modified wood. Determining adhesive bond performance for chemically modified wood is important not only in relation to its commercial utility but also because this information helps in understanding wood bond durability. Although wood...
moremodified wood. Determining adhesive bond performance for chemically modified wood is important not only in relation to its commercial utility but also because this information helps in understanding wood bond durability. Although wood modification is usually used to improve anti-swell efficiency, the modification can alter adhesive bond performance. Generally, modification is expected to diminish adhesion by making the wood surface less polar and less porous, resulting in poorer adhesive wetting of the wood and fewer chemical bonds between the two surfaces. On the other hand, chemical modification can help the wood bonds to pass water exposure durability tests because modified wood will swell less. Given the great variety of wood adhesives, species, and modification methods, a simple theory does not explain bonding behaviour. However, our model that takes into account the mechanism for dissipating stress induced by moisture-driven dimensional change, as well as general adhesion theo...
Decay resistance of wood-plastic composites reinforced with extracted or delignified wood flour
This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. Properties of Cellulose Degraded by
While it is known that modifying the hydroxyls in wood can improve the decay resistance; what is often missing in the literature is whether these modifications alter wood nanostructure, and how these changes correlate to the improved...
moreWhile it is known that modifying the hydroxyls in wood can improve the decay resistance; what is often missing in the literature is whether these modifications alter wood nanostructure, and how these changes correlate to the improved decay resistance. Here, we used small angle neutron scattering (SANS) to probe the effects of alkylene oxide modifications on wood nanostructure. Southern pine wood samples were chemically modified to various weight percentage gains (WPG) using four different alkylene oxides: propylene oxide (PO), butylene oxide (BO), epichlorohydrin (EpH), and epoxybutene (EpB). After modification, the samples were water leached for 2 weeks to remove any unreacted reagents or homopolymers and then equilibrium moisture content (EMC) was determined at 90% relative humidity (RH) and 27°C. Laboratory soil block decay evaluations against the brown rot fungus Gloeophyllum trabeum were performed to determine weight loss and biological efficacy of the modifications. To assist ...
Reductions in hygroscopicity, increased dimensional stability and decay resistance of heat treated wood depends on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted...
moreReductions in hygroscopicity, increased dimensional stability and decay resistance of heat treated wood depends on decomposition of a large portion of the hemicelluloses in the wood cell wall. In theory, these hemicelluloses are converted to water and volatile furan-type intermediates that can polymerize in the cell wall. Reductions in hygroscopicity and improved dimensional stability of acetylated wood depends on esterification of the accessible hemicelluloses in the cell wall reducing hydrogen bonding with water and bulking the cell wall back to its green volume. Stability is not 100 % since the water molecule is smaller than the acetyl group so water can access hydroxyl sites even when the wood is fully acetylated. The cell wall moisture content is too low in acetylated wood to support fungal attack so the initial enzymatic attack starting the colonization does not take place. The critical sugar in the hemicelluloses that may be the trigger for fungal attack is arabinose as it is...
Determining adhesive bond performance for chemically modified wood is important not only for its commercial utility but also for understanding wood bond durability. Bulking modifications occupy space inside the cell wall, limiting the...
moreDetermining adhesive bond performance for chemically modified wood is important not only for its commercial utility but also for understanding wood bond durability. Bulking modifications occupy space inside the cell wall, limiting the space available for water. We used two bulking modifications on yellow poplar (Liriodendron tulipifera L.): acetylation (Ac), which bulks and converts a wood hydroxyl group to an ester, while butylene oxide (BO) also bulks the wood but preserves a hydroxyl group. Both result in lower water uptake; however, the loss of the hydroxyl group with Ac reduces the wood’s ability to form hydrogen and other polar bonds with the adhesives. On the other hand, the BO reaction replaces a hydroxyl group with another one along a hydrocarbon chain; thus, this product may not be harder to bond than the unmodified wood. We investigated how these chemical modifications of wood affect bond performance with four adhesives: resorcinol-formaldehyde (RF), melamine-formaldehyde...
