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The decay resistance of chemically modified aspen composites to the white rot fungus Coriolus versicolor (L.) Quelet
1998 - IRG/WP 98-40122
Chemical modification of Aspen wood (Populus tremula L.) in the form of solid wood, veneers and sawdust was undertaken by a two step procedure consisting of esterification with maleic anhydride (MA) and subsequent oligoesterification with MA and glycidyl methacrylate (GMA) or allyl glycidyl ether (AGE). Modified wood was thermoplastic and was thermally formed by hot-pressing to produce veneer or solid wood samples with smooth glossy surfaces, while plastic-like wafers were obtained by hotpressing modified sawdust. Chemical modification alone was shown to enhance the biological resistance of Aspen to decay by Coriolus versicolor. In addition, hot-pressing enhanced decay resistance of both unmodified wood and esterified wood veneer samples, although no improvement was found by hot pressing oligoesterified wood. The most effective treatment for the improvement of decay resistance was chemical modification of the sawdust in conjunction with hot-pressing. A microscopic examination of chemically modified and control samples following exposure to the fungus showed more extensive colonisation and decay in untreated, unpressed samples.
M C Timar, A J Pitman, M D Mihai


About the water and biological resistance of some new chemically modified wood composites
1997 - IRG/WP 97-40077
As well known, wood represents a valuable natural composite material with a very large utilisation as solid wood or in wood based composite materials. Its qualities but also its defects as the dimensional instability, the susceptibility to biological attack, the anisotropy, are due to its complex structure. Research has demonstrated that the chemical modification of wood, meaning the involving of its main chemical components through their reactive alcoholic hydroxyl groups in chemical reactions with different chemical reagents, can be a new way to ameliorate the wood or wood composites but also to obtain new wood based materials. The chemical thermoplasticization of wood, studied theoretically and experimentally by the Japanese researchers as Matsuda, Mori, Morita, Nakano, Shiraishi, Ueda seems to be a very interesting possibility. The paper presents the results of our experiments concerning the chemical thermoplasticization of wood through oligoesterification and the obtaining and characterisation of some products based on this type of chemically modified wood. In fact the main goals of this stage of the researches were: - the obtaining and characterisation of the thermoplastic wood; - the study of the thermoformation possibilities for the thermally flowable material obtained as sawdust; - the evaluation of the possibilities to carry out this chemical modification process as a surface treatment for solid wood; - the evaluation of the water and biological resistance for the obtained products.
M C Timar, M D Mihai, G Baciu


Leaching of chromium and other cca components from wood-cement composites made with spent CCA treated wood
2000 - IRG/WP 00-50153
Wood cement composites are an attractive option for recycling spent treated wood, since the CCA treatment enhances the physical, mechanical and biological resistance properties of the composite. However, we have noted a higher than normal leaching of chromium from these products and this appears to result from conversion of some of the trivalent chromium to the more leachable and toxic hexavalent chromium from the trivalent chromium in the wood. The effects of hexavalent chromium reducer --FeSO4, the pH value of mixing water and different kinds of accelerators on the leaching properties of this composite were tested. Arsenic and copper components of CCA in treated wood were well fixed after mixed with cement. Although total chromium leaching amount was reduced greatly in the CCA treated wood-cement composite compared to CCA treated wood, more hexavalent chromium was detected from the leachate of the composite. Cr+6 leaching accounted for about 80% of the total chromium leaching. FeSO4 had a positive effect on decreasing chromium leaching amounts, especially when used in the board having more potentially leachable chromium. Reducing the pH value of mixing water decreased the total chromium leaching amount, but its effect on Cr+6 leaching was not significant. The leaching of Cr+6 and total chromium also depended on the accelerators used; boards with added CaCl2 showed less Cr+6 and total chromium leaching amounts, while Na2CO3 increased chromium leaching.
D Qi, P A Cooper


Biocide Treatments for Wood Composites - A Review
2006 - IRG/WP 06-40323
This paper reviews the biocidal treatment of wood composites. Included are in-process and post-process treatments. Various biocides are covered as are methods of application. Novel treatments and technologies are also presented.
J W Kirkpatrick, H M Barnes


