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A fundamental understanding of mat consolidation during hot pressing will help to optimize the medium-density fiberboard (MDF) manufacturing process by increasing productivity, improving product quality, and enhancing durability. Effects of panel density, fiber moisture content (MC), and pressing schedule on formation of vertical density profile (VDP) during hot pressing were investigated. Different pressing schedules in which the platens were quickly closed to positions of 160%, 140%, 120%, 100%, and 90% of final target thickness then more slowly brought to final target thickness were...

Pichia stipitis is widely studied for its capacity to ferment d-xylose to ethanol. Strain improvement has been facilitated by recent completion of the P. stipitis genome. P. stipitis uses CUG to code for serine rather than leucine, as is the case for the universal genetic code thereby limiting the availability of heterologous drug resistance markers for transformation. Development of a modified selectable marker for resistance to bleomycin (Sh ble) and efficient excision of the marker after integration (loxP/Cre) should facilitate functional genomics and metabolic engineering in this...

Down-regulation of the gene encoding 4-coumarate 3-hydroxylase (C3H) in angiosperms massively but predictably increased the proportion of p-hydroxyphenyl (P) units relative to the normally dominant syringyl (S) and guaiacyl (G) units. Alfalfa stem levels of up to ~65% P (from wild-type (WT) levels of ~1%) resulting from down-regulation of C3H were measured by traditional degradative analyses as well as 2D 13C– 1H correlative NMR methods. Such levels put these transgenics well beyond the P:G:S compositional bounds of normal plants. NMR also revealed structural differences in the interunit...

The increased use of alkaline copper quaternary (ACQ) and copper azole (CuAz) as wood preservatives for residential construction has led to concerns about the corrosion performance of fasteners. Information on the effects of these preservatives on the corrosion rate is limited, although Simpson Strong Tie has published a technical bulletin indicating that both ACQ and CuAz are roughly twice as corrosive as chromated copper arsenate (CCA) and recommends fastener types for a given environment and preservative (Simpson Strong Tie 2005). It is believed that ACQ and CuAz are more corrosive than...

Leaching of wood preservatives affects the long-term efficacy and environmental impact of treated wood. Soil properties and wood characteristicscan affectleaching of woad preservatives, but these effects are not well understood. This paper reports a statistical analysis of the effects of soil and wood properties on leaching of arsenic (As) and copper (Cu) from southern yellow pine sapwood treated with chromated copper arsenate (CCA-C). Specimens were leached by an accelerated laboratory method for 12 weeks in soil obtained from different locations or in water. Loss of Cu and As was...

Much of the literature on the bonding of wood and other lignocellulosic materials has concentrated on traditional adhesion theories. This has led to misconceptions because wood is a porous material on both the macroscopic and microscopic levels. A better understanding of wood bonding can be developed by investigating the theories of adhesion and bond strength, taking into consideration the unusual structure of wood. Wood is not uniform in the millimeter, micrometer, and nanometer scales. The interaction of adhesive with wood needs to be considered on these different spatial scales. In...

Design properties of wood are currently established at the macroscale, assuming wood to be a homogeneous orthotropic material. The resulting variability from the use of such a simplified assumption has been handled by designing with lower percentile values and applying a number of factors to account for the wide statistical variation in properties. With managed commercial forests geared toward rapid growth and shorter rotation harvests, wood products now contain significantly fewer and more widely spaced growth rings, further stretching the validity of the assumption of homogeneous...

This paper presents a model using finite element method to study the response of a typical commercial corrugated fiberboard due to an induced moisture function at one side of the fiberboard. The model predicts how the moisture diffusion will permeate through the fiberboard’s layers(medium and liners) providing information on moisture content at any given point throughout the structure. The hygroexpansion response and the creep response were predicted through the development of a finite element model capable of capturing the behavior of the fiberboard. Comparing the results generated from...

The state of the art among most industry citations of box compression estimation is the equation by McKee developed in 1963. Because of limitations in computing tools at the time the McKee equation was developed, the equation is a simplification, with many constraints, of a more general relationship. By applying the results of sophisticated finite element modeling, in this current study we derive a more general box compression formula that preserves the underlying theory of the McKee equation but removes the constraints. This formula is solvable with modern spreadsheet software, and we...

Since 1991, thermal load histories for various roof cladding types have been monitored in outdoor attic structures that simulate classic North American light-framed construction. In this paper, the 2005 thermal loads for wood-based composite roof sheathing, wood rafters, and attics under wood-plastic composite shingles are compared to common North American roof cladding materials, solid wood shingles and black-and white-fiberglass shingles. WTPC-shingles have appeared to suffer no damage after over three-years of weathering and solar exposure. The summertime thermal load data for flakeboard...