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Mechanical resistance of Pinus radiata CCA treated and face jointed with PVA adhesive
1999 - IRG/WP 99-40140
Due to the increased use of Pinus radiata timber composites (laminated structural members, panels, etc), its low natural durability and the toxicity of phenol-formaldehyde type adhesives, a PVA (polyvinyl acetate) adhesive was evaluated in machined and rough CCA treated and untreated face joint samples under DIN 68602 (EN 204-205) standard for groups of requirement 3 and 4. The results showed that the adhesive resisted the face joint in machined samples without CCA treatment. Rough wood samples did not meet the standard. The effect of the CCA treatment up to 4 kg oxide/m3 prior to the bonding produced a decrease in the mechanical strength of the joint in both types of roughness. Treated and machined samples had similar behaviour as rough untreated samples. The selected adhesive is not good in applications on weather exposed service of composites, since in group 3 requirement all samples failed the bending test at the adhesive joint and not at the clean wood portion.
M C Rose, L Reyes, P León

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

Properties of plywood and Oriented Strand Board manufactured with an organic insecticide incorporated in the adhesive formulation
2000 - IRG/WP 00-40174
The efficacy of Fipronil as an insecticide has been established by laboratory and field experiments and commercial use against a broad range of insect pests for various crops. It can be used by either foliar or soil application. Development is underway for the non-agricultural uses of fipronil. Research is ongoing for the control of ants, cockroaches, fleas, ticks, houseflies, mosquitoes, termites and other pests. Several countries in the world have experienced extensive termites damage. The protection of structural and non-structural cellulosic products against termites may be required in the near future. With the increase uses of wood composites in wide ranging applications, protection against termites will represent one of the criteria of material selection. Fipronil was added in the formulation of adhesive during the laboratory manufacture of plywood and oriented strand board. The average MOE and MOR from of plywood was about 1.1 to 1.2 million psi and 8000 to 9100 psi, respectively. Shear strength and wood failure varies from 191.6 to 239.9 psi and 73% to 92%, respectively. Analyses of variance showed that statistically there were no significant different of all properties tested between fipronil concentration (0 - 375 ppm) at 5% level. This study indicates that fipronil has no affect on MOE and MOR under bending regime, and on the shear strength and the wood failure. After 18 months above and ground contact exposure in Gainesville, Florida, a level of 150 to 200 ppm successfully control the termite attack.
D P Kamdem, J H Hope, A Jermannaud

Effect of alkaline phenolic resin adhesive on the stability of preservatives incorporated into the glue-line of plywood
1991 - IRG/WP 3650
Stability of preservatives was determined by gaschromatographic analysis when they were applied to glue-line treatment of plywoods. Among organophosphorous insecticides, emulsified forms of chlorpyrifos, dichlofention and diazinon were more stable than others. Fenitrothion, pyridafenthion and phoxim were not practically acceptable as emulsifieable forms due to the relatively low recovery rates after an accelerated ageing (heat exposure at 60°C after hot-press). IF-1000, an organoiodine fungicide, seemed to be less stable under the influence of heat, although the fungicide was better than the other tested organoiodine chemical (Sunplas).
S Fushiki, Y Katuzawa

Solution stability and Mechanical properties of Chitosan treated Pine
2005 - IRG/WP 05-30377
During the last years the research on chitosan as a wood preservative has been enhanced. Up to now, most of the research has been applied to the anti-fungal properties of chitosan, and no research was conducted on the solution stability of chitosan solutions in repeated trials by impregnation of wood, or on the mechanical properties of chitosan-treated wood. In this paper, the stability of high- and low-molecular weight chitosan solutions (2,4% (w/v) concentration) was investigated in 15 repeated impregnation cycles using pine (Pinus sylvestris) samples. Changes in the following parameters of the treatment solution were examined: uptake of chitosan, viscosity, pH, molecular weight and concentration. In addition, the following mechanical properties of chitosan-treated pine were determined using a paired experimental design: modulus of elasticity (MOE), static bending, impact bending strength, static hardness, shear strength, tensile strength, compression strength and adhesion of paint to wood. Overall, an average chitosan uptake by the pine samples in the order of 15 to 16 kg/m³ was obtained. In the trials for determination of solution stability, the uptake, viscosity and concentration remained unchanged. However, the pH of the solutions increased, and the average chitosan molecular weight decreased, with the high molecular weight chitosan displaying larger changes than low molecular weight chitosan. No significant changes in the mechanical properties of pine treated with high-and low molecular weight chitosan (2,4% (w/v) concentration) were determined as compared to untreated wood samples.
E Larnøy, M Eikenes, H Militz