Southern pine solid wood (SPS) and fiber (SPF) were chemically modified to various weight percent gains (WPG) using either acetic anhydride (AA, 4%-19% WPG), butylene oxide (BO, 4%-23% WPG), or propylene oxide (PO, 6%-30% WPG). After...
moreSouthern pine solid wood (SPS) and fiber (SPF) were chemically modified to various weight percent gains (WPG) using either acetic anhydride (AA, 4%-19% WPG), butylene oxide (BO, 4%-23% WPG), or propylene oxide (PO, 6%-30% WPG). After modification, part ofthe specimens were extracted with a toluene:ethanol (2:1) solution for 2 hours or water leached for 2 weeks. The equilibrium moisture content (EMC) at 30%, 65% and 90% relative humidity (RH) and 27 °C was determined on all specimens. Laboratory soil block decay testing using the brown-rot fungus Gloeophyllum trabeum was performed and weight loss calculated. Two possible mechanisms for biological efficacy by chemical modification ofwood have been proposed. One involves lowering the cell wall moisture content below a level required for microorganism attack. The other involves modification ofthe substrate in such a way that the specific enzymatic reactions cannot take place. Results on solid wood indicate that as the EMC is lowered by ...
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...
moreThe 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.
Title, Category, Date Posted -or-Publication Year. ... Category: Journal Articles File size: 1242 kb(s) Abstract: Cellulose degradation by brown rot fungi, such as Postia placenta, is poorly understood relative to the phylogenetically...
moreTitle, Category, Date Posted -or-Publication Year. ... Category: Journal Articles File size: 1242 kb(s) Abstract: Cellulose degradation by brown rot fungi, such as Postia placenta, is poorly understood relative to the phylogenetically related white rot basidiomycete, Phanerochaete ...
Southern pine solid wood and wood fiber were reacted with acetic anhydride to various acetyl weight gains. The equilibrium moisture content (EMC) was determined on these specimens at 30%, 65% and 90% relative humidity (RH) and 27 °C. A...
moreSouthern pine solid wood and wood fiber were reacted with acetic anhydride to various acetyl weight gains. The equilibrium moisture content (EMC) was determined on these specimens at 30%, 65% and 90% relative humidity (RH) and 27 °C. A standard soil block decay test using the brown-rot fungus Gloeophyllum trabeum was performed and weight loss calculated. Two possible mechanisms have been proposed to explain the resistance of attack of brown-rot fungi on chemically modified wood. One involves the lowering of the cell wall moisture level below that needed for fungal attack. The second involves changing the configuration and conformation of the substrates by modification in such a way that the enzymes can not recognize the substrate. The data presented in this paper indicates that lowering the cell wall moisture level is the major mechanism.
There is little published scientific literature on the laboratory or field testing of wood-plastic composites (WPC) against termite attack. Therefore, the objective of this research was to investigate termite resistance (both laboratory...
moreThere is little published scientific literature on the laboratory or field testing of wood-plastic composites (WPC) against termite attack. Therefore, the objective of this research was to investigate termite resistance (both laboratory and field) of 5 different extruded WPC blends of 50% western pine wood flour (WF) and high-density polyethylene (HDPE), and untreated pine solid wood. The study included two unmodified control WPC blends (one with cut surfaces and one with plastic rich surfaces); one blend with 3% coupling agent (maleated polyethylene, MAPE); one blend with acetylated WF; and one blend with 1% ZB. These 3 modifications/treatments were chosen because (1) coupling agents are known to promote bonding between the plastic and unmodified wood fibers when added to WPCs; (2) acetylating the wood esterifies the hydroxyl groups, making the wood more hydrophobic, dimensionally stable, and biologically durable; and (3) ZB is a known fungicide and insecticide used in some commerc...
Heartwood extractives from Tectona grandis were investigated for antitermitic activities against Heterotermes indicola in laboratory experiments. Extractives were removed from wood shavings by soxhlet extraction using an ethanol: toluene...
moreHeartwood extractives from Tectona grandis were investigated for antitermitic activities against Heterotermes indicola in laboratory experiments. Extractives were removed from wood shavings by soxhlet extraction using an ethanol: toluene (2:1) solvent system. Termite feeding and mortality followed a concentration dependent response. The highest termite mortality occurred at an extractive concentration of 10 mg/ml. The calculated LC50 based on the concentration dependant response was 3.2 mg/ml. Extractives showed high repellency and antifeedant activity against H. indicola. Tests in which extractives were used to vacuum-pressure treat southern pine and cottonwood, showed that T. grandis extractives imparted resistance to these non-durable species. At the highest concentration of extractives tested, complete mortality was observed after termites were exposed to extractive-treated southern pine and cottonwood. Compared to solvent controls, minimum weight losses of 3.6 and 3.5% were obs...
