An experiment was conducted on commercially heat-treated (HT) Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies [L.] Karst.) sapwood collected from Ht Wood AB, Arvidsjaur, Sweden. Secondary treatment on HT wood was performed in laboratory scale by impregnating with water-repellent preservatives (a commercial one and pine tar) to evaluate their retention and different moisture-related properties. Preservative solutions were impregnated using a simple and effective method. Wood samples were heated at 170°C in a dry oven and were immediately immersed in preservative solutions. Considerable retention was observed in HT wood, particularly in pine. Moisture adsorption properties were measured after conditioning in a high-humidity environmental chamber (4°C and 84% RH). Experimental results showed that secondary treatment enhanced moisture excluding efficiencies by decreasing equilibrium moisture content, suggesting better hydrophobicity. Soaking test in water showed that antiswelling and water repellence efficiencies improved, especially in tar-treated wood. In addition, this type of treatment significantly decreased water absorption. It was also possible to decrease volumetric swellings. Thus, secondary treatment of HT wood with preservative, in particular with tar, improved dimensional stability and water repellency.

This is a summary of a study carried out in Chile to certify industrial kiln drying of radiata pine to comply with the international phytosanitary standard ISPM 15. The drying tests were performed in 100-m3 industrial kilns located at four different sawmills of the VIII region in Chile. The objective was to develop a standard protocol to certify industrial drying of radiata pine depending on the drying schedule and wood thickness. In part, the results were used to develop a multiple regression equation that permits sawmills to select their drying schedules in such a way that the lumber can be officially stamped as both kiln-dried and heat-treated for international trade.

In this work, a numerical stochastic model is used to compare three possible sorting strategies in radio frequency vacuum (RFV) drying of thick timbers, namely, moisture content based pre-sorting (MCPS), batch dry/sort/redrying (b-DSRD) and continuous or retro-feed dry/sort/redry (c-DSRD). The model parameters were calibrated with experimental data of western hemlock dried in a commercial RFV dryer, and the results of the simulations were compared to a single pass base case (SPBC). The numerical results clearly demonstrated the differences among these strategies. The MCPS showed no significant improvement in final timber quality as defined by average timber moisture content, but there is an evident improvement in both b-DSRD and c-DSRD. The comparison was based on the increment of the percent of the on-grade wood (within moisture content range) and the reduction of overdried and underdried (wets) percentages. Furthermore, it was also shown that the effective drying time is roughly independent of the drying strategy

The radial moisture diffusion coefficient in Fick's law for a sample of Norway spruce (Picea abies) under isothermal drying conditions was determined in a parameterization of Arrhenius' equation type. Using X-ray CT-scanning, the wood density and moisture content distributions were obtained in the radial direction for the wood sample. An optimization scheme, based on finite element computation, was then applied to find the parameter values such that the difference between observed and computed moisture content was minimized. The combined numerical and experimental technique was developed to reduce known disadvantages of similar approaches, and a specific algorithm to determine diffusion coefficients was presented. A comparison of the calibrated diffusion coefficient with those given in the literature showed a good fit. The computed moisture content based on the obtained diffusion coefficient and the observed moisture content agreed well. Finally, the effect of measurement errors on the computed material parameter was found to be small

To improve the properties of paper sheets, microfibrillated cellulose (MFC) was isolated from bleached bagasse pulp pretreated with xylanase enzymes and returned to the pulp in varying amounts. The standard hand sheet paper-making method was used. The effect of adding different amounts of MFC on tensile strength (wet and dry), tear resistance, burst strength, opacity, and porosity of paper sheets was studied. Adding MFC to bagasse pulp improved wet and dry tensile strength, but tear resistance and burst strength decreased with increasing amounts of MFC. Also, adding MFC to bagasse pulp did not significantly affect opacity, slightly decreased porosity, and tightened the texture of the paper sheets as observed from scanning electron microscopy images. The strength properties of paper sheets made from bagasse and MFC were compared with those of paper sheets made from bagasse and softwood fibers. Paper sheets containing MFC had higher tensile strength (wet and dry) than those containing softwood fibers, but the later had higher tear resistance and burst strength.