The effect of oil-borne preservative treatments on the shear strength of FRP/wood composite adhesive bonds
2003 - IRG/WP 03-40265
Reinforcement of structural wood components with Fiber Reinforced Polymer (FRP) will enhance the beam’s strength, but actual data on long-term durability is sparse, not well documented or not readily accessible. In this study, bond properties of FRP-wood composite materials were investigated following treatment with creosote or copper naphthenate preservatives. The properties investigated included stress and the percentage of wood failure experienced in shear (ASTM 1998). When tested in a wet condition (following a vacuum/pressure soak), creosote-treatment adversely affected the wood failure values associated with specimens fabricated with a pultruded FRP composite sheet (E-glass fiber, bonded with urethane). When these tests were conducted with samples under ambient conditions, the shear strength of this material was also adversely affected by creosote. In addition, both creosote- and copper napthenate-treatment adversely affected the shear strength of a SCRIMP™ fabricated FRP material (carbon fiber, vinyl ester matrix).
B Herzog, B Goodell, R Lopez-Anido

Paintability and gluability of wood treated with arsenic-free and chromium free preservative treatments
2006 - IRG/WP 06-40342
The objective of this project was to study, in comparison with traditional CCA treatment, the paintability and gluability of wood treated with arsenic-free and chromium-free preservative treatments. Four formulations, all certified CTB P+, were selected in accordance with their representativeness of the preservative product market: one CCA reference formulation and three chromium and arsenic free formulations (S1, S2, and S3). The species of wood chosen was the Scots pine. A wettability study has shown that the four preservative treatments lead to very different surface characteristics. CCA and S1 treatments make wood hydrophobic whereas S2 and S3 make wood hydrophilic. The paintability phase was carried out on six types of coatings including waterborne and solventborne products, paints and stains. The performance of the coatings on the different treated woods was characterised by artificial and natural weathering tests. For the paints tested, the overall appearance of the test specimens after weathering was the same irrespective of the wood preservative. As regards the transparent coatings tested, the general appearance of the test specimens after weathering is generally better on CCA treated wood. However, the adhesion testing showed a tendency toward poorer adhesion for coatings on wood treated with new generation preservatives. The objective of the gluability phase was to qualify: Glue-laminated treated northern Scots pine with RPF, MUF and PU type structural adhesives, used for load bearing structures, Glue-laminated treated regional Scots pine with an EPI type non-structural adhesives, used for joinery. As such, the initial mechanical performance of the different glue bonds was evaluated through shear testing by compression. The durability of the assembly was evaluated by delamination testing. The wood treated with new generation products therefore displays satisfactory gluability with RPF, MUF and PU type structural adhesives. Results are more variable with EPI type non-structural adhesives.
L Podgorski, G Legrand

Fungal decay resistance and durability of wood products made from borax-impregnated wood and bonded with corn starch and tannin adhesive
2009 - IRG/WP 09-30494
At present, the production of wood composites mainly relies on the petrochemical-based and formaldehyde-based adhesives such as phenol formaldehyde (PF) resins and urea formaldehyde (UF) resins, which are non-renewable and therefore ultimately limited in supply. This paper concerns the decay resistance of wood products bonded with a new, environment-friendly adhesive derived from abundant and renewable cornstarch and tannin.To improve the total resistance of the composite against both Coriolus versicolor and Coniophora puteana rots fungi, borax (di-sodium tetraborate) was added in proportions of 0.5%, 1% and 2% (w/w) to the cornstarch-tannin adhesives. The results showed that increasing the concentration of borax in the adhesive decreased the mechanical properties of the composite. The best way to avoid this problem was to use wood impregnated with borax. Biodegradation studies were conduced on new composites, first without any treatment, followed by borax at 0.5 % aqueous solution treatment. The results show that wood impregnated with borax, in presence of tannin and sodium hydroxide in the adhesive improves the total resistance of the wood composite against both Coriolus versicolor and Coniophora puteana rot fungi.
A Moubarik, A Pizzi, A Allal, F Charrier, B Charrier

