Wood and Fiber Science (E-Journal)
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SORPTION AND SURFACE ENERGY PROPERTIES OF THERMALLY MODIFIED SPRUCE WOOD COMPONENTS
Full text linkThe objective of this work is to study the water vapor sorption and surface energy properties of thermally modified wood (TMW) components, ie wood processing residuals in the form of sawdust. The thermal modification was performed on spruce wood components using a steam-pressurized laboratoryscale reactor at two different temperature (T) and relative humidity (RH) conditions, T . 150°C and RH . 100% (TMW150), and T . 180°C and RH . 46% (TMW180). A dynamic vapor sorption (DVS) technique was used to determine water vapor sorption isotherms of the samples for three adsorption-desorption cycles at varying RH between 0% and 95%. Inverse gas chromatography (IGC) was used to study the surface energy properties of the samples, including dispersive and polar characteristics. The DVS results showed that the EMC was reduced by 30-50% for the TMW samples compared with control samples of unmodified wood (UW) components. A lower reduction was, however, observed for the second and third adsorption cycles compared with that of the first cycle. Ratios between EMC of TMW and that of UW samples were lower for the TMW180 compared with the TMW150 samples, and an overall decrease in such EMC ratios was observed at higher RH for both TMW samples. The IGC results showed that the dispersive contribution to the surface energy was higher at lower surface coverages, ie representing the higher energy sites, for the TMW compared with theUWsamples. In addition, an analysis of the acid-base properties indicated a higher KB than KA number, ie a higher basic than acidic contribution to the surface energy, for all the samples. A higher KB number was also observed for theTMWcompared with theUWsamples, suggested to relate to the presence of ether bonds from increased lignin and/or extractives content at the surface. The KB was lower for TMW180 compared with TMW150, as a result of higher modification temperature of the first, leading to cleavage of these ether bonds.
SEISMIC DESIGN OF CROSS-LAMINATED TIMBER BUILDINGS
Full text linkThe increasing interest in cross-laminated timber (CLT) construction has resulted in multiple international research projects and publications covering the manufacturing and performance of CLT. Multiple regions and countries have adopted provisions for CLT into their engineering design standards and building regulations. Designing and building CLT structures, also in earthquake-prone regions is no longer a domain for early adopters, but is becoming a part of regular timber engineering practice. The increasing interest in CLT construction has resulted in multiple regions and countries adopting provisions for CLT into their engineering design standards. However, given the economic and legal differences between each region, some fundamental issues are treated differently, particularly with respect to seismic design. This article reflects the state-of-the-art on seismic design of CLT buildings including both, the global perspective and regional differences comparing the seismic design practice in Europe, Canada, the United States, New Zealand, Japan, China, and Chile
EFFECT OF PANEL AREA-VOLUME RATIO ON TVOC RELEASED FROM DECORATIVE PARTICLEBOARDS
Full text linkHome renovation can improve our living environment, but it can cause pollution and endanger human health. Wood-based panels are a main source of polluting volatile organic compounds (VOCs). This article studied the VOC concentration of different types of decorative particleboards (PBs) and different panel area–volume ratio, and the effect of panel area–volume ratio on release of various substances. In this study, the main experimental conditions are as follows: the temperature was controlled at 230.5°C; the humidity was controlled at 50%3%; and the rate of ventilation was controlled at once 1 h. And a 15-L small–environmental chamber was used to test the VOC emission. The experimental material was PB with different decorative materials (water-based paint, melamine-impregnated paper, polyvinyl chloride, and PB with no decorative material), and VOC emission was collected under different panel area–volume ratios (1, 1.5, 2, and 2.5m2/m3). The result showed that the VOCs were present, with the trend of decreasing with time. The decline velocity of water-based paint (WP) was the fastest, whereas that of the PB with no decorative material was the slowest. Increase of panel area–volume ratio could cause the VOC concentration to increase, but the panel area–volume ratio does not have a linear relationship with VOC concentration. Surface decoration can reduce the release of various kinds of material inside the plate to a certain extent. Melamine impregnated paper (MI) and polyvinyl chloride (PVC) can reduce the release of aromatic hydrocarbons in panels, and PVC can inhibit the release of esters in panels.
