungal colonized wood was evaluated on Douglas-fir sapwood. Most foliage extracts produced some inhibition of Graphium or Trichoderma species, but isolations of other fungi increased following treatment. Five out of eight wood extracts produced 50% reductions in isolations, and those from Alaska cedar, western juniper, and incense cedar produced at least 80% reductions. The results indicate that wood extracts may be useful for reducing the incidence of mold on wood products, but none of the materials evaluated completely inhibited the test fungi. These extracts may provide a useful value-added application for by-products of lumber production from these species.

An integrated approach using Bacillus subtilis B26 and essential oils to limit fungal discoloration of wood

Bacillus subtilis and essential oils have been explored separately for their ability to limit colonization by wood stain and mold fungi, but neither approach has been completely effective. One alternative strategy would be to combine the bacterial biocontrol with one or more natural products extracts. In this report, the ability of combinations of B. subtilis B26 and 20 essential oils to limit fungal stain was explored on Douglas-fir sapwood wafers under controlled laboratory conditions. A number of extracts markedly improved the anti-fungal activity of B. subtilis B26, including 0.25% myrtlewood oil, 0.5% orange oil, 0.5% lime oil, and 1% Leyland cypress needles oil, which yielded improvements by 2 to 8 times. However, none of the combinations completely protected the wood from fungal attack. The results illustrate the difficulties associated with controlling the diverse array of organisms that can colonize freshly cut wood.

Correlation of carbon isotope ratios in the cellulose and wood extractives of Douglas-fir

Cellulose is usually isolated from the other components of plant material for analysis of carbon stable isotope ratios ( δ 13C). However, many studies have shown a strong correlation between whole-wood and cellulose δ 13C values, prompting debate about the necessity of cellulose extraction for tree-ring studies. The δ 13C values were measured in whole wood, extractive-free wood, purified cellulose, acetone/water-soluble extractives and hot water-soluble extractives of Douglas-fir sapwood. Cellulose and acetone/water-soluble extractives from heartwood from the same trees also were compared. Although the various materials showed different absolute δ 13C values, the components of the same samples, including the extractives, were correlated. The correlations of carbon isotope ratios of cellulose, extractive-free wood and extractives, and the relatively low concentration of the extractives in the wood, suggests that extraction of purified cellulose from Douglas-fir wood samples may not be necessary for some tree-ring analyses.

NMR imaging of fluid pathways during drainage of softwood in a pressure membrane chamber

An experiment was implemented to study fluid flow in a pressure media. This procedure successfully combines nuclear magnetic resonance imaging with a pressure membrane chamber in order to visualize the non-wetting and wetting fluid flows with controlled boundary conditions. A specially designed pressure membrane chamber, made of non-magnetic materials and able to withstand 4 MPa, was designed and built for this purpose. These two techniques were applied to the drainage of Douglas fir sapwood. In the study of the longitudinal flow, narrow drainage fingers are formed in the latewood zones. They follow the longitudinal direction of wood and spread throughout the sample length. These fingers then enlarge in the cross-section plane and coalesce until drainage reaches the whole latewood part. At the end of the experiments, when the drainage of liquid water in latewood is completed, just a few sites of percolation appear in earlywood zones. This difference is a result of the wood anatomical structure, where pits, the apertures that allow the sap to flow between wood cells, are more easily aspirated in earlywood than in latewood.

Cavitation and water storage capacity in bole xylem segments of mature and young Douglas-fir trees

