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Effects of various preservative treatments on the mechanical and physical properties of plywood
1993 - IRG/WP 93-40007
The technical properties of plywood are related to both the intrinsic characteristics of its composing wood species and the quality and performance of the glue bond which acts as an interface between veneer sheets. Consequently mechanical and physical testing and glue bond strength analysis offer an appropriate means for studying the effect of preservative treatments on the overall quality of plywood. A range of boards was treated with waterborne and oilborne preservatives. Changes in modulus of elasticity, modulus of rupture and tensile strength were noted as well as variations in physical properties. Analysis of the glue bond strength was done by shear strength testing and determination of the amount of wood failure after different ageing procedures.
J Van Acker, M Stevens

Resistance to soft rot of hardwood plywood treated with CCA salt
1983 - IRG/WP 3258
Plywood made from indigenous hardwoods was treated at an average loading of 34 kg Celcure A per m³ and was installed in a field test. After 20 years the samples were only slightly attacked by soft rot and the glue bonds were still intact.
R S Johnstone

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

A Preliminary Report on the Properties of Engineered Wood Composite Panels Treated with Copper Naphthenate
2005 - IRG/WP 05-40294
This paper reports on our preliminary investigation of the properties of randomly oriented strandboard which had waterborne or powdered copper naphthenate (CuN) incorporated into the board during manufacture. When compared to zinc borate-treated controls (ZnB), the mechanical properties of strandboard (MOR, MOE, work-to-maximum load, internal bond strength) were not adversely affected by treatment with either form of copper naphthenate. In general, values for mechanical properties followed the trend untreated controls > waterborne CuN = powdered CuN > ZnB. Water absorption and dimensional properties followed a similar trend. This preliminary study suggests that CuN is a viable alternative treatment for engineered wood composites.
J W Kirkpatrick, H M Barnes

Decay Resistance and Bonding Properties of Structural Flakeboard
2002 - IRG/WP 02-40233
Experimental structural flakeboard panels consisting of differing furnishes and resins were produced and tested for internal bond, linear expansion, thickness swell, and decay resistance. One group of panels was produced with recycled CCA-treated wood as the furnish and commercial phenol formaldehyde (PF) resin as the binder. Other groups of panels were produced with either mixed hardwoods or southern pine as the furnish and then sprayed with a co-reacted soy-flour PF resin or a commercial face or core resin. The recycled CCA-treated panels contained 5 different furnish ratios (0:100, 25:75, 50:50, 75:25, and 100:0) of recycled CCA-treated southern pine and virgin, untreated southern pine. Tests on the panels bonded with co-reacted soy flour PF indicated that 30% substitution of phenol with soy flour in the resin system did not appreciably promote decay or reduce IB strength. As expected, panels produced with a higher ratio of recycled CCA-treated wood furnish, were generally subject to less weight loss during decay tests for brown rot (Gloeophyllum trabeum, ATCC 11539) and white rot (Trametes versicolor, ATCC 42462) but yielded lower IB values. Research in currently in progress to assess the resistance of all the aforementioned panel types to the Formosan subterranean termite (Coptotermes formosanus Shiraki).
T F Shupe, Chung-Yun Hse

Relationship between bond strength and surface characteristics of CCA-treated Douglas-fir
1993 - IRG/WP 93-30008
Chromated-copper-arsenate (CCA) treated Douglas-fir was laminated using a commercial phenol-resorcinol resin. CCA treatment enhanced the water repelleney of wood espeeially in the presence of extractives. However, the shear strength of CCA treated wood was 12% lower in dry condition and 38% lower in wet condition after six cycles of vacuum-pressure test than that of untreated wood. Slight removal of treated wood surface by planer or sander contributed for better adhesion, although it was not enough. The characteristics of treated wood surface was analyzed by X-ray photoelectron spectroscopy (XPS). CCA treatment increased C1 (C-H) and decreased C2 (C-OH), indicating migrated exctractives have enhanced the water repelleney of treated surface. The removal of hydrophobic surface of CCA-treated wood decreased C1 component of C1s spectra on the new surface.
K Yamamoto, J N R Ruddick

