Wood and Fiber Science (E-Journal)
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Technical Note: Analysis of Mechanical Relaxation Intensity of Wood at Various Moisture Contents
Get PDFThis study analyzed mechanical relaxation data by the well-known Gaussian function from which the relaxation intensity was determined for various moisture contents over a range of temperatures (-81-0°C). These data were used to suggest a range of bonding mechanisms for sorbed water
Rapid Assessment of Southern Pine Decayed by G. Trabeum by Near Infrared Spectra Collected from the Radial Surface
Get PDFThe use of near infrared (NIR) spectroscopy for predicting levels of degradation in southern pine (Pinus spp.) by Gloeophyllum trabeum for periods over 1-8 da was investigated. NIR spectra collected from the center of the radial face of each sample after laboratory soil block decay tests were used to develop calibrations. Calibrations were developed for mass loss, compression strength, and exposure period using data measured from prior methods and untreated and mathematically treated (multiplicative scatter correction and first and second derivative) NIR spectra from various ranges of wavelengths by partial least squares regression. Strong relationships were derived from the calibrations with the strongest R2 values of 0.97 (exposure period), 0.94 (compression strength), and 0.91 (mass loss). Calibrations for exposure period showed the strongest statistics for predicting wood decay of the validation test set (R2 = 0.92; RPDp [ratio of the standard deviation of the measured data to the standard error of prediction] = 3.95 [first derivative, 1100-2250 nm]), while predictions for mass loss of the decayed samples resulted in R2 = 0.86 and an RPDp = 3.17 (multiplicative scatter correction, 1100-2500 nm), and the strongest compression strength prediction resulted in R2 = 0.76 and an RPDp = 2.50 (second derivative, 1100-2500 nm). These results suggest that NIR spectroscopy can adequately predict wood decay from spectra collected from the radial face of southern pine
Technical Note: The Susceptibility of Chemically Treated Southern Hardwoods to Subterranean Termite Attack
Get PDFOngoing research into chemically treating southern hardwoods for producing structural composite lumber suggests that some improvements may be imparted by modifying the wood. How chemical treatment(s) affect modified wood durability, particularly resistance to Reticulitermes flavipes, was the objective of this study. Water-saturated samples of yellow-poplar, sweetgum, and red oak were heated at 150°C for 30 min in two solutions: water and 1.0% NaOH; controls were also included. Samples were subjected to the AWPA E1-09 no-choice termite test in which mass loss from R. flavipes was determined. The species and treatments independently and significantly affected the mass loss. Yellow-poplar, which had the lowest specific gravity, averaged significantly greater mass loss than sweetgum and red oak for all three exposures. All species treated in water or NaOH showed a higher degree of termite degradation as compared with the controls
Effects of Esters and Resorcinol on Phenolic Resins as Adhesives in Medium-Density Fiberboard Manufacturing
Get PDFPhenol-formaldehyde (PF) resin-bonded composite wood panels exhibit very low formaldehyde emission levels, meeting the most stringent regulations. However, slow cure speed is a major limiting factor for its applications in the economical manufacturing of medium-density fiberboard (MDF) and particleboard. Commercial PF resins accelerated with esters or resorcinol and their applications in the manufacturing of MDF were investigated in this article. It was found that although ethylene carbonate, propylene carbonate, and triacetin were very effective in reducing the gel time of phenolic resins, these esters caused substantial loss of bonding strength, particularly in the case of phenolic resins with high alkalinity. The loss of bonding strength increased as the ester loading level in the PF resin was increased. On the other hand, resorcinol was not only an effective PF accelerator, but also preserved most of the bonding strength. Resorcinol-accelerated PF adhesives showed better performance in internal bond strength, bending strength, and water resistance of MDF in comparison with the ester-accelerated PF adhesive systems. The cure speed of the resorcinol-accelerated PF adhesive was evaluated against a urea-formaldehyde (E2 type) in the manufacturing of MDF
Development of a Method to Predict the Bending Strength of Lumber Without Regard to Species Using X-Ray Images
Get PDFSeveral models have been developed for predicting bending strength of lumber using X-rays, but most require species-specific classifications. However, the classification is very difficult because logs or cants can arrive without leaves or bark. This study was carried out to develop an alternative bending strength prediction model that does not lose precision when the species is unknown. The study proposes an Equivalent Density Model (EDM), in which a cross-section is quantified as equivalent density. Because the relationship between density and strength of small clear specimens is not affected by species, the EDM was expected to correlate to strength regardless of species. This model predicted the modulus of rupture in two species with R2 = 0.73, although the two were mixed. Therefore, it may be possible to predict bending strength using X-rays without classifying lumber by species