Fungal decay resistance and mechanical properties of plywood panels made from maritime pine (Pinus pinaster) and bonded with cornstarch-quebracho tannin-phenol formaldehyde adhesive
2010 - IRG/WP 10-40490
The aim of this work is to demonstrate the performances of cornstarch-quebracho tannin-based resins designed as adhesive in the plywood production. In this way, the cornstarch and quebracho tannin was introduced in the classic adhesive formulation in order to supply a part of phenol-formaldehyde (PF). In order to evaluate the mechanical performances of optimal cornstarch-quebracho tannin-PF, plywood panels were produced and mechanical properties were investigated. These mechanical properties included tensile strength, wood failure and 3-point bending strength. The biological performance of plywood panels against both Coriolus versicolor and Coniophora puteana rot fungi were evaluated. The performance of these panels is comparable to those of plywood panels commercial PF made. The results showed that plywood panels bonded with cornstarch-quebracho tannin-PF resins (15:5:80, w:w:w) exhibited better mechanical properties than plywood panels commercial PF made. The formaldehyde emission levels obtained from panels bonded with cornstarch-quebracho tannin-PF were lower to those obtained from panels bonded with control PF. Biodegradation studies show that the presence of quebracho tannin in the adhesive improves the total resistance of the plywood panels against both Coriolus versicolor and Coniophora puteana rot fungi.
F Charrier, A Moubarik, A Allal, A Pizzi, B Charrier

Influence addition of boron compounds to adhesives on the bonding quality and fungicidal properties of glued wood
2010 - IRG/WP 10-40497
Wood is one of the most important construction materials. However, users of wood face two issues: limited dimensions and insufficient durability. These issues have been overcome with the development of bonding and wood preservation. The preservation of glued wood is elucidated in this paper. Through the addition of boric acid to adhesives, we tried to improve the fungicidal properties of glued wood. The results of mechanical testing (shear strength and delamination) showed that the addition of boric acid to glue did not have a negative impact on the performance of the glued wood. On the contrary, some properties were even improved. Unfortunately, the addition of boric acid to impregnated wood does not improve the resistance of the glued wood to brown rot fungi.
M Humar, B Lesar, A Ugovsek, M Kariz, P Kralj, M Šernek

Biological and mechanical performances of particleboard panels made from maritime pine (Pinus pinaster) and glued with cornstarch-mimosa tannin-urea formaldehyde adhesive
2011 - IRG/WP 11-40542
The objective of this work was to demonstrate the utility of cornstarch-mimosa tannin-based resins designed for application as an adhesive in the particleboard production. Bond qualities of cornstarch-mimosa tannin- urea formaldehyde (UF) (10:4:86, weight ratios) resins and commercial UF resin were assessed by using an automatic bonding evaluation system, prior to production of particleboard panels. In order to evaluate the quality of cornstarch-mimosa tannin-UF (10:4:86, weight ratios) resins, particleboards were produced and physical and mechanical properties were investigated. These physical properties included rheological and solid phase 13C NMR analysis of resins. The biological performance of particleboard panels against both Coriolus versicolor and Coniophora puteana rots fungi were evaluated. Internal bond, surface soundness, modules of rupture and modulus of elasticity mechanical properties of particleboards bonded with cornstarch-mimosa tannin-UF (10:4:86, weight ratios) resins were also determined. The results showed that it is possible to add cornstarch and mimosa tannin respectively up to 10 % and 4 % to the UF resin without to alter the physical and mechanical properties of the boards. The performance of these panels is comparable to those of boards made using commercial UF resin. Biodegradation studies show that the presence of mimosa tannin in the adhesive improves the total resistance of the particleboards panels against both Coriolus versicolor and Coniophora puteana rot fungi.
A Moubarik, F Charrier, A Pizzi, A Allal, B Charrier

Curing kinetics of nano cupric oxide (CuO) modified PF resin as wood adhesive: Effect of surfactant
2013 - IRG/WP 13-40620
The effect of nano cupric oxide (CuO) in combination with surfactants on the curing kinetics of phenol formaldehyde (PF) resin, as well as the bonding strength of plywood prepared using the modified resin were investigated in this study using dynamic and isothermal differential scanning calorimetry (DSC). The result showed that the incorporation of nano CuO along with alkane surfactant made in the laboratory clearly reduced the apparent activation energy of the PF resin and improved the addition and condensation reactions of the PF resin. Inclusion of the surfactant had the further effect of compensating the influence of diffusion control caused by nano CuO alone. The shear strength of plywood suggested that the addition of nano CuO (1%) alone or in combination with alkane surfactant (0.55%) or sodium lignosolfonate (0.55%) in the PF resin mixture was sufficient to meet the requirement of wood-based composites manufacturing.
Wei Gao, Guanben Du

