Modeling longleaf pine (Pinus palustris Mill) wood properties using near infrared spectroscopy

This research demonstrated model development for important wood properties using near infrared spectroscopy (NIR); it considered the effect of outside sources of error, and the ability of NIR to measure fiber morphology. Strength, stiffness, and density were successfully modeled from wood samples taken throughout 10 longleaf (Pinus palustris Mill) trees. Principal components and multiple linear regression were compared for performance in prediction of density, strength, and stiffness. I found both modeling techniques to yield similar prediction accuracies. However, I found that density could be estimated through Beer-Lambert’s law since the absorbance at all wavelengths increased with density. Also, 5 of 6 wavelengths needed to predict strength were also needed to predict stiffness lending support that similar chemical morphology controls the covariance between strength and stiffness. Klason lignin, extractives, and microfiber angle (MFA) were also measured throughout the tree. I found extractives, lignin, and MFA to decrease from the pith outward regardless of height. A theoretical model was built attempting to explain how lignin content and MFA co-vary. Theoretical and empirical spectroscopic models both predicted MFA with nearly similar root mean square error and supported that lignin was a probable factor responsible for the covariance in spectra with MFA. Tracheid length was another secondary trait investigated. I demonstrated that tracheid length could be predicted with an R2 of 0.71 due to NIR spectra response with age. Accurate tracheid length prediction was possible due to systematic variation of chemistry with age except for at ring 1 and 4 where some other unknown factor was responsible. Finally, blue stain and machine variability were investigated as two sources of extraneous error. It was of interest to know if the common extraneous error would bias a prediction equation. With proper modeling, I found I could avoid the blue stain variation present in the spectra when modeling modulus of elasticity (MOE), modulus of rupture (MOR), density, lignin, and extractives. However, when a calibration was built from one machine and then applied to a population of scans made from a separate machine, blue stain became problematic and prediction of MOE, MOR, and extractives were biased

Effect Of Processing Parameters, Resin, and wax Loading On Water Vapor Sorption of Wood Strands

The outdoor use of oriented strandboard (OSB) is undesirable if exposed to atmospheric vapor or rain; however, increasing resin and wax content can mitigate adverse sorption behavior of panels under such negative conditions. The objective of this study was to investigate the effect of resin loading, emulsion wax loading, and pressing parameters on the water vapor sorption behavior of loblolly pine strands. Pure earlywood of loblolly pine (Pinus taeda) strands were cut and oven-dried at 50°C. The phenol-formaldehyde resin or wax was sprayed on the wood strands, which were oven-dried at 50°C for 900 s. All specimens were equilibrated at 11% relative humidity (RH) over a saturated salt solution. After equilibration, specimens were placed in a conditioning chamber with the RH increasing from 11-80%. The mass change was continuously recorded by a dynamic contact angle analyzer. The results show that platen temperature, wax loading, compression ratio, and resin loading were influential, in decreasing order, on sorption behavior

Effect of Microcrystalline Cellulose, Species, and Particle Size on Mechanical and Physical Properties of Particleboard

Particleboards made from both sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) were made at a small and large particle size and at 0 and 10% microcrystalline cellulose loading. Modulus of rupture, modulus of elasticity, work to maximum force, and thickness swell (after 2 and 24 h) were measured for all treatment combinations. An increase in particle size had a positive influence on mechanical properties but also allowed for more thickness swell, particularly for the southern pine furnish. Conversely, adding cellulose actually decreased mechanical properties, increased thickness swell, and decreased springback. In the field, the ability to manipulate particle size to control particleboard mechanical properties is perhaps more cost-effective and practical than cellulose addition. Replacing southern pine with sweetgum was viable with equal or better mechanical and physical properties. This suggests that the hardwood species could be a feasible substitute for pine as the demand for woody resources in the southern US continues to grow

Reliability Testing of AlGaN/GaN HEMTs Under Multiple Stressors

We performed an experiment on AlGaN/GaN HEMTs with high voltage and high power as stressors. We found that devices tested under high power generally degraded more than those tested under high voltage. In particular, the high-voltage-tested devices did not degrade significantly as suggested by some papers in the literature. The same papers in the literature also suggest that high voltages cause cracks and pits. However, the high-voltage-tested devices in this study do not exhibit cracks or pits in TEM images, while the high-power-tested devices exhibit pits

Formosan and Native Subterranean Termite Attack of Pressure-Treated SPF Wood Species Exposed in Louisiana

This study evaluated the relative ability of three types of wood preservatives to inhibit attack by Formosan subterranean termites (FST) (Coptotermes formosanus Shiraki) and native subterranean termites (Reticulitermes spp.). The study also evaluated the roles of preservative retention and penetration in preventing termite damage. Sections of boards from six wood species within the Spruce-Pine-Fir species group were pressure-treated with one of four concentrations of a borax-copper (BC) preservative composed of 93% borax (sodium tetraborate decahydrate) and 7% technical copper hydroxide or one concentration of disodium octaborate tetrahydrate (DOT) or chromated copper arsenate (CCA). Specimens were cut after treatment, exposing untreated end-grain in specimens not completely penetrated by preservative. The specimens were exposed above-ground, protected from the weather, at a site with populations of both native and FST near Lake Charles, Louisiana. Specimens were rated for extent of termite attack after 6, 12, and 24 months of exposure. Attack by FST was more severe than that by native termites for all preservative treatments, although this difference was less obvious at higher preservative retentions. For all treatments, termites preferred to attack the center of the end-grain of the specimens where preservative was either absent or at a lower concentration. However, CCA, which had the lowest overall penetration, was more effective than either borate preservative in preventing attack, whereas some DOT- and BC-treated specimens suffered attack even with what appeared to be complete boron penetration. These results indicate that the efficacy of shell treatments in preventing termite attack is a function of the type of preservative. The BC wood preservative protected wood from both native and Formosan termite attack at B2O3 concentrations equivalent to or lower than that of DOT treatments