Ancillary properties of vapor boron-treated composites
2001 - IRG/WP 01-40210
This paper discusses the water absorption, thickness swelling, and internal bond strength of North American composites treated using a vapor boron treatment process. For oriented strandboard, high boron loadings led to lower internal bond strength and lower thickness swelling. Water absorption results were variable but no deleterious effect of treatment was noted. For medium density fiberboard, the highest loadings led to reduced internal bond strength. Thickness swelling decreased with increasing boron level, but not significantly. As with OSB, water absorption results varied.
W A Jones, H M Barnes, R J Murphy


Leachability of borate-modified oriented strandboard: A comparison of zinc and calcium borate
2002 - IRG/WP 02-40232
The leachability of boron in zinc and calcium borate-modified oriented strandboard (OSB) was investigated in this study. The leaching experiments were conducted by exposing edge-sealed OSB samples under running water for 8, 24, 72, and 216 hours. The results were compared with those from the unleached controls. Boron leaching of the modified OSB occurred upon the initial water exposure, and the leaching rate decreased as the leaching time increased. Borate type, initial BAE level, wood species, and sample thickness swelling significantly influenced the leachability. There was no consistent effect of polyethylene glycol (PEG) on zinc borate leaching. Calcium borate with a smaller particle size helped reduce its leachability. The glueline washing due to thickness swelling of the test samples under water and decomposition of the borate to form less water-soluble boric acid are thought to be two possible causes for the observed leaching. The relationship between assayed BAE and leaching time followed a decaying exponential function for zinc borate OSB and a Harris decaying power function for calcium borate OSB. The material constants of the regression models allow comparing leachability of the modified OSB for various wood species. A unified leaching method for treated wood composite materials is needed.
S Lee, Q Wu


Sustainability Through New Technologies for Enhanced Wood Durability. COST Action E37 – A New Action in the Forestry Domain
2004 - IRG/WP 04-40293
The main overall objective of the action is to concentrate on the contribution of wood durability on the sustainability through the development of systems for quality assurance and perfoamance of modified wood and wood products as alternatives to wood treated with traditional preservatives. By this means it seeks to improve and consequently increase the cost-effective use of sustainably produced European timber, wood-based fibre, and recycled raw materials. The action will seek to optimize methods for testing and characterizing durability performance against physical as well as biological factors. This will exploit relevant selected results from specific aspects of the preceding COST Action E22 on “Environmental optimization of wood protection” and in the EU thematic network for wood modification. It will also exploit specific achievements from COST Action E18 “High performance in wood coating”.
R-D Peek


Termite Response to Agricultural Fiber Composites: Hemp
2005 - IRG/WP 05-10548
Industrial hemp, Cannabis sativa, is a fiber usable in manufacture of nutritional products, rope, textiles, paper and building products. Due to the illicit recreational uses of Cannabis sativa varieties with high tetrahydrocannabinol content (marijuana), hemp is not grown commercially in the United States. However, it is grown in many other nations, and has been proposed as a replacement for sugarcane and other commodity crops in the United States, including Hawaii. These studies were undertaken to determine the susceptibility of several potential hemp building products to Formosan subterranean termite attack. Although advocates of the fiber sometimes comment on its relative resistance to insects and decay fungi, there is little to no data available to either substantiate or refute these claims. Termite responses to experimental hemp fibreboards (UF or MDI resins), and to a commercial mineralized hemp building material (Isochanvre) were evaluated in laboratory essays. The hemp fibreboards were readily attacked by termites, although the UF resin was relatively toxic to them in comparison to MDI. Termites also readily consumed the mineralized hemp fibers, although mortality was high. Thus, one can conclude that hemp is susceptible to termite attack. Urea formaldehyde resin in fibreboards and silica, lime or boric acid in mineralized hemp were detrimental to termite survival, but still did not prevent significant attack. Preservative or other treatments appear to be required to protect hemp building products from degradation.
J K Grace