Chemical modification of the hydroxyl groups of wood can improve the properties of wood by providing moisture and biological resistance, as well as dimensional stability. Southern pine solid wood was chemically modified to various weight...
moreChemical modification of the hydroxyl groups of wood can improve the properties of wood by providing moisture and biological resistance, as well as dimensional stability. Southern pine solid wood was chemically modified to various weight percentage gains (WPG) with epoxybutene (EpB, 8%-38% WPG). After modification, specimens were extracted with a toluene: ethanol (2:1) solution for 2 hours or water leached for 2 weeks. The equilibrium moisture content (EMC) at 30%, 65% and 90% relative humidity (RH) and 27 C was determined on all specimens. Laboratory soil block decay evaluations against the brown-rot fungus Gloeophyllum trabeum was performed and weight loss calculated by mass loss. Biological efficacy was found, and the biological resistance correlated with the lowering of the equilibrium moisture content, suggesting that the mechanism of efficacy was due to moisture exclusion. To assist in understanding the mechanism of effectiveness, small angle x-ray scattering (SAXS) and wide-...
The moisture and decay resistance of wood-plastic composites (WPCs) reinforced with extracted or delignified wood flour (WF) was investigated. Three different extractions were preformed: toluene/ethanol (TE), acetone/water (AW), and hot...
moreThe moisture and decay resistance of wood-plastic composites (WPCs) reinforced with extracted or delignified wood flour (WF) was investigated. Three different extractions were preformed: toluene/ethanol (TE), acetone/water (AW), and hot water (HW). Delignification (DL) was performed using a sodium chlorite/acetic acid solution. All WPCs specimens were made with 50% by weight HDPE and WF, first compounded using extrusion followed by injection molding. After preconditioning in water at 70 °C for 5 days, the specimens were exposed for 12 weeks to the brown-rot fungus, Gloeophyllum trabeum in the AWPA D1413 standard soil block test. The WPC made with untreated wood flour had the highest overall weight loss (24.9 ±3.6%), followed by the HW (22.3 ±4.6%) and DL (16.4 ±3%). The TE (7.8 ±0.8%) and AW (7.7 ±2.3%) had the lowest weight losses. WPC moisture content was monitored before and after decay. Cracking was observed in some blends after the preconditioning, which may explain the differe...
Although wood remains the building material of choice in residential construction, it has the deleterious properties of poor durability and dimensional instability. For aboveground exterior applications such as deck flooring, important...
moreAlthough wood remains the building material of choice in residential construction, it has the deleterious properties of poor durability and dimensional instability. For aboveground exterior applications such as deck flooring, important properties include hardness and weathering resistance. To improve these properties, wood was modified with acrylic polymers to slow the moisture sorption and improve its hardness and with a hybrid inorganic-organic thin film to improve its photostability. Modification of the wood was accomplished by in situ polymerization of acrylic monomers in the lumens and voids of the wood. Deposition of the hybrid inorganic-organic thin film in the cell walls of the outer layers of the wood was accomplished by sol-gel deposition from a water-borne sol of silsesquioxane oligomers. The weathering behaviour, including weight and colour changes of the coated and non-coated modified wood specimens under exposure to accelerated weathering conditions was performed in a ...
Evaluating the fungal durability of wood-plastic composites (WPCs) is complicated by the influence of slow moisture sorption. Recently, the American Wood Protection Association (AWPA) Standard Method E10, Testing Wood Preservatives by...
moreEvaluating the fungal durability of wood-plastic composites (WPCs) is complicated by the influence of slow moisture sorption. Recently, the American Wood Protection Association (AWPA) Standard Method E10, Testing Wood Preservatives by Laboratory Soil-Block Cultures, was modified to incorporate not only solid wood, but also wood-based composites and WPCs. To simulate long term WPC performance, conditioning of the specimens is now required prior to fungal exposure to increase the moisture content of the specimens. The moisture and fungal durability, as well as the mechanical properties, of two different WPCs were investigated in the laboratory following this new AWPA E10-12 Standard. Wood flour was modified with acetic anhydride and then extruded with high density polyethylene (HDPE). Wood flour was treated with an isothiazolone-based solution and then injected molded with polypropylene (PP). WPCs were conditioned by water soaking either 2 weeks at 22 ˚C or 5 days at 70 ˚C. Weight and...