Effect of vapour boron treatment on mechanical properties of wood based board materials
1992 - IRG/WP 92-3727
The mechanical properties of Medium density fibre board, Chipboard and Oriented strand board were investigated after treatment to two retention levels of boric acid applied as a vapour phase system. A range of mechanical properties were investigated. The vapour boron treatment does not have any significant effect on most of the mechanical properties of the boards. The exception is a reduction in impact strength especially at the higher retention level.
R Hashim, D J Dickinson, R J Murphy, J Dinwoodie

A study of poplar LVL durability improvement:
1999 - IRG/WP 99-40148
The aim of this study was to optimise the durability of LVL panels by adding boron during the gluing process. Poplar veneers (2,6 mm thickness ) were selected by ISORY a French company . Two types of glue were tested : Phenol resorcine and Melamine Urea Formaldehyde. Each of them was mixed with various concentrations of borax (for the first one) and Boric acid(for the second one). Mechanical properties of final panels and bond strength properties were studied. LVL boron retention was tested after leaching. Influence of glue bonds on leaching was evaluated. The level of boron diffusion in wood was measured by spectrocolorimetry (CIELAB system). Our results have demonstrated that such treatment may improve efficiently LVL durability. Around 0.8% of boron was still fixed in our best panels after leaching tests. This kind of treatment appears to be a good alternative to improve durability of LVL Panels built with low resistant wood species.
B Charrier, V Bridaux, N Fauroux, F Charrier

The lasting dehydration of wood treated by bifluorides worked up in Diffusec noticed by a continual drying of the wood
1999 - IRG/WP 99-30196
After an immersion of sound wood in a solution of Diffusec, in which a combination of acid potassium and ammonium bifluorides = FHF- in dissociated form is present, their potassium and ammonium fluoride ions together with the bifluoride ion = (FHF-) diffuse into the wood. They make use of the woodmoisture available as O-H-O bonds directly attached to the cellulose in the wood fibres to attract the dissociated ions, which after fusion are replaced by F-H-F bonds. If any substance that contains ions or centers of electric charge (from polar bonds) is brought into contact with water, sufficient electrical disturbance result in rupture of the hydrogen bonds. This means that the hydrogen bonds in water are readily broken. The released water dipoles are then attracted to these charge centers. Acid fluorides, as F- and FHF-, act permanently as F-H-F bonds upon OH groups of the cellulose. They are able to gather from the "watercoating" which surrounds the OH groups, so to speak thin layers which leave the wood in the form of vapour. Besides that they are able to occupy the vacant places. Near it watermolecules of the outer layers will easier release as those ones more directed inside. The uptake of the hydrogen in the air is dependent of the RH uptill air-dry wood is reached with the EMC belonging to it. No thermic intervention is necessary according to prof. dr. J. B. van Duijneveldt.
H F M Nijman

Wood cement composites using spent CCA treated wood
1999 - IRG/WP 99-50126
The feasibility of using spent or out-of-service CCA treated wood as a component of wood/cement composites was evaluated. Cold pressed wood particle cement boards were made using CCA treated particles from a red pine (Pinus resinosa Ait.) pole removed from service and from untreated red pine wood from a new pole. Boards were manufactured using a range of wood to cement ratios and water to cement ratios. After curing the boards were evaluated for bending strength and stiffness, internal bond strength, water absorption, thickness swell, decay resistance and CCA leaching properties. The inclusion of CCA treated wood in the composite resulted in improved physical and mechanical properties compared to board made with untreated wood. There was also evidence of improved decay resistance in boards with spent CCA treated wood. Arsenic and copper leaching losses were very low from the wood cement composite compared to leaching from equivalent amounts of CCA treated wood. However, chromium leaching rates were not reduced.
Chen Huang, P A Cooper