Termite response to Agricultural Fiber Composites: Bagasse
2005 - IRG/WP 05-10549
Bagasse, or sugarcane rind, is a fibrous by-product of sugar extraction from sugarcane, Saccharum officinarum L. Bagasse fiber performs similarly to hardwood fiber in composite board products. In laboratory studies, Formosan subterranean termites survived as well on a diet of Bagasse as on Douglas-fir wood. Field tests with a compressed Bagasse panel (produced by heat extrusion) indicated that termites readily penetrated the acrylic/vinyl latex coating on the panel, and tunnelled throughout the interior Bagasse fibers. Treatment of the fibers with disodium octaborate tetrahydrate did not prevent the termite penetration of the panel exterior. Subsequent moisture sorption by the fibers led to rapid swelling and deformation of the panels. A dimensionally stable, high density Bagasse particleboard was also evaluated in laboratory tests. No swelling was noted, although the particleboard was readily penetrated and consumed by Formosan subterranean termites, and mold growth was also noted on the test wafers. In recent years, high-profile Bagasse board production facilities were opened in both Louisiana and Hawaii, only to close shortly thereafter. Bagasse may have more market potential in a value-added, preservative treated product than as a low-end commodity competing with comparable wood products.
J K Grace


Durability of Wood Plastic Composites Relative to Natural Weathering and Preservative Treatment With Zinc Borate
2005 - IRG/WP 05-40316
Wood-Plastic Composites (WPCs) used for decking have experienced dramatic increases in North America, averaging 25% growth per annum since 1998. A key factor contributing to this growth has been the successfully communicated message that they are "virtually maintenance free". The common perception being that the wood fiber is completely encapsulated by the thermoplastic resin, minimizing the potential for moisture absorption and inhibiting attack by wood destroying organisms. Recent publications, however, have raised concerns about the durability of WPCs. These studies showed that wood particles close to the surface of WPC products can attain moisture levels high enough to facilitate the onset of decay. Other experiments have shown that preconditioning this material through accelerated laboratory weathering (QUV) or natural exterior exposure to the elements, yielded significant increases in moisture uptake relative to the unexposed samples. The ability of these materials to absorb moisture has been identified as a significant factor in evaluating decay susceptibility in these laboratory tests. We examined moisture uptake in large sized (low surface to volume ratio) and smaller cut (high surface to volume ratio) WPC samples and found a much greater and rapid water uptake in the smaller samples. A soil block decay test with commercially produced unweathered WPC’s resulted in weight losses of between 10-20% (20-40% wood component) in as little as four months time. Effects of exterior weathering on moisture uptake showed increased moisture in samples taken from WPC boards in the field at various locations for 1 to 2 years. A soil block decay test with unweathered and naturally weathered WPCs showed significantly high weight loses in samples that had been in an outdoor exposure in Valencia, Ca for 2 years. Samples from the same exposure test that had been treated with 1.0 or 2.0 % zinc borate showed almost no weight loss.
M E Mankowski, F M Ascherl, M J Manning


Wood-based composites exposed to fungal degradation: Laboratory results
2001 - IRG/WP 01-40215
Oriented strandboard (OSB) and laminated veneer lumber (LVL) are widely used as residential construction materials. The durability of OSB and LVL against biological degradation has not been studied comprehensively. The objective of this research was to investigate the durability of OSB and LVL when exposed to wood decay fungi. Fourteen brown-rot and eight white-rot wood decay fungi were screened for their capacity to degrade OSB and LVL. Samples were evaluated for decay by weight loss measurements using the American Society for Testing and Materials D1413-76 soil block test method. Results revealed that the brown-rot fungus Gloeophyllum trabeum (Mad-617) and the white-rot fungus Trametes versicolor (Mad-697) degraded OSB to a greater extent than solid southern yellow pine wood. Both fungi degraded LVL to a much lesser extent than OSB. Our findings provide valuable information on the durability of OSB and LVL, to predict serviceability and protection requirements of these construction materials.
V W Yang, B Illman, L A Ferge, R J Ross