Hydraulic specific conductivity, vulnerability to cavitation and water storage capacity of Douglas-fir sapwood was determined for samples from six young (1.0–1.5 m tall) and six mature trees (41–45 m tall). Measurements on samples from young trees showedthere were no effects of two contrasting sample types (entire stem segments vs sectors chiseled out of entire stems) on any of the calculated hydraulic parameters, for vulnerability to cavitation and water storage capacity. Measurements on mature trees were made on wood from four heights on the bole and from two sapwood depths. Outer and inner sapwood at the base of the tree had higher water storage capacities and were more vulnerable to cavitation than was sapwood from the tree top. At every height, old trees were more vulnerable to cavitation than at 1.0 m from the ground in young trees. The water storage capacities showed three distinct phases at the base of the trunk. Young trees had similar water storage capacity (per unit volume of sapwood) to the topof the mature trees, which was lower than the water storage capacity throughout the rest of the bole xylem. The way in which capacitance was calculated (on a volumetric basis vs a relative water content basis) affected the conclusion one would draw at the low water potentials (<–3 MPa). Within a tree, we found an apparent trade-off between having both hydraulic specific conductivity and stem water storage, and vulnerability to cavitation.

Fungal Colonization of Douglas-Fir Sapwood Lumber

The fungi colonizing Pseudotsuga menziesii (Douglas-fir) sapwood lumber were assessed in sam- ples collected from locations in western Oregon. A total of 547 isolates representing 29 genera and 45 species were obtained from sample boards. Graphium spp. represented 17% of all isolates, and the inci- dence of these species increased with time after saw- ing. The addition of streptomycin to malt extract agar improved isolation frequencies, while the addi- tion of cycloheximide sharply limited isolations to Graphium spp. and some Trichoderma isolates. The results indicate that Douglas-fir sapwood is suscepti- ble to colonization by a variety of fungal species. As a result, control strategies that concentrate on one fungus may have limited success because of interfer-

Fungal colonization of Douglas-fir sapwood lumber

The fungi colonizing Pseudotsuga menziesii (Douglas-fir) sapwood lumber were assessed in samples collected from locations in western Oregon. A total of 547 isolates representing 29 genera and 45 species were obtained from sample boards. Graphium spp. represented 17% of all isolates, and the incidence of these species increased with time after sawing. The addition of streptomycin to malt extract agar improved isolation frequencies, while the addition of cycloheximide sharply limited isolations to Graphium spp. and some Trichoderma isolates. The results indicate that Douglas-fir sapwood is susceptible to colonization by a variety of fungal species. As a result, control strategies that concentrate on one fungus may have limited success because of interference from competing flora.

Steam pretreatment of Douglas-fir wood chips. Can conditions for optimum hemicellulose recovery still provide adequate access for efficient enzymatic hydrolysis?

Douglas-fir sapwood and heartwood were impregnated with SO2 and steam exploded at three severity levels, and the cellulose-rich, water-insoluble component was enzymatically hydrolyzed. The high-severity conditions resulted in near complete solubilization and some degradation of hemicelluloses and a significant improvement in the efficiency of enzymatic digestibility of the cellulose component. At lower severity, some of the hemicellulose remained unhydrolyzed, and the cellulose present in the pretreated solids was not readily hydrolyzed. The medium-severity pretreatment conditions proved to be a good compromise because they improved the enzymatic hydrolyzability of the solids and resulted in the recovery of the majority of hemicellulose in a monomeric form within the water-soluble stream. Sapwood-derived wood chips exhibited a higher susceptibility to both pretreatment and hydrolysis and, on steam explosion, formed smaller particles as compared to heartwood-derived wood chips.

Non-Darcian Air Flow in Wood. Part 2. Nonlinear Flow

Summary In this study, permeability measurements and flow rate-pressure-relationship analysis were carried out to determine whether non-Darcian flow due to nonlinear flow is present during air flow through red oak and red alder heartwood, and ponderosa pine and Douglas-fir sapwood. The results indicated that there was no evidence of nonlinear flow in red alder, ponderosa pine, and Douglas-fir throughout the entire range of flow rates, and for red oak at flow rates below 19.57 cm3/s. At higher flow rates, the results for red oak showed that the superficial specific permeability at the mean pressure of 50kPa decreased with the increase of the flow rates, and the equation relating pressure drop and flow rate at a given mean pressure of 50 kPa involved both a linear and quadratic dependence, thus demonstrating the presence of nonlinear flow components in wood. The calculated Reynolds number that was in the range of 0.263 to 1.05, further suggested that the nonlinear flow found in red oak heartwood at higher flow rates was probably nonlinear laminar flow due to the kinetic-energy losses occurring in the curved openings.