Eco-Friendly Composites from Bagasse and Soy-based Resin
2009 - IRG/WP 09-40462
In this study, bagasse and soy-based resin were used for producing composite materials. The objective of this study was evaluation of some physical and mechanical properties of boards made of various ratios (100:0, 60:40, 40:60 and 0:100) of bagasse to wood fiber mixtures (wt: wt) with addition of Soy/PF resin at three levels (4, 8 and 10%) and 1.5% wax. All properties were tested according to ASTM D-1037 and all data were analyzed statistically. The results showed that by increasing bagasse fibers all properties of boards were deteriorated but by addition of 10% soy/PF resin all of them were improved significantly. Boards made of 40:60 ratio of bagasse to wood fiber mixtures and 10% Soy/PF resin content have acceptable bending strength and those are made of 100% bagasse and 10% Soy/PF resin content meet the requirements set for internal bond strength of the ANSI 208.2-1994 for interior uses.
G Rassam, B Jamnani

Effect of borax-boric acid Treatment of simul (Bombax ceiba) Veneers on Glue-Bond Quality of Plywood
2010 - IRG/WP 10-40525
The glue-bond quality of plywood made of treated simul (Bombax ceiba) veneers was investigated. The veneers were treated with cold and hot water solution of borax-boric acid (BB) of different concentrations and treatment durations. The plywoods were made at three different pressures in hot press using urea formaldehyde glue. The glue-bond strength of untreated plywood in dry shear-test was found to be 2.17 and 2.29 N/mm2 made at 1.05 and 1.40 N/mm2 pressure respectively. It was observed that the values of load at failure of treated plywood in dry shear-test gradually decreased with the increasing treatment duration and concentration of solution. Comparison of the bond strength of untreated plywood with the treated ones made with urea formaldehyde glue showed that all the treatment combinations lowered the bond quality. It was also found that 10% BB solution and highest treatment duration (3 for cold water days and 60 minutes for hot water) lowered the bond strength of the plywood which met ‘B-grading’ requirement. However, the values of glue bond strength in all other BB treated plywood met ‘A-grading’ requirement for gluing. It may be due to the highest percentage of chemical deposition within the cell wall structure lowered the bond quality. For all the treatments, low values of shear strength were observed in plywood made of hot water-treated veneer compared to that of cold water.
K Akhter, Md Abul Hashem, S Akhter

Glue-bond strength of simul (Bombax ceiba) plywood made of Neem (Azadiracta indica) leaves treated veneers
2013 - IRG/WP 13-40647
The glue-bond qualities of plywood made of treated simul (Bombax ceiba) veneers were investigated. The veneers were treated with cold and hot water solution of neem (Azadiracta indica, A. Juss.) leaves of different concentrations and treatment durations. The plywoods were made at three different pressures in hot press using urea formaldehyde glue. The glue-bond strength of untreated simul plywood in dry shear-test were found to be 2.17 and 2.29 N/mm2 made at 1.05 and 1.40 N/mm2 pressure respectively. It was observed that the glue-bond strength of neem leaves cold water treated (1:10) simul plywood in dry shear-test were 2.01 to 2.29 N/mm2 made at 1.05, 1.40 and 1.76 N/mm2 pressure. It was found that the values of load at failure of treated simul plywood in dry shear-test were gradually decreased with the increasing treatment duration and concentration of solution. For maximum treatments, lower values of shear strength were observed in plywood made of hot water-treated veneer compared to that of cold water-treated veneer. However, the values of glue bond strength in all Neem Leaves (NL) treated plywood met ‘A-grading’ requirement for gluing.
K Akhter, M A Hashem, S Akhter

