Deterioration of wood-based boards subjected to outdoor exposure in Tsukuba
Various types of wood-based boards were analyzed for deterioration after being exposed to an outdoor environment for 5 years in Tsukuba, Japan. In phenol–formaldehyde resin bonded particleboard (PB(PF)) and aspen oriented strand board (OSB(aspen)), longer exposure caused a greater reduction in the modulus of rupture and internal bond strength, an increase in the coefficients of variation, and a decrease in 95 % lower tolerance limit at the 75 % confidence level (95TL). Nail-head pull-through and lateral nail resistance were also reduced by outdoor exposure, but their coefficients of variation and 95TL were not significantly affected. In contrast, methylene diphenyl diisocyanate bonded medium density fiberboard (MDF(MDI)) only showed a slight deterioration of these properties even after 5-year exposure, and the coefficients of variation and 95TL hardly changed. After 5-year exposure, the retention of shear load in one-plane at relative displacement of 1.0 mm was high in MDF(MDI) and OSB(aspen) at 93.5 and 78.5 %, respectively, but low in PB(PF) at 41.1 %. As with PB(PF), OSB(aspen) also showed a sharp decrease in the modulus of rupture and internal bond strength, but only slightly reduced shear load in one-plane.
Effect of flakeboard manufacturing variables on composite properties: Part 1, Effect of resin content, wax content, pressing conditions, and edge treatments on paint performance
Over the last several decades, oriented strandboard (OSB) and similar composite materials (flakeboard) have been successfully used to sheath residential, and to some extent, commercial structures. However, when used as exterior siding, they have often failed, often even if they were painted. The performance of OSB and flakeboard has not been consistent when used outdoors. Little is known of how manufacturing parameters, such as the amount of adhesive (resin), water repellent (wax and similar products), pressing conditions, and other factors, such as geographic area and paint, affect performance. We report the effect of these parameters on painted flakeboard exposed at the Forest Products Laboratory outdoor exposure sites near Madison, Wisconsin, and Gulfport, Mississippi. The study also evaluated the effect of a bevel and edge sealing on the drip edge . We found that a single coat of paint failed within a year because of dimensional change and debonding of flakes, particularly the areas of the boards having large flakes. Statistically significant effects were noted for exposure location, resin content, and edge sealing. The amount of wax had a positive effect only for flakeboard having low resin content. Those boards having 3.5% isocyanate resin performed better than those having 2.0% isocyanate res n and edge sealing generally decreased thickness-swell. INTRODUCTION Background Over the last several decades, oriented strandboard (OSB) panels have performed quite well as sheathing for residential structures when protected from the weather; however, when used as exterior siding (i.e., cladding), OSB panels often performed poorly, particularly if not overlaid with resin-impregnated paper. When used as siding, either as a panel product or cut into strips to give lap siding, edges of these products tended to delaminate, absorb moisture, and swell. Paint often failed by cracking and flaking. These failures relate to poor understanding of various OSB components (such as type of wood, resin, and wax), processing variables, drip-edge configuration, and finishes used on these products (edge seals and paint). Performance of painted OSB relies on an interaction between two completely different materials and the industries manufacturing these materials-the wood industry (OSB) and paint industry (edge sealers and finishes). These industries rarely cooperate in joint research to understand the complex nature of the interactions of these different materials as they age during outdoor exposure, nor does industry take into account the different climates where their products are used. Researchers in the Performance-Engineered Composites and Performance Enhanced Biopolymers Research Work Units at the Forest Products Laboratory (FPL) investigated this complex combination of materials. Several previous studies reported interactions of finishes with flakeboard or OSB, but manufacturers in the United States no longer make these finishes. Hann et al. (1962) made flakeboard from Douglas-fir (Pseudotsuga menziesii) furnish using several blends of phenolicand urea-based resins. They evaluated the effects of temperature and moisture under static and cyclic conditions in laboratory tests and compared the laboratory results with specimens exposed outdoors for 3 years. Some of the specimens exposed outdoors were painted. The face was painted with one coat of exterior under-coat and one top-coat of white-gloss house paint and the edges with several coats of paint. Some specimens were not painted. Details on the type of paint were not reported, but they were probably oil-alkyd paints, as water-borne latex paints were seldom used in exterior applications in 1962. Unpainted panels degraded markedly; however,
The Study of Relationship between Berm Width and Debris Flow at the Slope
The purpose of this study is to estimate the behavior and the mechanism of debris flow at the end of mountain side when a berm was set on the inclined plane. The numerical model was performed by using the Finite Difference Method(FDM) based on the equation for the mass conservation and momentum conservation. In order to measure the behavior of the debris flow, the debris flow of a straight channel slope and the debris flow of channel slope with 3 types of berms were compared. First, the flow discharge and the sediment volume concentration at the downstream of the channel slope, depending on the various berm width and the different inflow discharges at the upstream of the channel were analyzed. The longer the berm width, the flow discharge at the downstream of the channel was decreased and the high flow fluctuation was reduced by a berm. And it means that a berm can effect for the delay of the debris flow. Through Root Mean Square ratio(RMS) comparison, the flow discharge of the channel slope with a berm was lower than that of a straight channel slope. The longer the berm width, for the sediment volume concentration, an inflection point did not show but mild curve. Because the low sediment concentration with water mixture by a berm continuously flow at the downstream end, it will be effect for reducing the disaster caused by debris flow. The results of this study will provide useful information in predicting and preventing disaster caused by the debris flow.