Non-Darcian Air Flow in Wood. Part 3. Molecular Slip Flow

Summary In this study, the detection and evaluation of non-Darcian air flow due to slip flow through four species were carried out. The results indicated that non-Darcian air flow due to slip flow existed in all the specimen groups studied. The true permeability of red oak heartwood, red alder heartwood, ponderosa pine sapwood and Douglas-fir sapwood was 20.91, 7.05, 0.51 and 0.068μ3/μm, respectively. The average ratios of the superficial specific permeability at 50kPa mean pressure to the true permeability were found to be: 1.047 for red oak heartwood; 1.204 for red alder heartwood; 1.292 for ponderosa pine sapwood; and, 1.53 for Douglas-fir sapwood. The slip flow constant b was highest (26.5kPa) for Douglas-fir sapwood, followed by that for ponderosa pine sapwood (14.6 kPa) and red alder heartwood (10.2 kPa), and lowest (2.3kPa) for red oak heartwood. The radius (r) and the number of average effective openings (n) were found to be: 17.432μm and 0.066×106 per cm2 for red oak heartwood; 3.955 μm and 7.5 ×106 percm2 for red alder heartwood; 2.972μm and 3.3 ×106 percm2 for ponderosa pine sapwood; and, 1.552μm and 3.6 ×106 per cm2 for Douglas-fir sapwood respectively.

Douglas-fir polyphenols and heartwood formation

Phenolic extractives have been isolated from Douglas-fir sapwood and heartwood and identified by NMR and mass spectroscopy. Pinocembrin, [5,5′]-bisdihydroquercetin and two lignans, pinoresinol and 2,3-dihydro-2-(4′- O-β-glucopyranosyl-3′-methoxyphenyl)-3-hydroxymethyl-5-(3-hydroxypropyl)-7-methoxy-benzofuran are reported for the first time in these tissues. The chemical structures of these phenolic extractives show that heartwood formation is characterized by both primary (biosynthetic) and secondary reactions. Secondary reactions include hydrolysis of phenol glucosides and oxidative polymerization. © 1997 Elsevier Science Ltd. All rights reserved

Non-Darcian Air Flow in Wood. Part 1. Specimen Length Effect

The longitudinal superficial air permeability of red oak and red alder heartwood, and ponderosa pine and Douglas-fir sapwood at various specimen lengths, was measured with a specially designed apparatus. The results showed that non-Darcian behaviour due to specimen length existed in all tested wood species and types. Furthermore, there was a strong evidence of the existence of a certain specimen length above which permeability remained almost constant. These specimen lengths for the tested species were 140, 100, 60, and 40mm for red oak, red alder, ponderosa pine, and Douglas-fir. respectively. Within these specimen lengths for the respective tested species, permeability increased drastically with decreasing specimen lengths. Therefore, the specimen lengths of 140. 100, 60. and 40mm for red oak heartwood, red alder heartwood, ponderosa pine sapwood, and Douglas-fir sapwood, respectively, will be used for the evaluation of non-Darcian air flow due to other factors such as slip flow and nonlinear flow in a subsequent series of experimental tests.

Surface temperature measurements on burning wood specimens in the Cone Calorimeter and the effect of grain orientation

AbstractSurface temperatures were measured on dry Douglas fir sapwood specimens during Cone Calorimeter tests using thermocouples and an infra‐red pyrometer. Good agreement between the thermocouples and the pyrometer was obtained when (1) the emissivity was assumed to be 1.0 and (2) the thermocouples were in good contact with the surface and were not located in the proximity of a fissure. The major fissures were normal to the grain of the wood and the volatiles vented through the fissures. Char oxidation in the region between the vertical fissures resulted in higher surface temperatures.

