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Physical and biological properties of albizzia waferboards modified with cross-linking agents
1995 - IRG/WP 95-40043
Chemically-modified low-density waferboards with cross-linking agents were produced using a fast-growing species of hardwood albizzia (Paraserienthes falcata Becker) as a raw materials and isocyanate resin as a glue adhesive. For the chemical modification, the vapor-phase formalization of the boards and the pad-dry-cure treatment of wafers with cross-linking agents were employed. The vapor-phase formalization was conducted for 5, 10 and 24 hours using tetraoxane as a source of formaldehyde, and the pad-dry-cure treatments with glutaraldehyde and ethyleneurea compound (DMDHEU) were made after impregnation of their 5 and 10% aqueous solutions of each chemical. Sulfur dioxide was used as a catalyst in both treatments. About 70% of antiswelling efficiency (ASE) was gained in all treated boards irrespective of reaction time or solution concentration. All treated boards were very stable to water soaking even in the 2-hour boiling on thickness swelling as well as linear expansion. Laboratory tests with brown-rot and white-rot fungi revealed that decay was completely suppressed in formaldehyde-treated boards, and small losses in weight were counted in other treated boards. All treated boards were also effective in resisting to the attack by the destructive termite Coptotermes formosanus.
S Yusuf, Y Imamura, M Takahashi, K Minato

Oxygen index levels and thermal analysis of wood treated with melamine-formaldehyde-boron combinations
1997 - IRG/WP 97-30135
Melamine formaldehyde (MF) resin was impregnated into scots pine (Pinus sylvestris L.) specimens with aqueous solutions of 5, 10 and 20% concs. Boric acid (BA) and borax (BX) was added to MF resin at the concentration levels of 0.25, 1.00 and 4.70% to each level of resin concs. BA and BX mixture was prepared at the 5:1 (w/w) ratio considering resultant pH of solutions and better fire resistance. Untreated and treated wood with all combinations were subjected to oxygen index test according to ASTM D 2863-91 and thermal analysis. Results were evaluated in terms of improvement of fire retarding performances of wood by sole or combination treatments.
M K Yalinkilic, W-Y Su, Z Demirci, E Baysal, M Takahashi, S Ishihara

Combined effects of the treatment of wood with formaldehyde
1978 - IRG/WP 3117
Treatment of fibrous materials with reagents in a vapor phase is neither new nor unique. Numerous examples exist in literature of vapor phase experiments on cellulose fibers and fabrics, and on wood. For many years the textile research and industry have used vapor phase processes for the treatment of textiles. The chemical modification of cellulose is based on different types of reactions e.g. esterification, alkylation, resin formation or polymerization, monomer grafting and crosslinking. Vapor phase treatment of wood offers certain potential advantages over the conventional liquid phase wood impregnation. The higher mobility of low molecular weight compounds in the gaseous state ensures a rapid, uniform and homogeneous distribution throughout the wood structure. The vapor phase treatment of wood is also a better approach from the standpoint of cell wall penetration. Bulking, which takes place in the cell wall only, means that less chemicals are required and that the final weight of the composite is limited. Furthermore, due to the low viscosity of a gas, the application of a lower pressure differential remains possible. Within the framework of a wood improvement programme carried out at the Laboratory of Wood Biology and Wood Technology (University of Ghent, Belgium) the treatments were based on the impregnation of wood with liquid synthetic monomers and with gaseous formaldehyde. The results of the hygroscopic and dimensional behaviour of the wood-plastic-combinations have been published previously. Other papers deal with the physical and chemical interactions between the synthetic products and the natural polymers of the cell wall. This contribution will be restricted to the treatment of wood with formaldehyde in the gaseous state.
M Stevens, J Schalck

Thermotolerant mould growth in dehumidifier kilns in New Zealand
1996 - IRG/WP 96-10169
Growth of Aspergillus fumigatus and Paecilomyces variottii is common on wood dried in dehumidifier kilns that operate within a temperature range of 35-55°C. Aspergillus fumigatus causes an unacceptable blue / grey discolouration of the woods surface and prolonged exposure to spores during handling of mouldy wood can cause health problems amongst timber workers. A survey of dehumidifier kiln operators in New Zealand was carried out to ascertain the extent of the problem and investigate control options. Significant growth only occurred if initial wood moisture content was above 80%. Results suggested that this was because high relative humidity (98-100%), for periods in excess of 5 days, was a requirement for extensive and profuse growth to occur. Only 3 of the 26 antisapstain treatments tested using a 3 week laboratory trial gave control of Aspergillus fumigatus at 40°C. Fumigation with 4 ppm (mg/litre of air) of formaldehyde gas controlled growth of Aspergillus fumigatus for periods up to 5 days and a second fumigation was often needed for long drying cycles (> 12 days). It seems likely that growth of thermotolerant moulds became a problem when use of pentachlorophenate as an antisapstain treatment was phased out (1988-89). Laboratory trials showed that this was one of the few fungicides that controlled Aspergillus fumigatus.
R N Wakeling, J G Van der Waals

