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...

Variability, or variation in properties, is common to all materials. Because wood is a natural material and the tree is subject to many constantly changing influences (such as moisture, soil conditions, and growing space), wood properties vary considerably, even in clear material. This chapter provides information, where possible, on the nature and magnitude of variability in properties. This chapter also includes a discussion of the effect of growth features, such as knots and slope of grain, on clear wood properties. The effects of manufacturing and service environments on mechanical...

The mission of the USDA Forest Service is to sustain the health, diversity, and productivity of the Nation’s forests and grasslands to meet the needs of present and future generations. All Forest Service activities, conducted through the National Forest System, Forest Service Research and Development, and State and Private Forestry, are intended to help sustain forests and grasslands now and into the future. The Forest Service manages over 193 million acres (78 million hectares) of National Forests and Grasslands for sustainable multiple uses to meet the diverse needs of people, ensure the...

All wood is composed of cellulose, lignin, hemicelluloses, and minor amounts (usually less than 10%) of extraneous materials contained in a cellular structure. Variations in the characteristics and proportions of these components and differences in cellular structure are what give the wood its unique physical properties, such as heavy or light, stiff or flexible, hard or soft. The properties of a single species are relatively constant within limits; therefore, selection of wood by species alone may sometimes be adequate. However, to use wood to best advantage and most effectively in...

Properties of cellulose nanocrystals (CNCs) depend upon their supramolecular structures, which are important to understand in order to optimize their applications. In this investigation, the structures of CNCs produced upon 48–64% H2SO4 hydrolysis of hydrothermally-treated poplar, bleached kraft pulp cotton microcrystalline cellulose, bacterial cellulose, tunicin, and cladophora cellulose were comparatively analyzed. TEM provided information on the morphological aspects. Raman, MAS-NMR, and XRD provided information on one aspect of the supramolecular organization, namely, crystallinity...

Brown rot fungi utilize iron as part of a chelator-mediated Fenton (CMF) reaction during wood biodegradation. Research suggests these fungi reduce Fe3+ to promote oxygen radical generation resulting in depolymerization of the wood cell wall. High levels of Mn are also found in wood decayed by brown rot fungi. However, little is known about the oxidation states of Fe and Mn during the decay process. X-ray absorption near edge spectroscopy (XANES) can be used to examine metal oxidation states and coordination chemistry. XANES experiments were conducted on wood decayed by Gloeophyllum trabeum...

In October, the aggregate U.S. housing market was mixed. Assessing the month-over-month data yielded decreases for multifamily permits and under construction, all three completion categories, and new single-family sales. Year-over-year, most categories were positive, with the exceptions of multifamily starts and permits, and single-family completions. Residential construction spending was positive month-over-month and year-over-year; and expenditures in August, September, and October are the greatest since the residential surge of 2005–2006. Housing remains a bright spot for the U.S. economy.

In November, the aggregate (month-over-month and year-over-year) U.S. housing market indicators were positive. November housing data denoted the second consecutive month of total starts greater than 1.5-million units. The single-family subsector is the primary source of the current uptrend and is progressively gaining momentum. Month-over-month data yielded decreases in four categories: total and multifamily completions, new single-family and existing sales. Similarly, year-over-year data indicated declines for multifamily starts and permits, and total and single-family completions....

December housing data denoted the second consecutive month of total starts greater than 1.5 million units. For the fourth consecutive month, total starts exceeded their 61-year historical average. Further, single-family starts were the greatest since September 2006 (1,384,000 units). Aggregate (month-over-month and year-over-year) U.S. housing market data also were positive. The single-family subsector is the primary source of the current uptrend and is progressively gaining momentum. Month-over-month data yielded decreases in three categories: aggregate multifamily starts and permits, and...

The first research on acetylation of wood started in 1928, and the first research done on acetylation of wood at the USDA Forest Service Forest Products Laboratory (FPL) started in 1945. This is a review of the research done between 1945 and 1966 at the FPL. This research was the first to show that acetylated wood was both decay-resistant and dimensionally stable. It was the pioneering research that ultimately led to the commercial production of acetylated wood.