Wood-plastic composites (WPC) contain wood fiber (or flour), thermoplastics and additives and are exposed to UV light, moisture, and biological deterioration in outdoor installations. Accelerated laboratory tests can help to predict the...
moreWood-plastic composites (WPC) contain wood fiber (or flour), thermoplastics and additives and are exposed to UV light, moisture, and biological deterioration in outdoor installations. Accelerated laboratory tests can help to predict the durability of WPCs, but long term evaluations are needed to validate these results. Field exposed above-ground WPC deck boards (30.5 x 139.7 x 609.6 mm) and in-ground (19 x 19 x 457 mm) stakes were visually evaluated near Saucier, Mississippi and Madison, Wisconsin over 17 years. Four blends were extruded on commercialscale equipment containing additives including colorant, light stabilizers, lubricant, and the fungicide zinc borate (ZnB). There are some difficulties evaluating the WPC materials compared to solid wood: in-ground stakes snap quite easily when removing them for inspection and decay is more difficult to determine because the WPC does not become soft. Differences in deterioration were seen between each test site: the in-ground deteriorat...
Neutron imaging is a nondestructive evaluation technique with enhanced hydrogen sensitivity that allows researchers to monitor water content and transport in materials. In lignocellulosic research, this technique has typically been used...
moreNeutron imaging is a nondestructive evaluation technique with enhanced hydrogen sensitivity that allows researchers to monitor water content and transport in materials. In lignocellulosic research, this technique has typically been used to measure changes in moisture content, water transport and even local changes in the density of wood. Yet, studies looking into the combined effects of moisture-uptake, chemical modifications and thermal degradation are still lacking. This is perhaps due to the inherent limited availability of these instruments and their lesser spatial resolution compared to X-ray imaging. While recent advances in detector technology and neutron production have led to continued improvements in both instrument availability and spatial resolution, the technique remains underutilized in forest products research. Here, we used thermal neutron imaging to measure differences in the attenuation of the neutron beam due to acetylation in both solid wood samples and wood−plas...
Neutron imaging is a nondestructive evaluation technique with enhanced hydrogen sensitivity that allows researchers to monitor water content and transport in materials. In lignocellulosic research, this technique has typically been used...
moreNeutron imaging is a nondestructive evaluation technique with enhanced hydrogen sensitivity that allows researchers to monitor water content and transport in materials. In lignocellulosic research, this technique has typically been used to measure changes in moisture content, water transport and even local changes in the density of wood. Yet, studies looking into the combined effects of moisture-uptake, chemical modifications and thermal degradation are still lacking. This is perhaps due to the inherent limited availability of these instruments and their lesser spatial resolution compared to X-ray imaging. While recent advances in detector technology and neutron production have led to continued improvements in both instrument availability and spatial resolution, the technique remains underutilized in forest products research. Here, we used thermal neutron imaging to measure differences in the attenuation of the neutron beam due to acetylation in both solid wood samples and wood−plas...
Neutron imaging is a nondestructive evaluation technique with enhanced hydrogen sensitivity that allows researchers to monitor water content and transport in materials. In lignocellulosic research, this technique has typically been used...
moreNeutron imaging is a nondestructive evaluation technique with enhanced hydrogen sensitivity that allows researchers to monitor water content and transport in materials. In lignocellulosic research, this technique has typically been used to measure changes in moisture content, water transport and even local changes in the density of wood. Yet, studies looking into the combined effects of moisture-uptake, chemical modifications and thermal degradation are still lacking. This is perhaps due to the inherent limited availability of these instruments and their lesser spatial resolution compared to X-ray imaging. While recent advances in detector technology and neutron production have led to continued improvements in both instrument availability and spatial resolution, the technique remains underutilized in forest products research. Here, we used thermal neutron imaging to measure differences in the attenuation of the neutron beam due to acetylation in both solid wood samples and wood−plas...
Chemical and morphological changes of incipient to advanced stages of palo podrido, an extensively delignified wood, and other types of white rot decay found in the temperate forests of southern Chile were investigated. Palo podrido is a...
moreChemical and morphological changes of incipient to advanced stages of palo podrido, an extensively delignified wood, and other types of white rot decay found in the temperate forests of southern Chile were investigated. Palo podrido is a general term for white rot decay that is either selective or nonselective for the removal of lignin, whereas palo blanco describes the white decayed wood that has advanced stages of delignification. Selective delignification occurs mainly in trunks of Eucryphia cordifolia and Nothofagus dombeyi, which have the lowest lignin content and whose lignins have the largest amount of beta-aryl ether bonds and the highest syringyl/guaiacyl ratio of all the native woods included in this study. A Ganoderma species was the main white rot fungus associated with the decay. The structural changes in lignin during the white rot degradation were examined by thioacidolysis, which revealed that the beta-aryl ether-linked syringyl units were more specifically degraded ...