Nanofibers were isolated from bagasse pulp pretreated with dilute hydrochloric acid, dilute sodium hydroxide, cellulase, or xylanase enzymes using high-shear ultrafine grinding and high-pressure homogenization. The effect of the different pretreatments on chemical composition and structure of isolated nanofibers was studied using chemical analyses, X-ray diffraction, and Fourier transform infrared. The dimensions and properties of the isolated nanofibers were followed at the different processing stages using optical microscopy, transmission electron microscopy, atomic force microscopy, and tensile properties (wet and dry). The diameter of the microfibrils was in the range of 7-30 nm for untreated and pretreated bagasse pulps while larger microfibrillar bands (to 150 nm wide) were observed for untreated bagasse pulp than the pretreated pulps (to 90 nm wide). Nanopaper sheets made from nanofibers isolated from alkali- and xylanase-treated pulps showed better wet and dry tensile strength than those made from the other pulps.

This study describes the development of cell-wall damage, i.e., the creation of cracks across or in the vicinity of pits during the testing of twenty microtomed spruce (Picea abies karst.) samples in the Environmental Scanning Electron Microscope (ESEM). Samples were investigated both in an unloaded condition and under a constant tensile load and at different moisture levels. Regions of the moisturecycled samples that had been exposed to an electron beam during image acquisition showed damage running through pits and their surroundings. Specimens loaded in the green condition and dried in the chamber for 2 h without beam exposure except during imaging showed no noticeable cell-wall damage. The results indicate that the electron beam may be a major source of damage initiation. Therefore, it is essential to note the circumstances of the test when explaining the observations made in ESEM studies.

Gypsum fiber composite (GFC) is a kind of building material widely used in interior decoration. Milling is the most commonly used machining process for GFC. Cutting force as an important cutting characteristic parameter has significant influence on the quality of machined surface, power consumption, and tools wear. The tangential force (F_x) and normal force (F_y) were measured and analyzed to find out the effects of milling parameters on these cutting forces. Milling parameters considered were spindle speed, feed rate, and depth of cut. The response surface methodology (RSM) was selected to develop mathematical models and optimize milling parameters. The results showed that with the increase of feed rate and depth of cut, the F_x and F_y increased. But the cutting forces decreased with the increase of spindle speed. The optimization results indicated that high spindle speed, low feed rate, and small depth of cut are preferable for milling of GFC to obtain the best result.

To evaluate the quality of laminated particleboard, a typical type of laminate was used in laminating particleboard with operational parameters similar to industry operation. Pull-off tests using Elcometer 510 were conducted. In addition, panel vertical density profiles (VDP) and the pH of particleboard at different layers were tested. The results showed that the laminated panel bonded by polyvinyl acetate (PVA) glue had higher pull-off strength than that of the phenol formaldehyde (PF) glue within corresponding sanding thickness. Sanding off 0.0762 mm resulted in higher pull-off strength than sanding off 0.0254 mm. The laminates had the highest pull-off strength when the PB were sanded off 0.0762 mm and glued by PVA. This has provided a solution to improve lamination pull-of strength for industry. The test results have also shown that the laminated panels produced in the manufactures have the potential to be improved. It also indicates that Elcometer 510 is a good tool to evaluate the particleboard lamination quality.

In this study, 90 boards of Norway spruce (Picea abies (L.) Karst.) sized 48 x 148 mm in cross-section, have been examined using different scanning and measurement techniques. All of the boards originated from a sawmill located in southern Finland. Planar X-ray scanning, microwave scanning, and grain-angle measurement have been performed. In addition, strength and elastic properties were assessed for eachpiece by four point bending. The purpose of the study was to relate the potential of microwave scanning compared to other, industrially available techniques and to explain the physiological background of the microwave responses. The results show that the microwave signal, after transmission through wood, contains information about the bending strength and the modulus of elasticity. The correlation to densityis a key factor. Annual ring width was also found to be correlated both to microwave measurements and strength properties.