Bending & tensile properties of vapor boron-treated composites
2002 - IRG/WP 02-40228
North American composites including laminated veneer lumber, oriented strandboard, and medium density fiberboard were treated by vapor boron technology and subsequently tested in static bending. Tensile properties were also determined for the two composite boards. The study was designed as 3 x 2 factorial with three treatment levels and two mill locations for each composite type. In general, mill location significantly affected most property values while treatment level caused significant reductions at the highest treatment level only. The significance of mill location was taken to mean a significant difference due to species as species varied between locations for each composite type.
H M Barnes, R J Murphy, B K Via


Evaluation of chlorpyrifos and fungicides alone and in combination for control of insects and fungi in wood and wood composites
1998 - IRG/WP 98-30187
Wood composites are rapidly being adapted for use in exterior applications. The incorporation of a preservative system to prevent fungus and insect attack is necessary with most exterior composites. Research studies were reviewed pertaining to organic preservative systems based on Lentrek* insecticide wood treatment which contains the active ingredient chlorpyrifos alone and in combination with tebuconazole and propiconazole (fungicides) for use as a combination treatment preservative system for solid wood and wood composites. Effective retentions for chlorpyrifos for protection of wood from termite and beetle attack was determined to be 0.2 kg/m3 set by the high retentions needed for field control of Coptotermes formosanus. In addition, this retention also provides effective control of the termites; Coptotermes lacteus, Reticulitermes flavipes, and Nasutitermes exitiosus, and the Lyctiid powderpost beetle, Lyctus brunneus. Retentions needed for control of Gloeophyllum trabeum (brown rot) and Trametes versicolor (white rot) were determined to be 0.11 kg/m3 and 0.06 kg/m3 for tebuconazole and propiconazole, respectively. Discussions with the manufacturers of tebuconazole and propiconazole indicated that the two fungicides work best together when in a 1:1 ratio. Given the need for the 1:1 ratio then, retentions needed for the tebuconazole and the propiconazole for treatment of wood composites are therefore 0.1 and 0.1 kg/m3, respectively, using tebuconazole as the benchmark. Tebuconazole and propiconazole retentions of 0.08 and 0.08 kg/m3, respectively, afforded moderate stain and mold protection of treated wood with a 64% reduction in stain and mold coverage by 3 weeks; thereafter, protection diminishes with time to a 40% reduction in coverage by 8 weeks. Overall, the retentions needed for a mixture of tebuconazole/propiconazole/chlorpyrifos (T/P/C) for use in wood composites are 0.1/0.1/0.2 kg/m3, respectively, to protect the wood from attack by insects and decay fungi while at the same time providing some moderate reduction of stain/mold coverage. Also, in order to compensate for the anticipated long term degradation of the two fungicides under field conditions, the fungicide retentions were increased by 50% thereby resulting in final recommended retentions for use of T/P/C in wood composites as 0.15/0.15/0.2 kg/m3, respectively.
M P Tolley, P E Laks, R Fears


Resistance of wood inorganic material composites against decay fungi and subterranean termites
1996 - IRG/WP 96-40062
Double diffusion process was applied to the treatment of small sound sapwood specimens [20(T) x 20(R) x 10(L) mm³] of Cryptomeria japonica D. Don. The specimens were consecutively dipped in the two kinds of acqueous solutions to form water insoluble deposits within the wood after an expected reaction between the solutes. Following the comparison of deposits formed and treating conditions (temperature and solution concentrations), BaHPO4 as a water insoluble precipitation performed best against decay fungi (Coriolus versicolor and Tyromyces palustris) and subterranean termites (Coptotermes formosanus Shiraki) in the standardized laboratory tests. Addition of boric acid enhanced the performance of the wood inorganic material composites. Relatively low weight percent gain by deposits (<3%) was proved effective in controlling biological deterioration of the treated samples when boric acid was added to the treating solutions
K Tsunoda, T Yoshimura, M Takahashi, S Hirao, H Usui


