Treesearch

Wood, like many natural materials, is hygroscopic; it takes on moisture from the surrounding environment. Moisture exchange between wood and air depends on the relative humidity and temperature of the air and the current amount of water in the wood. This moisture relationship has an important influence on wood properties and performance. Many of the challenges of using wood as an engineering material arise from changes in moisture content or an abundance of moisture within the wood. This chapter discusses the macroscopic physical properties of wood with emphasis given to their relationship...

This article highlights major aspects of a new optical technique to determine the surface area of a threaded fastener; the theoretical framework has been reported elsewhere. Specifically, this article describes general surface area expressions used in the analysis, details of image acquisition system, and major image processing steps contained within the measurement system. In short, the general approach is to acquire a high contrast image, break the complicated fastener geometry into smaller defined segments with known analytical solutions, calculate the surface area of each individual...

A January 2004 change in the regulation of wood preservatives used in the U.S.has increased the use of newer wood preservatives, such as alkaline copper quaternary (ACQ) and copper azole (CuAz). These preservatives contain high amounts of cupric ions, which may be reduced to copper metal at the expense of less noble steel and galvanized fasteners in the wood. Preliminary testing using extreme accelerating conditions suggested newer preservatives are more corrosive than the previously used chromated copper arsenate (CCA), although it is unclear how corrosion rates measured in these extreme...

Our forests are a naturally renewable resource that has been used as a principal source of bio-energy and building materials for centuries. The growth of world population and affluence has resulted in substantial increases in demand and in consumption for all raw materials. Resulting increases in demand for wood products provides a unique opportunity for developing new generations of renewal, sustainable and materials efficient bio-based composites. The 100-year history of the softwood plywood industry provides a good example of a successful development of an idea, a process, and eventually...

Composites made from thermoplastics and fillers or reinforcements derived from wood or other natural fibers are a dynamic research area encompassing a wide variety of composite materials. For example, as the use of biopolymers grows, wood and other natural fiber sources are being investigated as renewable sources of fillers and reinforcements to modify performance. Nanocellulose, whether cellulose nanocrystals or fibrillated cellulose, have interesting characteristics and offer new composite opportunities if efficient, economical, and scalable methods of producing both the reinforcements...

Wood-plastic composite (WPC) lumber has been marketed as a low-maintenance, high-durability product. Retail sales in the United States were slightly less than $1 billion in 2008. Applications include docking, railing, windows, doors, fencing, siding, moldings, landscape timbers, car interior parts, and furniture. The majority of these products are used outdoors and thus are exposed to moisture, decay, mold, and weathering. WPCs are composites made primarily from wood or cellulose-based materials and plastic(s). The wood utilized is usually in particulate form, such as wood flour or very...

In the quest to manufacture and use building materials that are more environmentally friendly, soy adhesives can be an important component. Trees fix and store carbon dioxide in the atmosphere. After the trees are harvested, machinery converts the wood into strands, which are then bonded together with adhesives to form strandboard, used in constructing long-lasting houses. Soybeans fix both carbon dioxide and nitrogen and can be converted into flour that can be made into a waterborne adhesive for bonding wood strands together. Although soy and other protein adhesives were used for centuries...

Over the past several years, at least three pulp mills in North America have experienced catastrophic events that resulted in the explosion of pumps, mixers, and tanks. All these mills were using 50% concentration hydrogen peroxide at the site of the explosions. In at least two instances, alkali catalyzed decomposition of peroxide is implicated in the explosion. Although many mechanical pulping facilities use hydrogen peroxide to bleach pulp, no alkali-catalyzed explosions have been reported. The current work uses a kinetic model of peroxide decomposition to explain why the peroxide...

Southern pine specimens vacuum-treated with nano-zinc oxide (nano-ZnO) dispersions were evaluated for leach resistance and UV protection. Virtually, no leaching occurred in any of the nano-ZnO–treated specimens in a laboratory leach test, even at the highest retention of 13 kg/m3. However, specimens treated with high concentrations of nano-ZnO showed 58–65% chemical depletion after 12 months of outdoor exposure. Protection from UV damage after 12 months exposure is visibly obvious on both exposed and unexposed surfaces compared to untreated controls. Graying was markedly diminished,...

Hot-pressing wood, particularly in the production of wood composites, generates significant ‘‘native’’ (wood-based) formaldehyde (FA), even in the absence of adhesive. The level of native FA relates directly to the time and temperature of hot-pressing. This native FA dissipates in a relatively short time and is not part of the long-term FA emission issue commonly associated with hydrolyzing urea-formaldehyde bonds. This paper demonstrates that the common desiccator/ chromotropic acid method is very specific for FA and is not influenced by other volatile compounds set free from wood during...