Ability of Near Infrared Spectroscopy to Monitor Air-Dry Density Distribution and Variation of Wood

Process control of wood density with near infrared spectroscopy (NIR) would be useful for pulp mills that need to maximize pulp yield without compromising paper strength properties. If models developed from the absorbance at wavelengths in the NIR region could provide density histograms, fiber supply personnel could monitor chip density variation as the chips enter the mill. The objectives of this research were to a) develop density histograms from actual density versus density histograms developed through NIR modeling, and b) determine the precision of density models developed from absorbance in the NIR region with a recommendation for the sample size needed to estimate the standard deviation of density at a given precision.Models for density were developed from calibration samples (n = 170) and then validated with 93 randomly held aside samples. The samples were systematically removed from 10 longleaf pine trees of equal age, but different growth rates. The histogram patterns for actual density almost paralleled the histogram patterns developed from predictive models. Subsequently, the validation data set was randomly categorized into groups of three, and the standard deviations of density were measured. For three measurements per data point, the predicted standard deviation covaried with the actual standard deviation of density with an R2 = 0.61 and 0.55 for the calibration and validation data set, respectively. A sample size of 30 was recommended to estimate the standard deviation of density with a precision of 0.01 g/cm3

Technical Note: Melt Dispersion Technique for Preparing Paraffin Wax Microspheres for Cellulose Encapsulation

A practical and convenient approach for making paraffin wax microspheres with a melt dispersion technique was reported in this study. Surfactants were melted in water by water bath and then added to a flask after the wax was completely melted with stirring. Paraffin wax microspheres were generated by cooling. The obtained microspheres exhibited uniform diameters in the range of 10-60 μm observed with a scanning electrical microscope and were mainly dependent on the surfactant ratio. Encapsulated microcrystalline cellulose particles with the previously mentioned conditions were also generated and demonstrated the possibility of encapsulating microcrystalline cellulose with some acceptable agglomeration, although some encapsulated individually. Encapsulation of cellulose could be beneficial if agglomeration could be minimized and the encapsulated microcapsules could be dispersed during blending for wood composites manufacture

Oriented strand board with improved dimensional stability by extraction of hemicelluloses

Oriented strand board (OSB) panels are commonly used for wooden building structures such as Walls, floors, ceilings, and furniture. These wood composites are manufactured with small wooden strands held together in specific orientations by adhesives. Other additives such as wax might be added to reduce water absorption. One of the limitations of the panels produced today is their poor performance under high humidity conditions. The goal of the present work was 1) to extract hemicelluloses from pine wood strands before the fabrication of OSB panels and 2) to test the impact of the pretreatment on the dimensional stability of these panels. For that purpose, pressure-assisted hydrothermal processes at three different temperatures (120, 140, and 160oC) were performed for 45 min of extraction time in each case. Hemicelluloses in treated wood strands were quantified using high-performance liquid chromatography. Water absorption, thickness swell, MOE, MOR, and internal bond strength were measured to assess the influence of the pretreatment on OBS properties. According to the results, a hydrothermal pretreatment is beneficial for the performance of OSB panels at high humidity levels. The pretreatment of pine strands at 160oC allowed for the maximum removal of hemicelluloses, without a significant degradation of cellulose or lignin, and the OSB panels pretreated with these pinewood strands displayed the best performance in dimensional stability under wet conditions.

The Response of Visible/Near Infrared Absorbance to Wood-Staining Fungi

The influence of blue-stain fungi [Ophiostoma minus (Hedgcock) H. and P. Sydow and Leptographium serpens (Goid.) Siemaszko] on absorbance at the visible and near infrared wavelengths was investigated. Forty trees were sampled at breast height from longleaf pine (Pinus palustris Mill.). One half of each increment core was inoculated with one of two fungi treatments while the other half served as a control. Visible and near infrared spectra were acquired between rings 3-40 for the stained and control-clear wood samples (n = 304). Absorbance was greater for the stained than the control wood at wavelengths between 464 to 1334 nm. Statistical techniques were applied to the NIR data to determine which wavelengths, and their corresponding chemical assignments, were most affected by the fungi. First and 2nd derivative pretreatments to the original spectra resulted in some blue-stain sensitive wavelengths throughout the 350 to 2500 nm range, some of which are associated with nitrogen in the melanin present in blue stain. However, for the 2nd derivative pretreatment, the stained wood exhibited a different signal to noise ratio than the control wood, and thus the pretreatment method should be used with vigilance. For the raw, 1st, and 2nd derivatives, the absorbance of L. serpens (n = 164) significantly differed from O. minus (n = 140) between 424-554 nm. The results of this study are important because the absorbance at visible and NIR wavelengths may be used to classify stained wood