Treesearch

Deterioration is broadly defined as any negative effect on the properties of a material. The effects can be due to biological attack or to various non-living agents (sunlight, moisture, temperature), but often, deterioration results from a combination of factors. Nowhere is this more evident than with WPCs, owing to the marriage of dissimilar materials. This article examines agents that can damage WPCs, explores methods for limiting this damage, and then addresses long-term methods for assessing WPC properties related to durability.

Water-resistant bonds are important in many wood products and have been hard to obtain with many bio-based adhesives. Using a three-step process, water-soluble soy flour has been converted into adhesives that cure into an insoluble material for water-durable adhesives. The process consists of denaturation of soy flour, followed by modification with formaldehyde and then conversion via co-polymerization with a suitable cross-linking agent into an insoluble material. Both formaldehyde and phenol-formaldehyde are used across-linking agents. The extent of conversion into the cross-linked...

Red pine (Pinus resinosa Ait.) butt logs from 38 year old research plots were used to study the effect of plantation stand density on kraft pulp production. Results indicate that plantation stand density can affect pulp yield, unrefined pulp mean fibre length, and the response of pulp fibre length to pulp refining. However, the effect of plantation stand density on physical and optical properties of paper was not significant and within the measurement errors of data obtained from testing handsheets. Therefore, we conclude that pulp and paper properties should not be a factor affecting...

The mechanical properties of paper at a single basis weight and a single targeted refining freeness level have traditionally been used to compare papers. Understanding the economics of corrugated fiberboard requires a more global characterization of the variation of mechanical properties and refining energy consumption with freeness. The cost of refining energy to increase paper performance is of the same magnitude as the cost of adding fiber to obtain an equal increase in performance; the costs of energy and fiber vary dramatically with geography and market conditions. We provide formulas...

The research presented elucidates the oxidation chemistry occurring in hydrogen peroxide bleached kraft pulp fibers by employing carbon near edge x-ray absorption fine structure spectroscopy (C-NEXAFS). C-NEXAFS is a soft x-ray technique that selectively interrogates atomic moieties using photoelectrons (Xrays) of variable energies. The X1A beam line at the National Synchrotron Light Source (NSLS) was employed to probe carboxylic acid groups that display a signature absorption band at 289 eV. This study is the capstone to a larger effort to support the mechanistic basis for lignocellulosic...

Efforts to comply with effluent standards have led to a situation where mills have little leeway in managing trace metals without developing mineral scale deposits. In most cases, the trace metals can be managed with minor process changes and siitable levels of process control. The principal tools available to the mill are pH and good washing in the first chorine dioxide stage washer. In some cases, mills may need to change shower sources on washers or upgrade the Do washer. By determining the chmical equilibrium for critical points in the process and in some cases modeling the chemical...

The current wood construction codes find their origin in the 1935 Wood Handbook: Wood as an Engineering Material published by the USDA Forest Service. Many of the current design recommendations can be traced back to statements from this book. Since this time a series of development both historical and recent has led to a multi-layered system for use of wood products in the United States. The following paper will first discuss the wood construction design criterion referenced by model codes used in the United States; second, touch on product standards; third, briefly discuss US model codes...

When treated wood is used in field settings, the possibility of environmental contamination raises concerns. There is increasing pressure to be environmentally friendly and to reduce, restrict, or eliminate the use of wood preservatives because of the concern that toxic constituents may leach from the treated wood. This report will provide an overview of preservative systems, help readers understand the level of risk and status of the science involved in evaluating preservative systems, and provide some guidelines for using the products.

Treated wood has generally been more difficult to bond than untreated wood for a variety of reasons. Alkaline copper quat (ACQ) and copper azole (CA-B), the most prominent substitutes for chromated copper arsenate (CCA), are difficult to bond consistently. Using a phenol-resorcinol- formaldehyde (PRF) adhesive formulated for bonding to CCA-treated wood, we examined the bonding of southern yellow pine treated with CCA, ACQ, or CA-B. In durability tests, bonds were not as durable in the ACQ-or CA-B-treated southern yellow pine as in the CCA-treated or untreated pine as measured by delaminatio...

The North American lumber market is integrated and, under normal conditions, provides unhindered access to all suppliers. North American log markets, in contrast, function on different principles: in one principle, a profit allowance for the wood processor plays a role in timber pricing, whereas in the other it is a byproduct of the give-and-take of arm’s length market negotiations. Under the first system, markets are characterized by high elasticities of price transmission and, at times of market weakness, by low elasticities of product supply. Under the second system, the opposite of...