Description: Wood is used to produce many products (structural and nonstructural) for applications in which its natural properties are adequate. With the decrease of wood availability and the increase of less durable, younger and...
moreDescription: Wood is used to produce many products (structural and nonstructural) for applications in which its natural properties are adequate. With the decrease of wood availability and the increase of less durable, younger and faster-growing trees, it is possible to modify wood in various ...
Towards ecology and economy harmonization of tropical forest resources : proceeding of the 6th International Wood Science Symposium LIPI - JSPS Core University Program in the field of wood science / organized by Research and Development...
moreTowards ecology and economy harmonization of tropical forest resources : proceeding of the 6th International Wood Science Symposium LIPI - JSPS Core University Program in the field of wood science / organized by Research and Development Unit for Biomaterials, ...
Although laboratory evaluations of wood-plastic composites (WPCs) are helpful in predicting long- term durability, field studies are needed to verify over all long-term durability. Field exposure can encom pass numerous degradations...
moreAlthough laboratory evaluations of wood-plastic composites (WPCs) are helpful in predicting long- term durability, field studies are needed to verify over all long-term durability. Field exposure can encom pass numerous degradations i.e., fungal, ultraviolet light, moisture, wind, temperature, freeze/thaw, wet/ dry cycling, termites, mold, etc. that traditionally are studied separately in the laboratory. Moisture sorption of WPCs is slower than in unmodified solid wood, but it affects the strength, stiffness, and ultimately the decay of the material. The objectives of this study were to: 1) investigate several methods of reducing moisture sorption and, consequently, fungal degradation, 2) compare the ef fects of moisture and fungal decay on woodflour-filled and woodfiber-reinforced high-density polyethylene, and 3) perform laboratory and field evaluations of WPCs specimens. The methods used to reduce mois ture were: 1) acetylation of the wood component and 2) use of a coupling a...
Although moisture sorption in woodfiber-thermo plastic composites (WPCs) is slower than in unmodified solid wood, it still affects strength and ultimately results in decay of the material in moist outdoor exposure condi tions. Chemical...
moreAlthough moisture sorption in woodfiber-thermo plastic composites (WPCs) is slower than in unmodified solid wood, it still affects strength and ultimately results in decay of the material in moist outdoor exposure condi tions. Chemical modification of the hydroxyl groups of wood with acetic anhydride esterifies the hydroxyl mak ing the wood more hydrophobic and dimensionally sta ble. Coupling agents are known to promote bonding be tween the plastic and unmodified wood fibers when added to WPCs. The objective of this study was to investi gate several methods of decreasing moisture sorption and, consequently, fungal degradation in WPCs. Three WPC blends were extruded into 3- by 12- by 90-mm speci mens: 1. � 50 percent high-density polyethylene (HDPE) and
The fungal resistance of high density polyethylene filled with 50% wood flour was investigated using laboratory soil block tests. Modifications to standard test methods were made to increase initial moisture content, increase exposure...
moreThe fungal resistance of high density polyethylene filled with 50% wood flour was investigated using laboratory soil block tests. Modifications to standard test methods were made to increase initial moisture content, increase exposure surface area, and track moisture content, mechanical properties, and weight loss over the exposure period. Mechanical properties decreased after 12 weeks exposure to Gloeophyllum trabeum and Trametes
ABSTRACT The degradable nature of high-performance, wood-based materials is an attractive advantage when considering environmental factors such as sustainability, recycling, and energy/resource conservation. The Handbook of Wood Chemistry...
moreABSTRACT The degradable nature of high-performance, wood-based materials is an attractive advantage when considering environmental factors such as sustainability, recycling, and energy/resource conservation. The Handbook of Wood Chemistry and Wood Composites provides an excellent guide to the latest concepts and technologies in wood chemistry and bio-based composites. The book analyzes the chemical composition and physical properties of wood cellulose and its response to natural processes of degradation. It describes safe and effective chemical modifications to strengthen wood against biological, chemical, and mechanical degradation without using toxic, leachable, or corrosive chemicals. Expert researchers provide insightful analyses of the types of chemical modifications applied to polymer cell walls in wood, emphasizing the mechanisms of reaction involved and resulting changes in performance properties. These include modifications that increase water repellency, fire retardancy, and resistance to ultraviolet