Effects of a formaldehyde and sulphur dioxide treatment on decay and mechanical properties of aspen waferboard
1983 - IRG/WP 3242
Aspen wafers were sequentially treated under vacuum with formaldehyde and sulfur dioxide gas and pressed into waferboard bonded with powdered phenol formaldehyde resin. Decay resistance and strength properties were determined before and after simulated weathering. The water resistance of the phenol bonding system was lost in board made from the gas-treated wafers. This white rot fungus Coriolus versicolor was unable to decay treated waferboard in a soil block test, but the brown rot fungi Gloeophyllum trabeum and Poria placenta decayed the samples as severely as untreated controls.
E L Schmidt

Durability of surface preserved wood particle boards submitted to atmospherical influence
1995 - IRG/WP 95-40039
The worldwide problem of the continuously growing deficit of high quality natural wood material has caused the attempts of many research workers to find effective composites such as wood particle boards (WPBs) for replacing the massive wood for constructive purposes, depending on where the boards are exploited - in the open or under a shed, they are submitted to various climatic factors such as heating, drying, moistening, frosting, irradiation, that's why for reaching high atmospheric resistance, it is very important, a durable protection of the WPBs with suitable coatings against the atmospheric influence to be ensured.
L Valcheva

Treatment of wood with formaldehyde. Acid catalysis of the reaction between formaldehyde and wood
1980 - IRG/WP 3146
Formaldehyde reacts with the free OH-groups in wood forming cross-linking bonds. The reaction can be brought about without any catalyst but in that case the activation energy is very high and high temperatures and long reaction times are needed. Normally, the reaction is catalysed by different acids. Acid catalysts, however, tend to degrade the cellulose and the wood matrix causing reduction in the strength of the wood. The effect of the specific properties of catalysts on the cross-linking and hydrolytic reactions as well as the reaction kinetics have been inadequately investigated. Investigations on the treatment of wood with formaldehyde were started in 1976 at the Forest Products Laboratory of the Technical Research Centre of Finland. In the beginning, HCl-catalysed treatments were used which proved to reduce the strength properties of wood rather strongly. In continued trials more satisfactory catalysts have been sought in order to achieve maximal formaldehyde cross-linking and minimal degradation of the wood. The tests have included various inorganic and organic acids and metal halides soluble in water as well as sulphur dioxide (SO2) and boron trifluoride (BF3) in vapour phase. Some of the results are reviewed in this paper.
T Vihavainen, K Piispanen, P Mansikkamäki

Microscopical analysis of formaldehyde-acid modified wood
1981 - IRG/WP 3182
Cross-linking of wood with gaseous formaldehyde improves its hygroscopic and dimensional behaviour, and its resistance against micro-organisms. However, formaldehyde cross-linking reactions take place only in the presence of an acid catalyst, which results in losses in mechanical By optimization of a formaldehyde-sulfur dioxide vapour phase process the reaction conditions were established to limit losses in modulus of elasticity and bending strength to a few percent. Under these circumstances, impact strength losses of about 50 to 75% were still noted. The reaction of formaldehyde with cellulose has been studied intensively in textile research. However little is known on the fundamental aspects of the interaction of formaldehyde with lignin and wood. In order to get further insight into the effects of a formaldehyde-acid catalyzed reaction on the technological properties of wood a fundamental analysis of the interactions of both compounds with wood has been carried out.
M Stevens, N Parameswaran

