This study investigates the effect of the relative proportion of copper oxide (CuO) to didecyl dimethyl ammonium carbonate (DDACb) in an alkaline copper quat (ACQ) formulation on the rate of copper fixation or stabilization and the resistance of treated wood to leaching of copper and quat (DDACb) for different ACQ retentions in wood. Red pine, jack pine, and black spruce samples were treated with ACQ at concentrations of 0.6, 1, and 1.5 percent with CuO to DDACb ratios of 2:1 (the usual ratio for ACQ-D), 1:1, and 1:2. Red pine samples posttreated at 50°C were evaluated for rate of fixation by the expressate method. Conditioned samples of the three species were evaluated for the leaching of copper, and DDACb (red pine). At similar ACQ retentions, a decrease in proportion of copper in the formulation resulted in a substantial reduction in the time required for copper fixation. There was a significant decrease in the amount of copper leached for all three species studied with reduction of proportion of copper in the ACQ formulation. Improved fixation time and reduced copper leaching resulted from the lower copper retentions in the samples with lower relative proportions of copper in the formulations. The reduction in leaching was higher for samples treated with concentrations of 1 and 1.5 percent ACQ. The formulation having a 1:1 CuO to DDACb ratio appears to be the most promising, considering the positive effects of reduced copper ratio on copper leaching and fixation time and the minimal effect on DDAC leaching.
The new copper-based preservative systems leach a relatively high level of copper and, thus, generate some environmental concerns. Polyvinyl alcohol (PVOH) is known to complex with copper(II) and is water soluble. The effect of co-addition of fully hydrolyzed PVOH on the leaching of copper from wood treated with three different copper salts was examined. Southern pine sapwood wafers were treated with copper sulfate, copper acetate, and ammoniacal copper carbonate, all with 1 percent elemental copper in the waterborne solution, with and without 2 percent PVOH. The wafers were then dried and water leached for 2 weeks. PVOH co-addition greatly reduced the copper leached from wood treated with alkaline ammoniacal copper carbonate but not from wood treated with a slightly acidic solution of copper acetate or highly acidic copper sulfate.
Disposal of decommissioned chromated copper arsenate (CCA)–treated wood as landfill has become an important environmental concern. Reusing and recycling decommissioned treated wood seems to be the most practical environmental solution to the problem. In a previous report, 6-ply laminated beams made from decommissioned CCA-treated southern pine (Pinus spp.) wood utility poles and 6-ply laminated beams made from untreated virgin wood were studied to evaluate the effects of surface preparation method and cross-sectional region (high or low CCA retention) on bonding shear strength, wood failure, and delamination. In this study, 6-ply laminated beams having the same composition as those of the previous study were made and then pressure-treated (i.e., retreated) with CCA prior to being evaluated in the same manner as in the previous study. This study revealed that gains in CCA retention (as a result of retreatment with CCA) for beams made from decommissioned utility pole wood were similar to the gains for beams made from untreated virgin wood. CCA retreatment had little overall effect on either glue-line shear strength or wood failure of beams made from decommissioned wood utility poles, but overall substantially increased shear strength and wood failure of beams made from virgin wood. CCA retreatment also reduced the delamination of both beams made from decommissioned utility pole wood and beams made from virgin wood. Additional testing is warranted to further investigate the bonding performance of decommissioned CCA-treated transmission utility pole wood.
A study was conducted to evaluate various substitutions of cotton burr and linters from cotton gin waste (CGW) as natural fiber reinforcements in ligno-cellulosic polymer composites (LCPC). Samples were fabricated with approximately 50 percent natural fiber, 40 percent high-density polyethylene, 4 percent mineral filler, and 6 percent lubricant, by weight. The experiment included substituting wood fiber in LCPC with 25, 50, 75, and 100 percent (by weight) cotton burr (CB) and cotton burr mixed with 2 percent (by weight) second-cut linters (CBL), respectively, with the remaining fraction as wood fiber and comparing it against the control (100% wood). Samples were extruded into rectangular profiles and tested for physical and mechanical properties such as specific gravity (SG), water absorption, thickness swelling, coefficients of linear thermal expansion (CLTE), flexural strength and modulus, compressive strength, hardness, and nail withdrawal force (NWF). The CB and CBL treatments exhibited SG, CLTE, hardness, and NWF comparable to the control. However, the water absorption and thickness swelling, flexural strength and modulus, and compressive strength all deteriorated at high substitution rates of CB and CBL. The favorable properties of cotton burr included its tendency to decrease CLTE and increase hardness of LCPC.