Summative Analysis of Nine Common North American Woods

Abstract The summative analysis of lignocellulosic materials has heretofore been a complicated process or the analysis has been incomplete. The Bomb/HPLC summative analysis method presented in this report results in a complete analysis of woody materials using a sample preparation scheme that is easily adopted into a normal laboratory routine. The method relies on HPLC for the majority of the component analyses. To demonstrate the applicability and reproducibility of the Bomb/HPLC method, ten wood samples, from nine different wood species, were analyzed in triplicate and the summative analysis of each sample was effected. The ten woods analyzed were: American beech ( Fagus grandifolia ), Quaking aspen ( Populus tremuloides ), Black cherry ( Prunus serotina ), Sugar (Hard) maple ( Acer saccharum ), Red (Soft) maple ( Acer rubrum ). White ash ( Fraxinus americana ), Yellow birch ( Betula verrucosa ), Douglas fir heartwood and Douglas fir sapwood ( Pseudotsuga menziesii ), and White fir sapwood ( Abies conco...

Ultrasonic, hardness and x-ray densitometric analysis of wood

Ultrasonic, hardness and x-ray densitometric methods were used to predict the wood quality of Douglas fir sapwood from pruned and control trees. Measurements were performed on logs and on increment cores. On logs, hardness was tested by a pilodyn instrument. Longitudinal waves (80 kHz) were used to measure the velocity in the radial anisotropic direction of the wood. Surface waves of the same frequency were employed to measure the velocity on the circumference of the log in the longitudinal anisotropic direction of the wood. On increment cores, 1 MHz waves, longitudinal and transverse, were used to measure the velocity of ultrasonic pulses along three anisotropic axes of the wood, using the through-transmission technique. The predictive power of the pilodyn test and of the surface wave velocity method for logs was judged in relation to several independent variables on cores given by the densitometric method and by ultrasonic velocities and elastic constants of the wood.

Triterpenes from Douglas fir sapwood

The saponified ether-soluble extractives of Douglas fir sapwood contained (24 R)- 4α,14α,24-trimethyl-9β,19-cyclo-5α-cholestan-3β-ol(24 R-cyclocucalanol),a new natural product; 4α,14α-dimethyl-9β,19-cyclo-24-methylene-5α-cholestan-3β- ol (cycloeucalenol); and (24 R)-4α,24-dimethyl-5α-cholest-7-en-3β-ol (24 R- methyllophenol); this is the first time they have been reported from Douglas fir.

Diffusion of dissolved oxygen in liquid-saturated Douglas fir sapwood

A technique was developed for the determination of the effective dissolved oxygen diffusivity in liquid-saturated softwood in a diffusion cell under ambient pressure. From the measurements in the temperature range 2° to 50°C, the activation energy of diffusion was found to be 4.6 kcal/mole. The diffusivity in summerwood is about one half of that in springwood. The diffusivity of dissolved oxygen through composite springwood and summerwood layers was based upon samples of two Douglas fir sapwood blocks saturated with water. In the radial and tangential directions, diffusivity was 1.4 to 2.3x10-6cm2/s, which is about 6 to 10% that of dissolved oxygen diffusivity in water. The diffusivity in the longitudinal direction is about 5.5 times that in the other two directions. The diffusivity of dissolved oxygen through liquor-saturated wood and the effect of delignification on oxygen diffusion were also determined.

Microscopical studies on the peroxide bleaching of Douglas fir wood

The effect of alkaline hydrogen peroxide on Douglas fir sapwood and heartwood was investigated by ultraviolet microscopy and reflectance spectrophotometry. It was found that the high absorbance of the heartwood elements around 300 nm which was attributed to the flavanone dihydroquercetin was readily eliminated by the action of peroxide. It is also proposed that the brightening effect of hydrogen peroxide is due in part to the destruction of coniferaldehyde groups which occurs to the same extent in both sapwood and heartwood and in all the morphological elements. A correlation between the concentration of chromophoric groups and the concentration of lignin is demonstrated.

Some Aspects of Softwood Permeability. I. Structural Studies with Douglas Fir Sapwood and Heartwood

Some Aspects of Softwood Permeability. I. Structural Studies with Douglas Fir Sapwood and Heartwood