Modèles de laboratoire et évaluation des risques. Protocole pour l'étude physiqo-chimique et toxicologique de la thermolyse de bois, de matériaux composites et de végétaux arbustifs
1995 - IRG/WP 95-50040-03
Thermolysis of samples is achieved inside an oven called "Fire model", designed to simulate fire conditions. This fire model was previously designed by the LEMD at the occasion of studies carried out for the purpose of toxicity studies on materials in the conditions occurring at the building level. This model essentially a cubic chamber takes into account the energy of radiation reflexed on the walls in order to meet these building conditions. It is therefore close to the mathematical model with 2 zones of actual fires proposed by the National Bureau of Standards. In that NB Model, a convective heath released by a given source reaches very rapidly the ceiling, but a radiative energy is sent rewards to the bottom, which has the result to give a part of the calories to back to the source. The hot exhaust gases are release at the top, which ensures convection and defines therefore two zones of temperature in the chamber. This model was applied to a series of wooden construction lumber, composites and bush plants.
R Capron, E Leghouchi, M Guerbet, E Dittmar, J M Jouany


Physical and mechanical properties of wood-polymer composites prepared from alder wood (Alnus glutinosa (l.) gaertn. subsp. barbata (c.a.mey.) yalt)
2001 - IRG/WP 01-40201
In this study, the physical mechanical properties of wood-polymer composites prepared from alder (Alnus glutinosa (L.) Gaertn. subsp. barbata (C.A.Mey.) Yalt) wood were investigated. Three different monomers styrene, methyl methacrylate and styrene/methyl methacrylate (70/30) mixtures and two loading levels were used in preparation of wood-polymer composites. Of physical properties, the oven-dry specific gravity, the ratio of water uptake, the water repellent effectiveness and from mechanical properties; the compression strength parallel to the grain were determined. Full loading applications gave the best results for all monomer. The oven dry specific gravity, the water repellent effectiveness and, the compression strength parallel to the grain were found between 0.710-0.950 gr/cm3, 39.45-85.78% and 338.78-645.13 kp/cm2 respectively.
A Temiz, Ü C Yildiz, E D Gezer


Future Directions Regarding Research on the Environmental Impacts of Preservative-Treated Wood: Environmental Impacts of Preservative-Treated Wood. February 8-11, 2004, FL, USA Workshop – Research Needs
2004 - IRG/WP 04-50222
This paper presents a series of documents that focus on research needs for potential future work focusing on the environmental impacts of preservative-treated wood. These documents were developed through a conference sponsored by the Florida Center for Environmental Solutions (FCES), located in Gainesville, Florida. The conference was held in Orlando, Florida, February 8 – 11, 2004 and the title of the conference was, “Environmental Impacts of Preservative-Treated Wood.” Approximately 150 people from 15 countries attended the conference. The “research needs” documents developed to date were summarized from: 1) feedback received from conference participants prior to the conference and 2) a two hour workshop held at the conclusion of the conference. A draft voting ballot has been prepared from these documents. This ballot is currently being reviewed by the FCES conference Technical Advisory Committee and a final ballot will be released in mid-April for a vote among the conference participants. A copy of the draft voting ballot is included at the end of this document. Results of the vote will be released at the 35th Annual IRG Meeting in Slovenia.
H M Solo-Gabriele, J D Schert, T G Townsend


The Protection of Wood with Oxy-aluminium Compounds
2002 - IRG/WP 02-30286
Wood inorganic composites (WICs) containing aluminium compounds were developed and tested in relation to some essential requirements of preservative treated wood. Four different oxy-aluminium treatments were developed and identified according to the final insoluble compounds formed (sodium aluminate, aluminium hydroxide, magnesium aluminate and aluminium borate) in wood. Vacuum impregnation or double diffusion were used as delivery systems for the chemicals. Higher weight percent gains were obtained when wood was treated by vacuum impregnation. Inorganic deposits were detected throughout the structure of treated wood using scanning electron microscopy. A high degree of dimensional stability was imparted to Scots pine by the treatments, and significant dimensional stability was retained even after treated wood was subjected to cold-water leaching. The oxy-aluminium treatments did not, however, impart water-repellency to wood. The decay resistance of oxy-aluminium treated wood, which was assessed through the use of terrestrial microcosms, was dependent on treatment, soil type and temperature, and exposure times. Oxy-aluminium treated wood showed increased resistance to brown rot. Sodium aluminate and aluminium hydroxide were more effective than magnesium aluminate and aluminium borate in protecting wood against soft rot. The results suggest that it is possible to protect some important wood properties with the use of oxy-aluminium compounds. Further research is needed to fully explore the potential of oxy-aluminium treatments for the protection of wood.
F A Ximenes, P D Evans