Thermal durability and biodegradation of tannin lignin adhesives
2014 - IRG/WP 14-40657
Mimosa tannins and lignosulfonates were used in wood adhesives formulation to substitute resins based on formaldehyde. Mimosa tannins were mixed with either glyoxalated sodium lignosulfonates or glyoxalated ammonium lignosulfonates. The ratios of mimosa tannins and sodium lignosulfonates varied from 20% tannins to 60% tannins. The thermal durability of the adhesives were analysed by thermogravimetric analysis (TGA), thermomechanical analysis (TMA) and differential scanning calorimetry (DSC). Mimosa tannins-sodium lignosulfonates and maritime pine bark tannins-ammonium lignosulfonates adhesives were made at the optimised tannin-lignin ratio. The thermal durability of these resins were also analysed by TGA, TMA and DSC. The results showed a thermal stability of the adhesives up to approximately 200°C. Moreover, biodegradation tests on the most effective resins were carried out, by confronting our adhesives against Coniophora puteana and Coriolus versicolor. The results showed that the adhesives were resistant to a fungal attack.
L Chupin, B Charrier, A Pizzi, F Charrier

Lignin-Based Adhesive for Engineered Wood Products
2016 - IRG/WP 16-50319
Lignin as a naturally occurring polyphenolic compound has an excellent potential to replace petroleum-based phenol in formulation of phenol-formaldehyde adhesive that are used in manufacturing of engineered wood products. However, there are three major obstacles in application of polymeric lignin as phenol replacement: 1) low reactivity toward phenol, 2) high molecular weight, and 3) high polydispersity or heterogeneity. Depending on the source (hardwood, softwood or annual crops), and isolation processes (kraft, sulphite, organosolv, steam explosion enzymatic pretreatment) lignin properties will differ. Choosing suitable lignin with potential higher reactivity toward phenol in this study helped us to formulate a 100% lignin-based phenolic adhesive that had shown excellent water resistance and mechanical properties. The lap shear strength results of analysed plywood samples (using 100% lignin-based adhesive) were similar to a commercially phenol resorcinol formaldehyde (PRF) adhesive formulated for manufacturing of plywood and ordinated strand board (OSB).
I Kalami, M Arefmanesh, E Master, M Nejad

Properties and potential use of Irvingia gabonensis and Irvingia wombolu kernel extracts as natural wood adhesives: Towards formaldehyde free wood composite products
2018 - IRG/WP 18-40832
Irvingia species are widely distributed in central and West Africa as well as parts of Asia and are earmarked for domestication due to the multitude of potential products that can be obtained from them. With renewed interest in renewable sources, the current study establishes the feasibility of utilizing extracts from Irvingia gabonensis and Irvingia wombolu kernels as wood adhesives. Proximate analysis of the kernels was carried out and chemical analysis of I. wombolu kernels revealed the following composition: carbohydrates (21.2%), protein (6.5%), fat (67.5%), ash (2.3%) and moisture (2.5%). I. gabonensis kernels had the following composition: carbohydrates (16.8%), protein (7.97%), fat (70.5), ash (2.4%) and moisture (2.3%). Three extraction methods were compared in terms of efficiency, yield and adhesive properties, i.e. water with no catalyst, as well as sodium chloride, and sodium metabisulphite. The results showed that there was no significant difference in the yields from different extraction methods and species; and therefore a simple water extraction without catalyst was adequate. The adhesives were applied on glass fibre paper strips, the tensile strength of the paper strips was evaluated. The results showed that adhesives produced using water extraction process had the highest tensile strength and elastic modulus for both species, with values of 14700 and 13600 N/m-g; and 46.7 and 44.1 GPa respectively. A comparison of strength properties was made with a commercial formaldehyde-based adhesive, Bondtite®. The results revealed that the tensile strength of Bondtite® is about 17.6% higher than the highest strength of the Irvingia adhesive. The study concluded that Irvingia adhesive is a promising non-formaldehyde adhesive that can be used in wood composite applications.
A O Alawode, S O Amiandamhen, M Meincken, L Tyhoda