Magnetic Resonance Microimaging of Liquid Water Distribution in Sugar Maple Wood Below Fiber Saturation Point
Get PDFMagnetic resonance (MR) microimaging was used to determine the distribution of liquid water in sugar maple wood (Acer saccharum Marsh.). Two moisture desorption tests were applied using saturated salt solutions at 21°C. Desorptions were accomplished between 58 and 96% RH starting from the full saturation state and from the FSP. Each moisture sorption condition at equilibrium was associated with a MR microimaging scan. Signal intensity (represented by false colors in the MR images) allowed visualization of the concentration of liquid water distributed into the wood structure. In most cases, the presence of liquid water was noticed in samples coming from the full saturation state at moisture contents below FSP. This result shows the coexistence of liquid and bound water even at moisture contents below the FSP. The remaining liquid water in the wood appears to be located principally in the lumina of the least accessible libriform fibers
Tensile and Impact Properties of Steam-Exploded Wood-Polypropylene Composites
Get PDFWood-plastic composites were made from polypropylene and steam-exploded (SE) flour from small-diameter loblolly pine. SE wood content, maleic anhydride grafted polypropylene (MAPP) content, and extruder screw speed were investigated using an orthogonal test design to examine their effects on tensile and impact properties of the composites. The results showed that as SE wood-flour content was increased, the modulus of elasticity (MOE) of the composites also increased, whereas the tensile strength decreased. The MAPP content had a distinct effect on the tensile strength and no such effect on MOE; however, it had no clear trend for the impact properties of the composites. The wood content had distinct effects on both the tensile and impact properties of the composites. The screw speed also affected the tensile and impact properties of the composites
Use of Adjacent Knot Data in Predicting Bending Strength of Dimension Lumber by X-Ray
Get PDFIn a previous study, the knot depth ratio (KDR) evaluation method was proposed to quantify the area of knots in a cross-section. That study reported that bending strength can be predicted by KDR analysis. However, the KDR model did not take into consideration the additional strength reduction caused by adjacent knots. It was found that the prediction of lumber strength was improved when adjacent knots were taken into consideration. Analysis using the KDRA (KDR adding knots) model revealed that the optimum cross-sectional interval, an input variable, is directly affected by knot size parallel to lumber length (KSPLL). KSPLL depends on the sawing method and log characteristics, and for species containing large knots, the cross-sectional interval is likely to be extremely wide. This can cause several adjacent small knots to be excluded from the analysis, requiring modification of the KDRA model algorithm. This modification resulted in improvement in the precision of the strength prediction, although the input variable of the cross-sectional interval was not used. The R2 values obtained using this method were 0.60 and 0.56 for Japanese larch and red pine, respectively
Real-Time Measurement of the Viscoelasticity of Green Juvenile Wood of Japanese Cedar at High Temperature
Get PDFChanges in the viscoelasticity of green juvenile and mature wood during high-temperature drying were measured in real time. For each measurement, a 180-mm-long specimen of Japanese cedar (Cryptomeria japonica), its supporting system, a magnetic driver, and a deflection sensor were placed in an electric oven and a free-free flexural vibration test was performed. The temperature was fixed at 120°C. The resonance frequency decreased and the loss tangent increased during heating of the juvenile vs mature wood. These tendencies apparently occurred because the initial moisture content of the juvenile wood was higher than mature wood and because the juvenile wood had the larger number of intercellular layers
Innovation Activities in the Primary Wood Products Sector: A Case Study
Get PDFThe goal of this article is to understand how wood products industries located in Virginia incorporate innovation into their business processes through a case study methodology. Based on innovation theory and previous studies in innovation, a case study that included interviews, on-site visits, and analysis of documents was designed and applied to four industries in the wood primary sector to 1) identify innovation activities into four categories: product, process, marketing, and organizational management; and 2) to understand, describe, and explain the source of innovation in these firms and to develop an innovation research model for further research. All four firms performed innovation activities mostly at the product development level and the source of innovation is primarily from external sources. Using the results, a conceptual model to further study innovation in the primary wood products sector was defined. This model will be tested using a different methodology in subsequent research. The application of the case study was very useful to understand the source of innovation and how primary wood products firms perform innovative activities at various levels