The effect of varying proportions of maleic anhydride polypropylene (MAPP) on the physical and mechanical properties of polymeric diphenylmethane diisocyanate (pMDI)–bonded oriented strand board panels was investigated. Additionally, two forms of MAPP (powder and emulsion) were used to determine the effect of MAPP type on panel properties. Panels were produced by combining southern yellow pine (Pinus spp.) flakes with 4 percent pMDI binder and 0, 1.5, 3, 4.5, or 6 percent powdered or emulsified MAPP. Addition of emulsified MAPP decreased panel mechanical properties regardless of addition level. Powdered MAPP had a negligible effect on panel modulus of elasticity and only produced significant decreases in panel modulus of rupture and internal bond strength at the highest addition level (6%). Emulsified MAPP effected greater reductions in panel mechanical properties relative to powdered MAPP. Increasing levels of emulsified MAPP caused undesirable increases in both 24-hour water absorption and thickness swelling. Powdered MAPP did not provide a significant improvement over control panels in water absorption and thickness swell tests. Addition of either powdered or emulsified MAPP appeared to have a negligible effect on panel permeance.
This study presents the evaluation of some important properties of sandwich-type panels made from bamboo (Dendrocalamus asper) and rice straw (Oryza sativa). A total of 32 experimental panels with an average target density ranging from 0.65 to 0.80 g/cm3 were produced. The sandwich-type experimental panels were made from a mix of 95 percent bamboo and 5 percent rice straw particles as the core layers and a mix of 95 percent bamboo and 5 percent rice straw fibers as the face layers. Mechanical properties of the specimens, including modulus of elasticity, modulus of rupture, internal bond strength, hardness, face screw holding strength, formaldehyde emission, thickness swelling, and surface roughness, were determined. Experimental results showed that both physical and mechanical properties of the samples were favorable. Panel type D, with 50 percent fiber and 50 percent particle and a density of 0.80 g/cm3, had the highest strength characteristics. Mechanical properties of the panel satisfied the minimum requirements for interior particleboard panels for general use based on Japanese Industrial Standard A-5908 of 1995. It appears that using only 5 percent rice straw did not adversely influence overall properties of the samples. This study indicates that bamboo and rice straw furnish can be used as a viable alternative to wood in the form of three-layer, sandwich-type panels with enhanced surface quality as substrate for thin overlays to manufacture panels products for furniture and cabinet units.
Thermal conductivity values for ash, oak, silver wattle, poplar, and beech were measured. Thermal conductivity coefficients of the wood species were determined for radial and tangential directions at four different moisture conditions, ranging from 0 to 22 percent moisture content (MC). Equations predicting thermal conductivities of the wood species according to the MC are proposed in the tangential and radial directions. The thermal conductivity test was performed with a quick thermal conductivity meter based on the ASTM C1113-99 hot-wire method, and measurements were carried out at a room temperature of 20°C to 24°C. The effect of density and porosity on thermal conductivity was also investigated. Results showed the behavior of all wood species studied is quantitatively similar. Thermal conductivity increased with increasing MC. Tangential thermal conductivity values within the MC range of 0 to 22 percent changed from 0.089 to 0.147 W/m-K for poplar, 0.127 to 0.222 W/m-K for beech, 0.113 to 0.202 W/m-K for ash, 0.142 to 0.290 W/m-K for silver wattle, and 0.130 to 0.219 W/m-K for oak. Tangential thermal conductivity was similar to radial thermal conductivity. Radial thermal conductivity was 1.08 times tangential thermal conductivity for poplar, 1.01 times for beech, 1.06 times for ash, 0.95 times for silver wattle, and 1.03 times for oak, respectively. The data are useful when calculating the energy required to kiln-dry lumber and predicting the thermal insulating qualities of log homes made from the species.
Because of the large percentage of juvenile wood in small-diameter southern pine, this material has lower strength properties compared with the historic published values in the ASTM Standard D2555. Finding new, simple, and inexpensive ways of increasing these strength properties would increase the use of this material for residential construction. For this study, we chose in situ polymerization using the monomer 1,6-hexanediol dimethacrylate to enhance bending strength and stiffness. After determining the lower range of density, modulus of rupture (MOR), and modulus of elasticity (MOE) of juvenile wood from small southern pine logs, southern pine specimens were polymerized using both a vacuum-impregnation and a surface-application approach. The results showed some significant physical property increases for the fully impregnated material that used a large amount of monomer. Although the surface-application approach used less monomer, the physical properties of the juvenile wood did not increase as expected. Only the 1-minute dip treatment showed a significant increase in both bending stiffness and strength, with a weight gain of 11.9 percent. For the surface-application approach, monomer moving to the wood surface during polymerization reduced their effectiveness in increasing MOR and MOE to the expected levels. Therefore, the challenge is finding a method that maintains polymer loading inside the wood structure during the curing process.