Improving the weather resistance of glue-laminated jarrah and karri
1994 - IRG/WP 94-40017
Surface modification and dimensional stabilisation significantly increased the dry and wet shear strength of karri and jarrah lap-shear specimens (laminates) bonded with resorcinol formaldehyde. The combination of surface modification (sanding/sodium hydroxide treatment), and furfurylation produced the highest dry and wet shear strengths. Acetylated laminates had the lowest dry bond strength, but the lowest loss of strength on wetting. In most cases karri laminates showed higher dry, but lower wet shear strength than jarrah. Untreated laminates rapidly delaminated during artificial accelerated weathering, but surface modification and dimensional stabilisation significantly increased the resistance of specimens to delamination. Only a small proportion (5-10%) of acetylated specimens delaminated during accelerated weathering and surface modified acetylated laminates showed no delamination during the weathering test. Laminates treated with a combination of surface modification and furfurylation showed less delamination than specimens treated by surface modification alone. Treatments that increase both glue bond strength and dimensional stability appear to offer an effective means of improving the weathering resistance of glue-laminated karri and jarrah.
J Balfas, P D Evans

Curing conditions for a low formaldehyde etherificated melamine resin
1998 - IRG/WP 98-40108
Waterbased methanol etherificated melamine formaldehyde resins have the potential to increase the resistance of impregnated wood against wood destroying fungi. Previous studies indicated that the resin with the lowest formaldehyde content tested showed the best results regarding fungal resistance, dimensional stability and formaldehyde emissions after curing. In the present paper the influence of curing-time and curing-temperature of the resin with the lowest formaldehyde content is presented. It is demonstrated, that a sufficient curing of the resin requires temperatures in the range between 120-140°C for a period of several hours. The addition of pure urea leads to reduced formaldehyde emissions while the anti-fungal effect of the resins increases or remains the same.
D Lukowsky, R-D Peek, A O Rapp

Biological resistance of wood treated with waterbased resins and drying oils in a mini-block test
1998 - IRG/WP 98-40107
In recent years it was found that the resistance of wood against fungal degradation could be increased by impregnation with an etherificated melamine formaldehyde resin. Using this resin as a reference, a waterbased fatty acid modificated alkyd-resin and two drying-oils were assessed for their biological performance in a mini-block laboratory test. Although drying-oils, like linseed-oil, are often used as a binder in paints, little information is available about the resistance of wood impregnated with these oils against wood destroying basidiomycetes. The fungi used in this test were the brown rot fungi Coniophora puteana, Gloeophyllum trabeum and the white rot fungus Trametes versicolor. The results showed considerable less mass loss of the melamine resin and the drying oils treated wood compared to the untreated Scots pine (Pinus sylvestris) controls. The mass loss of the oil treated specimens, however, was obviously depending on the fungus and the applied treatment and the wood species.
M Sailer, A O Rapp, R-D Peek

Evaluation of the biocide diffusion from treated wood in indoor air. Bibliographic study
1990 - IRG/WP 3584
Within the frame of the risk assessment of the wood preservation products for the Health, the treated wood risk particularly when it is installed in dwellings becomes most important. The European directive "Building materials" (89/106/CEE) mentions the basic requirements with the buildings must comply. Annexe l states in particular that "the building must be conceived and built in order not to become a threat to the Hygiene or the health of the inhabitants. Thus, the treated wood installed in dwellings is concerned. Due to the lack of the official standardized methods, it has appeared interesting to study through literature: -- the well-known methods concerning Formaldehyde diffusion from glue of particle boards, -- the existing works on biocides diffusion from treated wood, -- the parameter entering in the evaluation of quantities diffused in the air, -- the assessment of actual results. This study concludes that the evaluation of biocides diffusion in the indoor air is made by the following process: -- a definition of the experimental protocols adapted for the claims, -- an estimation of the concentrations in the indoor air, from the experimental results, -- an assessment of the human health risk. Some of the existing works already give a better understanding of the factors and parameters which must be taken account. They will make easier the approach of the various experts who will have to cooperate to set up the standard.
A Pichard

In situ testing the influence of melamine resins on the enzymatic activity of basidiomycetes
1999 - IRG/WP 99-30194
Waterbased methanol etherificated melamine formaldehyde resins have the potential to increase the resistance of impregnated wood against wood destroying fungi. The mechanism of the increased wood durability is not clear yet. In the present paper the possible interference of melamine resins with wood degrading enzymes of Coniophora puteana and Trametes versicolor was investigated as a possible contribution to the increased wood durability. An in situ photometric assay was used to measure the enzymatic activity against Walseth cellulose, pine sapwood as well as lignin and xylan preparations.
D Lukowsky, F Büschelberger, O Schmidt