Applicability of supercritical carbon dioxide to the preservative treatment of wood-based composites
2001 - IRG/WP 01-40199
Treatability of five structural-use wood-based composites (medium density fiberboard, hardwood plywood, softwood plywood, particleboard and oriented strand board) was evaluated when supercritical (SC) carbon dioxide (CO2) was used as a carrier solvent. Treatments were conducted at three temperature 32 levels (25, 35 and 45°C) and two pressure levels [80 kgf/cm2 (7,845 kPa) and 120 kgf/cm2 (11,768 kPa)]. Although small changes in weight and thickness of the wood-based composites were caused by treatments with SC-CO2, all treated materials did not sustain any physical damage. These results suggest that the treatment conditions provided the immediate penetration of SC-CO2 into the wood-based composites without any critical pressure gradient between outer and inner zones. Strength properties of the treated wood-based composites significantly improved after treatments in most cases. In contrast, a remarkable drop in strength properties occurred in oriented strand board specimens. Further studies are underway to determine the optimum treatment conditions using biocides incorporated into the mixing or treating vessel.
M Muin, A Adachi, K Tsunoda


Mobility of zinc borate wood composite preservative
1997 - IRG/WP 97-30153
Zinc borate (ZB) is being used as an antifungal and insecticidal wood preservative for flake/strand-based composites. Data is reported on the laboratory and field leaching behavior of ZB when contained in apen flake composites. In general, the performance results correlate with leaching hazard. Although the boron in ZB is more resistant to depletion than in sodium borates, the ZB boron will deplete over time under severe leaching conditions. In climates and/or exposures with higher leaching hazard, more depletion and corresponding fungal/insect attack is observed. The zinc component of ZB is much more resistant to depletion, but does not contribute as much to the preservative efficacy. Some depletion data indicates that a "reservoir" effect can occur, where boron from regions with a high ZB loading diffuses into regions of the test specimen with low loadings due to depletion. The good level of performance under these test conditions continues to support the use of ZB in protected exterior wood composite applications.
P E Laks, M J Manning


Preservative treatment of wood-based composites with a mixture formulation of IPBC-silafluofen using supercritical carbon dioxide as a carrier gas
2003 - IRG/WP 03-40251
Wood-based composites treated with a mixture formulation of a fungicide, 3-iodo-2-propynyl butylcarbamate (IPBC) and a termiticide, silafluofen using supercritical carbon dioxide (SC-CO2) as a carrier solvent were tested for their resistance to decay and termite attack in the laboratory. The treatment solution was prepared by mixing both biocides (IPBC 10 + silafluofen 1) with a co-solvent, ethanol to have an identical ratio of each constituent in the commercial formulation for superficial treatment of wood. SC-CO2 treatments were conducted at 35oC/7.85 MPa, 35oC/9.81 MPa and 55oC/11.77 MPa with a direct introduction of the biocidal solution into the treatment vessel where specimens (210 x 30 mm x thickness) of medium density fiberboard, hardwood plywood, softwood plywood, particleboard and oriented strand board were placed. Laboratory tests were conducted with the treated materials according to Japanese standard methods. Results of laboratory tests indicated that the current treatment conditions significantly enhanced the resistance of the treated wood-based composites against fungal and termite attacks. Comparison with the results obtained for wood-based composites treated with an individual biocide showed that treatment with a mixture would not cause any negative effect to the efficacy of each biocide, although the amount of each constituent in a mixture formulation must be carefully decided to provide wood-based composites with a satisfactory performance against any biological degradation when SC-CO2 is used as a carrier solvent.
K Tsunoda, M Muin