AN ANALYSIS OF HEATING UNIFORMITY IN WOOD HIGH-FREQUENCY DRYING
Full text linkThe high-frequency heating temperature field simulation model was built using finite element method and validated by experiments. Under the premise of ensuring model accuracy, the model parameters (plate spacing and area, wood dielectric constant, stack length and width, and heating time) were individually varied to assess the impact of these parameters on wood heating uniformity. The results showed the following: 1) The model has good accuracy as verified by experiments. 2) In the thickness direction, the middle layer temperature was higher than the upper and lower surface temperatures; in the length and width directions, the center temperature was lower than those of both ends and both sides, and the temperature at the corners was the highest. 3) The smaller the distance between the plates, the better the heating uniformity; with the plate area increasing, the heating uniformity first increased and then decreased; the smaller the wood dielectric constant, the better the heating uniformity; as the continuous heating time increased, the heating uniformity first decreased, then increased, and then again decreased; as the length and width of the stack increased, the heating uniformity decreased first, then increased, and then again decreased; when they were the same size as the plate, the heating uniformity was the best.
Limitations of a 3-D Image Analysis-Based Particle Size Measuring System for Wood Particle Dimension Measurement
Full text linkAgainst the background of inaccurately measured wood particle dimensions, applying the three-dimensional (3-D) image analysis–based particle size characterization system Partimac 3D XL in pre- liminary tests, metal platelets with various aspect ratios of the three main axes are employed to understand and explain the observed limitations of the measuring principle. It was found that particle width and thickness interact increasingly with a decreasing aspect ratio and, thus, the digital replica and subsequent determination of the dimensions become incorrect. This was ascribed to the random orientation of the particles during image acquisition, which cannot be overcome with a finite number of cameras in the system.
GENE EXPRESSION ANALYSIS OF WOOD DECAY FUNGUS FIBROPORIA RADICULOSA GROWN IN ACQ-TREATED WOOD
Full text linkCopper-tolerant brown-rot fungi are able to degrade wood treated with copper or copper-based wood preservatives. This research used quantitative reverse transcriptase polymerase chain reaction to explore what genes of the brown-rot fungus, Fibroporia radiculosa, were expressed when the fungus was overcoming the wood preservatives and decaying the wood. Aryl alcohol oxidase, catalase, oxalate decarboxylase 2, and copper resistance P-type ATPase pump had higher expression on alkaline copper quat type D treated wood compared with week 1. In addition, two genes had high expression at week 5; glycoside hydrolase 5 and glycoside hydrolase 10 when wood strength loss was around 50%. Glyoxylate dehydrogenase had high expression until week 8. This gene might be involved in the production of oxalate. Laccase, oxalate decarboxylase 1 and isocitrate lyase were not differentially expressed, suggesting that these genes were not involved in the decay process of alkaline copper quat-treated wood. These results are important to understand the genes that are involved in the mechanism of copper tolerance and wood decay in F. radiculosa.
TIMBER HARVESTING PATTERNS FOR MAJOR STATES IN THE CENTRAL, NORTHERN, AND MID-ATLANTIC HARDWOOD REGIONS
Full text linkTimber harvesting is a major disturbance agent influencing the composition and structure of eastern hardwood forests. To better understand timber harvesting practices, we examined roundwood harvesting patterns in 13 eastern states in the Central, Mid-Atlantic, and Northern regions that contained high proportional volumes of hardwood in their forest inventories. Nearly 5400 Forest Inventory and Analysis sample plots in which timber was cut and assumed to be used were examined for the period 2009-2015. Nine patterns based on basal area removed were isolated and defined, of which six were partial removals and three were clear-cuts. Of the patterns observed, four involved primarily hardwoods, three involved primarily softwood, and two were mixed. Large diameter–influenced partial hardwood harvesting practices were found to be predominant in the Central hardwood region, but mixed diameter hardwood and softwood partial harvesting patterns were noted in Wisconsin, Michigan and Maine. Harvesting patterns examined in Pennsylvania and New York appeared to be a transition between the patterns found in the Central and three most Northern states. Large diameter–influenced harvesting also occurred less frequently in the Mid- Atlantic states. Clear-cuts were noted in all states examined but were associated with higher levels of removal in the Mid-Atlantic states. Softwood cuts were more common in the Northern and Mid-Atlantic states and pine thinning cuts were noted in Tennessee, Wisconsin, Michigan, Virginia, and North Carolina. Although this study provides insight into current timber harvesting processes, additional information is needed to determine how timber management practices can be developed to complement the economic considerations associated with harvests