Dimensational stabilisation of wood
1981 - IRG/WP 3171
A review is given of the studies on the dimensional stabilisation of wood which have been carried out in the laboratory 5.14 "Wood Technology" since 1967. All stabilisation methods known have first been compiled from the available literature. Practical studies were then started. Wood was treated with monomers (styrene, methyl metacrylate, isocyanate), formaldehyde, tannin and sugar. Despite a satisfactory reduction of the shrinkage behaviour, the costs of these methods are prohibitive. A recently developed heat treatment adjusting wood moisture content, temperature and pressure is more economical. This method is suitable for all timber species.
A Burmester

Selecting fumigants for treatment of internal decay in wood
1986 - IRG/WP 3370
A number of potential fumigants were screened with respect to their toxicity to decay fungi, (Poria carbonica, and Lentinus lepideus) and their sorption characteristics on Douglas Fir (Pseudotsuga menziesii Mirb. Franco) wood. Wafers of infected wood were exposed to different fumigant concentrations for various times then cultured to determine viability. The lethal concentration X time (ct) factors were determined for each fungus species and fumigant chemical. The "pulse chromatograph technique" was used to determine sorption isotherms for the fumigants to establish the relative degree of interaction between the chemicals and wood. Formaldehyde, chloropicrin (trichloronitromethane), and methylisothiocyanate (MIT) were the most fungitoxic of the chemicals investigated. MIT had the strongest affinity for wood, suggesting that this fumigant should persist longer in treated wood than chloropicrin. The proportion of vapor adsorbed on wood increased greatly with decreasing temperature and was generally higher in decayed wood than in sound wood and in 8% moisture content wood than in dry wood.
P A Cooper

Stability of bifenthrin in a commercial phenol-formaldehyde plywood glue
2003 - IRG/WP 03-30311
Liquid phenol formaldehyde (PF) glue mixes used for plywood manufacture are strongly alkaline. At this pH insecticidal additives may not be stable for long periods. In order to establish practical working life of the synthetic pyrethroid insecticide, bifenthrin, in liquid PF glues the concentration of bifenthrin in the glue mix was measured under laboratory conditions over a 24 hour period. Glue batches were prepared in a laboratory mixer set up on an electronic balance with two dose rates of bifenthrin. The glue was stirred continuously, with a cover in place to reduce evaporation. Four replicate portions of glue were removed from the mixer and applied to fluoropolymer-coated rubber discs at fixed periods. The discs were cured immediately in an oven, during which time the film set and became detached from the surface. These discs were extracted with toluene-formic acid (90:10) mixture and the extracts analysed using capillary column GC with electron capture detection. Bifenthrin was found to be exceptionally stable in alkaline PF glue. When the glue was mixed under conditions preventing premature polymerisation, no measurable bifenthrin degradation occurred during the 24 hours.
M J Kennedy, P A Collins, R D Vella

Leaching performance, decay and termite resistance of wood treated with boron compounds incorporated with phenol-formaldehyde resin
2009 - IRG/WP 09-30503
A resol-type phenol-formaldehyde (PF) resin was synthesized and designed to penetrate wood incorporated with boron compounds in order to immobilize boron in wood. The leaching performance, decay and termite resistance of treated wood was investigated. Three kinds of boron compounds, that is, boric acid (BA), borax (BX) and disodium octaborate tetrahydrate (DOT), were selected to mix with PF and two species of wood (Chinese fir and Masson pine) were selected as the treating samples. The leaching process of boron from wood blocks was performed according to the American Wood Preservation Association (AWPA) standard E11-06. And the boron content in treated wood and leachates were determined by inductively coupled plasma optical emission spectrometer (ICP-OES). The results showed that boron leaching was reduced markedly and negligible boron was leached in some treatments. In laboratory termite tests against Coptotermes formosanus Shiraki, treated wood showed low weight loss. In addition, in laboratory decay test using a brown-rot fungus (Gloeophyllum trabeum) revealed that the decay resistance of PF-boron treated wood was also greatly improved.
Liping Yu, Jinzhen Cao