Compression wood is a feature in softwoods that is undesired in sawn wood products due to its tendency to bend and crook as the moisture content changes. An automatic compression-wood detection method was developed and tested on southern yellow pine lumber in the green condition. Sixteen lumber specimens were scanned using both a color camera and an X-ray scanner. Color information was shown to have significant and consistent differences between compression wood and clear wood. However, X-ray information was found to contain large density variations in green lumber due to inconsistent moisture content that would mask density variations arising from compression wood. Therefore, it was concluded that X-ray information would not be useful in detecting compression wood in green southern yellow pine lumber. A multivariate regression model was developed based only on color information from one of the board samples. A nonlinear prediction model was produced by using the original color image data and expanded variables derived from the color images. The model based on one board sample was then applied on all boards. Classified images of the board surfaces were produced and compared to manually detected compression wood. An overall accuracy of 87% was observed in the classification of compression wood.

The aim of the study was to investigate the possibility of predicting the strength of centerboards from Norway spruce (Picea abies (L.) Karst.) saw logs, based on simulated X-ray LogScanner measurements. The study was based on eight logs. The logs were scanned using computed tomography (CT), four centerboards were sawn from each log, and the bending stiffness (MOE) and strength (MOR) of the boards were measured. The CT-images were used for simulations of the industrial X-ray LogScanner, resulting in simulated measurements of knot volume and the green density of heartwood. Finally, multivariate models were calibrated using Partial Least Squares (PLS) regression. These models predict bending strength and stiffness based on the variables measured by the simulated X-ray LogScanner. Both bending strength and modulus of elasticity were defined as the mean value of the four boards from each log. The results were very promising, with strong models for prediction of both MOR (R2 = 0.73) and MOE (R2 = 0.94) mean values for all four boards from each log. The results indicate that the X-ray LogScanner can be used for the sorting of saw logs according to strength and stiffness. The next step should be to repeat the study on a larger sample of material.

When forming fiberboards, a large amount of air is evacuated from the dry fiber mat and the fibers are subjected to forces generated by the flow. If the forces become too strong, the fiber mat bursts and the process stops with financial loss as a result. A simplified model for the pressure field during the pressing has been derived, by starting from first principles. This model indicates that the velocity of the belt can be increased as long as the length of the press is increased, or the viscosity of the penetrating fluid is decreased in a prescribed manner. The model furthermore suggests that the pressure distribution will be unaffected by variations in the basis weight of the fiber mat as long as the basis weight is matched with an equal change in the density of the fibers. Furthermore, by numerically deriving the pressure field as a function of boundary conditions, it is shown that minor variations in the pressure at the nip may result in huge differences in the pressure at the entrance of the press. In a validating procedure, it is shown that model parameters can be adjusted in a physically reasonable way to obtain acceptable agreement with experimental data, but also that the model must be considerably improved in order to obtain quantitative conformity.

Close to the finalization of the medium density fiberboard process, a fairly thick bed of loosely entangled fibers is compressed in a belt-press to often less than a tenth of its original unstressed thickness. This single unit operation is very important to consider when the manufacturing process of the boards is to be optimized. Despite this, there is a lack of knowledge of the interaction between the fiber mat strength and how the fluid flows through it, i.e. de-aeration. Thus, it is of greatest importance to find reliable methods for studying this stage of the manufacturing process. Following this quest, a method is developed with which the gas permeability of fiber mats can be measured. The method offers the potential to measure the permeability at different flow rates and thus at arbitrary pressure gradients through the material. The method is successfully validated with a porous reference material consisting of polymer spheres, and it is shown that the flow follows Darcy's law at the flow rates of interest. Finally, the method is demonstrated by a presentation of permeability measurements on fiber mats consisting of spruce fibers.