Resistance of two commercial cement-bonded rubberwood particle composites to decay and termites
2000 - IRG/WP 00-10338
Two types of cement-bonded rubberwood (Hevea brasiliensis) particle composites (tradenames: Cemboard and Primaflex in Malaysia), were evaluated for termite resistance (prevalent termite: Coptotermes curvignathus) in the field, and decay resistance (test white rot fungi: Schizophyllum commune and Pycnoporus sanguineus; test brown rot fungus: Gloeophyllum trabeum; test soft rot fungi: Phialophora fastigiata and compost-Chaetomium globosum mixed inocula) in the laboratory. Three termite- or decay- susceptible wood materials [rubberwood, kempas (Koompasia malaccensis) and radiata pine (Pinus radiata) pressed pulp] were also included for comparison. Both types of wood-cement composites were consistently shown to be immune to decay fungi and subterranean termites, recording also much lower final moisture contents of the composites compared with rubberwood, kempas and radiata pine pressed pulp. These wood-cement composites are therefore suitable for use in a severe decay and termite hazard.
A A H Wong


Preservation of wood composites with zinc borate
1995 - IRG/WP 95-30074
Inorganic borates such as boric acid, borax, disodium octaborate tetrahydrate, and zinc borate can be incorporated into wood composites such as waferboard to impart decay and insect resistance to the final product. Zinc borate is especially well suited for this application due to its efficacy and leach resistance. The paper summarizes the work performed to date in this area. The effects on strength properties of the composite, water leach resistance of the borate, and effectiveness of the preservative treatment depends on the properties of the borate used and manufacturing variables such as adhesive type and content. In extensive work evaluating the properties of aspen waferboards bonded with pMDI adhesive, we have found that zinc borate performs well as a preservative additive. Such composites have excellent strength and water properties, as well as decay and termite resistance when appropriate levels of adhesive and borate are used. Further work is currently underway to evaluate the performance of zinc borate containing waferboard systems in severe ground contact applications. These types of products might be used in applications traditionally reserved for pressure treated solid wood and plywood.
P E Laks, M J Manning


Durability of Wood/Plastic Composites Made From Parthenium species
2002 - IRG/WP 02-40225
Previous study indicated that the natural chemical constituents of the guayule plant (Parthenium argentatum) improved some durability properties of wood when it was treated with resin extracted from guayule. At present, there are about a dozen species of Parthenium growing in the North American continent. P. argentatum is the only species with harvestable amounts of the rubber latex. Other species such as P. incanum and P. tomentosum produce primarily resinous materials, but which could be as useful as the P. argentatum species for making composites. The predicted commercialization of guayule for its hypoallergenic latex will result in a significant amount of waste plant material or bagasse that can be put to use in making wood products and would otherwise be a disposal problem. Thus, the guayule fiber residues can be a source of natural wood preservative to improve the durability of wood/plastic composites. Preliminary laboratory tests were conducted to determine the resistance of wood/plastic composites made from three Parthenium species against Eastern subterranean termite. The physical properties of these three types of composites were also measured, namely dimensional stability (water absorption, thickness swelling, two-hour boil, and linear expansion), and the strength properties such as bending and internal-bond (IB) or tensile stress perpendicular to face. The results were compared with a wood/plastic composite made from the commercial pine wood flour or fibers.
P Chow, F S Nakayama , J A Youngquist, J H Muehl, A M Krzysik


The durability of wood polymer composites against fungi and insects
2000 - IRG/WP 00-40161
New materials such as wood polymer composites are used more in France. These materials are obtained by mixing wood and thermoplastics in different ratios. These kind of material must be considered as new materials and some characteristics such as durability must be evaluated for outdoor applications. On the other hand, some recycled fibers from wood waste could be used as raw materials. Some woodpolymers have been made in order to prepare some profiles by extrusion process. The wood species used as reinforced materials are beech, spruce, jaboty and limba. The thermoplastics used are recycled polyvinylchloride, polyvinylchloride and polypropylene. The mechanical and physico-chemical properties of some profiles have been characterised. The durability of these wood polymer composites has been evaluated. Significant results on durability against wood-decaying fungi and insects as termites are presented.
G Labat, I Le Bayon, J Gerard, F Amin


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