The influence of log soaking temperature and thermal modification on the properties of birch veneers
2016 - IRG/WP 16-40749
In veneer manufacture the logs are routinely soaked in heated water baths in order to soften the wood prior to peeling. The temperature of the water may vary greatly between batches; however, the influence of log soaking temperature on veneer properties has had little research attention. Uncontrolled moisture is known to cause problems in wood-based materials, while thermal modification offers a method to control the interaction between wood and water. Therefore it might be beneficial to utilise thermally modified veneers in plywood manufacture. Yet, thermal modification is expected to also change other wood properties which might influence the possibility to utilise thermally modified veneers for wood-based-panels. The purpose of this study was to investigate the influence of log soaking temperature (70 °C and 20 °C) and thermal modification (8h in steam conditions) on selected properties of birch veneers, which are relevant in plywood manufacture. The surface area and surface free energy was studied with inverse gas chromatography (IGC). The surface free energy was found to be slightly higher for the unmodified veneers, however, no major difference was found in the dispersive part of the surface free energy between the log soaking temperatures or between unmodified or thermally modified veneers. The wetting of the veneers was investigated with the Wilhelmy plate method utilising the multicycling technique. It was found that lower log soaking temperature produced veneers with more hydrophobic nature. Also, thermal modification increased the hydrophobicity of the veneers. The bond strength was measured with an automatic bond evaluation system (ABES) using phenol formaldehyde (PF) resin. In general, the lower log soaking temperature resulted in slightly higher bond strength (however, the result was statistically insignificant), while thermal modification slightly lowered the bond strength. Based on these initial results thermally modifying the veneers prior to plywood manufacture might be useful.
S Källbom, K Laine, M S Moghaddam, A Rohumaa, K Segerholm, M Wålinder

Effect of Furfurylation on Shear Strength of Bond Line and Screw Withdrawal Resistance of Beech and Fir Wood
2016 - IRG/WP 16-40757
The aim of this study was to investigate the effects of furfurylation on shear strength of bond line and screw withdrawal resistance of beech (Fagus orientalis) and fir (Abies alba) species. In this regard, specimens with two different values of furfurylation i.e. low (fir 14% and beech 20%) and high (fir 38% and beech 65%) levels were prepared and evaluated in comparison with untreated specimens. The furfurylation was performed after impregnating the specimens by furfuryl alcohol under vacuum condition followed by heating duration to complete polymerization and crosslinking. Specimens were prepared according to standard ASTM D 905 in order to assess shear strength of bond line formed with three different types of adhesives, single-component polyurethane, polyvinyl acetate as well as urea-formaldehyde. Also screw withdrawal resistance of wood polymer specimens was measured perpendicular to grain and parallel to grain. The results indicated that the shear strength of the bond line decreased and screw withdrawal resistance increased by furfurylation level. Examination of adhesion mechanism demonstrated that formation of an appropriate interface between water-soluble adhesives and wood-polymer involves effective penetration of adhesive into cell wall. Hence, the interface of adhesives and material would be the determining factor in developing strength of adhesive joints. Since the wood-furfuryl alcohol is a cell-wall wood-polymer, the possibility of creating an appropriate interface by increasing of furfurylation level was impaired. On the other hand, the adhesion mechanism of polyurethane glue compared to water-soluble adhesives such as polyvinyl acetate and urea-formaldehyde is significantly different, therefore exhibited more strength. The withdrawal screw resistance of furfurylated wood was increased by furfurylation level due to changing nature of wood and increasing shear strength of wood-polymer. This gain was also more evident in fir than beech. The results showed that screw withdrawal resistance perpendicular to grain was higher than parallel to grain.
A Talaei, H Abdolzadeh, M Saleh Zare

The Resistance of Some Commercially Thermally Modified American Hardwoods to Termites and Fungi
2022 - IRG/WP 22-40944
Thermally Modified Wood (TMW) is now being produced in the United States but there are few data on the durability of these materials. In this study, commercially-produced thermally modified yellow poplar (Liriodendron tulipifera), red maple (Acer rubrum), and white ash (Fraxinus americana) were evaluated for fungal and termite resistance. The resistance of the three TMW species against Gloeophyllum trabeum (a brown-rot), Trametes versicolor (a white-rot) and Reticulitermes flavipes (native US subterranean termites) were evaluated using standard laboratory tests. In the decay test, an extra set of samples was prewetted prior to installation into the test to determine if slow wetting of the thermally modified samples contributes to apparent decay resistance. The decay test was only partly successful, but the results suggest that TMW is relatively durable, and that prewetting of the samples can reduce the apparent durability in short-term tests. In the termite resistance test, the three TMW species had no resistance against subterranean termites, with sample mass loss of 50% on average, compared to a 30% for the unmodified wood controls.
B Cortes, B Bond, A Taylor, J Lloyd