This paper studies the relationship between apparent density and some anatomical propertiesof Eucalyptus nitens such as vessel frequency, vessel area, ring width, fiber cell wall thicknesses, andfiber length. The study involved 29 trees from 10 families of Eucalyptus nitens cut from a 17-yr-oldplantation in Southern Chile. The properties were determined along the radial direction of the trees byusing X-ray equipment and at selected positions through microscope and fiber quality analyzer equipment.The results showed that the anatomical properties of E. nitens did not change gradually from pith tobark, but they were better described by dividing the tree radius into three different wood-zones referred as inner-, middle-, and outer-wood. The apparent density of E. nitens was dependent of the vessel area,cell wall area, ring width, and latewood width. The correlation coefficient between apparent density andvessels area was negative and the correlation coefficient between apparent density and cell wall area,latewood ring width, and total ring width were positive. These means that E. nitens wood with lowerdensity tended to have higher vessel area, and lower fiber cell wall area, ring width, and latewood width.

The world’s political and economic decisions are increasingly determined by resource and energy scarcity and by climate change. In these circumstances, a balance must be achieved between economics, ecology and social welfare, which was put forward at the end of the 20th century and has been irrevocably linked to forestry ever since. It is essential that the forest sector is placed at the centre of the developing bio-based economy. The value of the forest for mankind and the environment is irrefutable, and the value of the multitude of products made of wood is of great importance, socially, economically and environmentally. Over the last fifty years, sawn timber in particular has largely disappeared from many technological applications diminishing its contribution to sustainability in the one area where it could be most significant: as a substitute for energy-intensive materials (e.g., in the built environment). However, there is currently a resurgence of interest in timber products due to the environmental benefits they provide, a phenomenon that other industrial sectors are well aware of. This paper discusses the role of thermal wood processing in a sustainability of resource utilization context and what thermal wood processing should achieve to contribute to the European low-carbon economy.

Previous studies have shown that a CT scanner can be used to accurately measure spiral grain in logs. However, the application of such a CT scanning system is of limited use in an industrial application because of the cost and processing time associated with CT scanning. The aim of this study was a preliminary assessment of predicting fiber orientation, an indication of spiral grain, in center-boards from Norway spruce (Picea abies) saw logs using an X-ray log scanner. The scanner is a high-speed commercial log-scanning device used to grade and sort logs based on internal quality characteristics. In this study, nineteen logs were first scanned with a CT scanner. Afterwards, the CT images were used to simulate X-ray log scanner images, with which measurements of different variables such as diameter, taper, percentage of heartwood, density, and density variations could be calculated. Depending on the log diameter, two to four centerboards were then sawn from each log, and the fiber orientations of the boards were measured for observed spiral grain for each log. A statistical model for predicting fiber orientation was then developed using partial least squares (PLS) regression. The PLS-model was developed to predict the fiber orientation of a log at a distance of 50 mm from the pith based on different variables that are measurable with the industrial X-ray log scanner. The resulting PLS-model was shown to produce an R2 = 0.45 for the training set and R2 = 0.55 for the test set. The statistically significant variables used to predict spiral grain were green heartwood density, knot volume, and a measure of the unsymmetrical distribution of knot volume. Significant correlation of these variables warrants further research and development with the X-ray log scanner to nondestructively sort out logs with excessive spiral grain.

There is demand in the Swedish sawmill industry to improve the accuracy of moisture content measurements, both to obtain a better tool to run production and to ensure that the products meet customer expectations. In this study, 240 well-conditioned pieces of Scots pine (Pinus sylvestris), sorted into five different groups by visual inspection, were measured using microwaves and X-rays. Models to predict moisture content of wood were made by measurements of an additional 45 pieces of wood. Using only measured quantities from the microwave system, ie attenuation and phase shift, the root mean square error (RMSE) of the estimated moisture content was 1.00%. By adding total density from the X-ray measurements, RMSE of the estimated moisture content was lowered to 0.89%. Mean errors of the different wood groups varied from -0.65 to 0.18%.