The mechanical properties of Abies pinsapo Boiss., a relict species from the south of Spain, have been studied very little due to its scarcity and the high level of protection of this species. Forest fire prevention measures involving felling of mature trees have enabled the species to be characterized for the first time. A comparison of its three regions of provenance, (1) Sierra de Grazalema, (2) Sierra Bermeja, (3) Sierra de las Nieves, was included in this evaluation. Tests were conducted using small dimension defect-free test pieces in accordance with the corresponding Spanish mechanical property test standard. In order to relate the findings to the wood anatomy, measurements were taken of tracheid length and diameter, tracheid wall thickness, and growth rate. The mean values per region of provenance (1, 2, 3) were Charpy impact strength, 16.9, 12.4, 14.3 (J); modulus of rupture (MOR), 74.9, 68.8, 71.1 (N/mm2); tensile strength perpendicular to the grain (tangential), 1.9, 2.0, 1.8 (N/mm2); tensile strength perpendicular to the grain (radial), 2.0, 2.0, 1.9 (N/mm2); splitting strength, 2.4, 2.3, 2.3 (N/mm); and compressive strength parallel to the grain, 40.0, 39.9, 39.9 (N/mm2). The findings showed that the values of most of the properties studied in the three regions of provenance did not present statistically significant differences.
Statistical reliability methods are applied to estimate the upper percentiles of strand thickness for the face layers of oriented strand board (OSB) panels manufactured from six mills in the Eastern United States. The influence of thick strands on OSB properties (thickness swell, TS; internal bond, IB; and modulus of rupture, MOR) has been well documented. However, there is an absence in the literature of characterizing wood strand thickness for OSB mills in the context of statistical reliability methods. With induced percentile left censoring for improved model fitting, bootstrapping methods are employed for better estimating the upper percentiles and confidence intervals for strand thickness. The upper percentiles of flakes may be costly, damage equipment, or cause dimensional instability in OSB. The distributions of wood strands were nonnormal, and best-fit distributions varied from the log-logistic, largest extreme value, lognormal, and Weibull. The mean and median strand thicknesses for all mills were 0.0322 inches (0.8179 mm) and 0.0310 inches (0.7874 mm), respectively. The coefficient of variation for all mills was 39.1 percent. Parametric bootstrap confidence intervals for the 95th percentile with no censoring varied in length from 0.0009 inches (0.0229 mm) to 0.0145 inches (0.3683 mm). Nonparametric bootstrap confidence intervals for the 95th percentile with no censoring varied in length from 0.0005 inches (0.0127 mm) to 0.0225 inches (0.5175 mm). Study results were strengthened from the validation study in that the training intervals were either contained within, or overlapped, the validation intervals.
The in-line moisture meter at the planer measures the moisture content of every board. This information is often not used for process improvement because of difficulty in linking the moisture information to a point in the process and reliable statistical methods for analyzing the data. Test programs in which the moisture contents measured at the planer were used to create process charts for kilns and to identify kilns or zones within kilns with high moisture content or moisture content variability were established in four mills. Tagging units, either with bar codes or with alphanumeric tags, to identify their location in a kiln was a practical and effective way to diagnose kiln performance when the moisture content information collected at the planer was associated with location. Wet areas and dry areas could be identified, and the consistency of moisture content from charge to charge could be evaluated, as could the variability within charges. The latter items can be accomplished without knowing the location of a unit in the kiln if the kiln from which the lumber came is known at the time of planing. The methods developed also allow other factors, such as operator decisions and the performance of in-kiln moisture meters, to be evaluated.
Primary wood processing and secondary furniture production are strategic sectors in most western Balkan countries with regard to contribution to gross domestic product, exports, and employment. After abandoning a socialist business system in the post-Yugoslavia era, all countries in the region have developed transitional reforms to become free-market economies. Some of these reforms include changes in ownership structure, recapitalization and modernization, adapting to meet import standards of developed countries, and developing strategic linkages with supply-chain counterparts in developed countries. This article contains the results of research conducted on the current situation in primary wood processing and furniture industries in seven western Balkan countries. A common characteristic of these sectors across all countries is the century-long tradition of forestry and forest utilization. The development of these sectors will require sustainable management of the region's rich forest resources, political and economic systems that are transparent and market driven, as well as investments in production technology and employee training.