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Biocides must be developed for controlling mould establishment on cellulose-based building materials. Accordingly, biocides intended for indoor applications must be non- toxic, non-volatile, odourless, hypoallergenic, and able to provide long-term protection under conditions of high humidity. Multi-component biocide systems were tested in American Wood-Preservers’ Associations oil block tests for inhibition of brown-rot and white-rot decay fungi and American Society for Testing and Materials standard tests for inhibition of mould fungi and termites. Multi-component systems combining a...

Composites of wood in a thermoplastic matrix (wood–plastic composites) are considered a low maintenance solution to using wood in outdoor applications. Knowledge of moisture uptake and transport properties would be useful in estimating moisture-related effects such as fungal attack and loss of mechanical strength. Our objectives were to determine how material parameters and their interactions affect the moisture uptake and transport properties of injection-molded composites of wood-flour and polypropylene and to compare two different methods of measuring moisture uptake and transport. A...

The mechanical properties of newly developed aspen fiber–polypropylene composites (APC) were experimentally explored and numerically predicted at the temperatures and humidity that are typical for domestic housing applications. The mechanical properties of APCs with five different fiber-loadings were evaluated at the room temperature, 4 [degrees] C, and 40 [degrees] C. Environmental effects on the mechanical properties of APCS were experimentally quantified after conditioning the APCs with two different fiber-loadings in the following temperature and humidity for over 7000 h: (1) hot/dry...

In traditional mechanics of materials, the stiffness of a beam or plate in bending is described by its cross-sectional shape as well as its material properties, primarily the modulus of elasticity. Previous work at the USDA Forest Products Laboratory, Madison, Wisconsin, has shown that modulus of elasticity has a strong correlation to the density of the fiberboard. Examined here are experimental and theoretical relationships between process variables of bulk density and area density and the transverse bending stiffness of the fiberboard. A model is developed and evaluated for the relationsh...

When dry wood is placed in water, the water not only fills the lumen (void in the cells) but also diffuses into the cell walls, causing them to expand. Although the wood becomes weaker via this cell wall plasticization, failure generally increases in the bondline rather than in the wood under wet conditions. Thus, the question is why water exposure often causes a greater decrease in bondline strength than in wood strength. In a few cases, such as un- crosslinked poly(vinyl acetate), bondline failure comes from the adhesive’s decreased structural integrity because of plasticization under...

Moisture management remains the most critical factor for controlling mold growth on wood and wood products during storage, construction, and while in service. When moisture management practices fail to adequately control moisture, plant extracts demonstrating antifungal properties may provide protection for these applications. The objective of this study was to evaluate the antifungal properties of natural plant extracts, such as essential oils, for use on wood. Seven essential oils were evaluated for their ability to inhibit growth of Aspergillus niger, Trichoderma viride, and Penicillium...

Small specimens of sheathing-grade oriented strandboard (OSB) and sheathing-grade plywood were evaluated for retention of mechanical properties in exterior exposure over a series of exposure times. In contrast to previous studies of this nature, specimens at prolonged exposure times were also evaluated (in something more than a cursory manner) for presence of decay. Specimen size and mounting configuration had been selected to maximize wetting and drying induced stress on adhesive bonds but discourage water retention and thus the likelihood of decay. Mechanical properties decreased...

Diethyl oxalate (DEO) was injected into a digester containing wood chips (pine, spruce, or aspen) preheated to 130–1408C and held for 30 min at the same temperature. When mechanical pulps were produced from these pretreated chips, savings in electrical refiner energy could be achieved. For southern yellow pine (Pinus taeda), the electrical refiner energy required to produce pulps with Canadian standard freeness (CSF) of 100 ml was 38– 55% less than for an untreated control. Energy savings were also observed for aspen (Populus spp.) and spruce (Picea spp.). DEO-treated pine handsheets...

Wood chips of pine, spruce, aspen, and maple were treated at 135–1408C with diethyl oxalate (DEO) and analyzed for extractable and residual carbohydrates. Under these conditions, DEO hydrolyzes to ethanol and oxalic acid (OA). The amount and identity of carbohydrates released from the chips were species-dependent. For all wood species, increasing the amount of chemical, time, or temperature resulted in an increment in carbohydrates released. Approximately 50% (by wt) of extracted carbohydrates were monosaccharides. In addition, acetic acid was detected in the water extracts. When extracts...

During weathering, wood-plastic composites (WPCs) can fade and lose stiffness and strength. Weathering variables that induce these changes include exposure to UV light and water. Each variable degrades WPCs independently, but can also act synergistically. Recent efforts have highlighted the need to understand how WPCs weather, and to develop schemes for protection. The first plan of attack is often to adapt photostabilizers currently used to protect polyolefins in WPCs. Another effective option is to improve the surface of the WPCs by changing manufacturing methods and/or conditions. This...