This is the second part of a two-part study aimed at examining the effect of extreme adhesive pH on bond durability. The first part dealt with short-term exposure and this second part dealt with long-term exposure. This part also included an examination of wood degradation by adhesive pH.Nine structural wood adhesives [four high pH phenol formaldehyde (PF), one intermediate pH phenol-resorcinol formaldehyde (PRF), two low pH melamine formaldehyde (MF), and two low pH melamine-urea formaldehyde (MUF)] were studied in terms of their pH effect on wood-adhesive bond durability using Douglas-fir wood substrate with specimens tested in block shear. The block shear specimens were initially subjected to vacuum-pressure treatment under water, followed by exposure, while wet, at 50°C for 0, 4, 8, 12, and 17 months. At each exposure period, the specimens were dried to their original moisture content prior to testing for shear strength and evaluation of wood failure.Indications of the extent of degradation of the wood layer adjacent to the bond line due to adhesive pH during the long-term exposure were also examined by the 1% sodium hydroxide solubility test. There were indications that the wood layer closest to the bond line, which contained included glue, had higher solubility compared to those farther from the bond line. This suggests that wood degradation and/or adhesive decomposition occurred and was considered to be induced by the adhesive alkalinity or acidity under the long-term exposure conditions.The PF showed the best durability performance followed, in decreasing order, by PRF and MF/MUF. The latter adhesives degraded completely after an exposure period of 8 to 17 months.The four PF adhesives passed the shear strength and wood failure requirements of the well-known North American structural wood adhesive standards indicating that their high pH had no significant detrimental effect on the wood-adhesive bond durability after the 17-month exposure period despite their being subjected to multiple cyclic tests. This observation was not apparent for the PRF, and the pH effect was considered inconclusive for the MF/MUF since they degraded during the exposure period.The results of this study provide support to wood adhesive standards that do not impose restriction on the upper spectrum of the pH range, and would be useful to adhesive standard developers. These results also serve as background information for adhesive companies in their formulation of wood adhesives as well as for bonded wood product manufacturers in their use of adhesives and for builders in their use of bonded wood products.

The ability of wood to buffer and mitigate the effects of strongly acidic or alkaline environ- ments produced near the glue line by extreme pH structural adhesives was evaluated. The pH values of wood, cured adhesives, and mixtures of the two in water slurries were determined for different wood types. The pHs of slurries of seven highly alkaline phenol–formaldehyde adhesives were lowered when the adhesive was cured in the presence of wood dust with effects increasing with the proportion of wood in the mixture. The “acidities” or amounts of alkali needed to adjust the slurries to pH 12.5 were relatively high for all species because of weak acid groups in wood that dissociate at pH greater than 8. This explains the ability of wood to buffer highly alkaline adhesives. The pHs of slurries of two acidic melamine–urea–formaldehyde adhesives increased in the presence of wood, but the effect was less significant compared with the alkaline adhesives. Similarly, the “alkalinities” or amounts of acid required to adjust the slurries to pH 3 were relatively low. Aspen veneer samples had a greater effect on adhesive pH than spruce and Douglas-fir. These effects will help mitigate potentially adverse effects of strongly alkaline or acidic adhesives on wood adhesive bond strength.

This study is one part of a whole project called "Impact of Extreme pH of Structural Adhesives on Bond Durability." The objective of this study was to evaluate effects of pH on wood-adhesive bond strength and chemical change in aspen (Populus tremuloides Michx) wood caused by extreme pH exposures. Aspen veneer lap-shear samples were tested for maximum stress (N/mm2) and wood failure (%) after exposure to soaking in different buffered solutions (pH = 2.0, 2.5, 3.0; water, 10.0, 11.0, 11.5, 12.0, and 12.5) for 1, 4, and 7 mo. One set of samples stored in laboratory conditions was also tested as a control at each test time. Results indicated that bond strength and wood failure decreased after 4- and 7-mo exposures to acidic conditions but did not change significantly under alkaline exposures. However, the buffered acidic solutions (pH = 2.0 and 3.0) did not cause a measurable chemical change in aspen wood, whereas losses in hemicellulose and lignin were found after aspen wood specimens had been exposed to pH > 11.0 buffered solutions.