Properties of strand board bonded with ammonium pentaborate (APB) modified phenol formaldehyde resin
2009 - IRG/WP 09-40455
Ammonium pentaborate (APB) is combined with phenol formaldehyde (PF) resin in this study to develop a high-performance wood-based composite. The effect of APB and its combination with polyethylene glycol (PEG) on the physical, mechanical properties as well as formaldehyde emission of strand board were tested and compared with disodium octaborate tetrahydrateand (DOT) and zinc borate (ZB). The results showed that APB has negative effect on the mechanical properties of the strand board, but the distribution of APB only on the surface in the 3-layer strand board can reduce this negative effect significantly. Except only marginal increase on the thickness swelling, PEG displays a positive effect on internal bond strength, modulus of rupture (MOR), and modulus of elasticity (MOE). As expected, APB showed decreasing effect on the formaldehyde emission.
Wei Gao, Jinzhen Cao

The Effects of Some Fire Retardant Chemicals on the Decay Resistance of Medium Density Fiberboard (MDF)
2010 - IRG/WP 10-30536
The objective of this study was to determine the decay resistance of Medium Density Fiberboard (MDF) treated with 5% and 10% concentration of various fire retardant (FR) chemicals. Experimental panels were produced using by melamine-urea-formaldehyde (MUF) resins having 10%, 15% and 20% of melamine content. MDF specimens were subjected to decay resistance test performed according to modified EN 113 standard method using white-rot fungus, Trametes versicolor. It was found that the weight loss (%) of MDF specimens treated with chemicals were lower than those of control panels. Especially, the best results were obtained from MDF specimens treated with zinc borate (ZB). Furthermore, decay resistance of the MDF specimens improved with increasing melamine content in the MUF resin and increasing chemical concentration.
D Ustaömer, M Usta, Ü C Yildiz, S Yildiz, E D Tomak

Effect of 4 Preservatives on Physical, Mechanical and Mold-Resistant Properties of Bamboo Oriented Strand Boards
2010 - IRG/WP 10-40483
This study investigated the effects of 4 preservative systems on physical, mechanical and mold-resistant properties of bamboo oriented strand board (OSB) panels bonded with urea formaldehyde resin. Preservative A (Zinc Borate), B (IPBC), C (AAC+Borate) and D (carbendazim + prochloraz) were incorporated with strands during blending at three loading levels. The results showed that the mechanical and physical properties of bamboo OSB experimental panels met the requirements for OSB/2 specified in the China Industrial Standard LY/T 1580-2000, with the exception of 24-hour water soaking thickness swelling properties of panels containing preservative C. The panels containing preservative A had the most excellent physical and mechanical properties while those containing preservative C presented the lowest quality, which indicated that addition of preservative C did have detrimental effects on the quality of panels. Of the 4 preservative systems, preservative B(IPBC) was proven to be the most promising as it fully inhibited the mycelia growth of the 3 experimental molds at the loading level of 0.5% and still provided the OSB panels with satisfactory physical and mechanical properties. Preservative A (Zinc Borate) and Preservative C (AAC+Borate) were tested to be only effective against the growth of Trichoderma lignorum at their corresponding highest loading levels, while preservative D showed no protection against the molds within the limit of this study.
Juwan Jin, Daochun Qin, Wanshu Wei, Kuan Fan

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

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

Multilayer hot-press drying and chemical modifying of poplar wood with urea-formaldehyde prepolymer
2011 - IRG/WP 10-40539
The objective of this study was to determine the technology of chemical modifying and multilayer hot-press drying on poplar wood. The chemicals were impregnated into cell lumen space by pulse-dipping machine to improve the dimension stability and mechanical property of timber. The timbers were compressed and dried by the multilayer hot-press drying to increase the density of timber. Results indicate that the physical and mechanical properties were compared between modified timber and natural timber. Based on the findings, the results demonstrated that the density of modified wood improves by 58.1 %, the hardness of the end profile surface improves by 66.6 %, while tangential direction 210 % and radial 160 %, the bending strength improves by 77.8 %, the bend elastic modulus improves by 66.3 %. The improvements of mechanical property were owed to the reinforcement of chemical on the cell wall and lumen space of wood. Characteristics of Fourier Transform Infrared Spectroscopy (FTIR) and X-ray diffraction (XRD) for modifying were studied using FTIR spectrometer and XRD instrument. The intensity of hydroxyl absorption peak in the infrared absorption spectrogram decreased significantly, and that of carbonyl decreased lightly. The C=O absorbance at 1750 cm-1 reduced as result of the deacetylation of hemicelluloses and reaction between C=O and -NHCH2OH of urea-formaldehyde prepolymer.. The crystallinity of wood decreased lightly from 39.65 % to 37.06 %. Fourmorphologic models of chemical within wood were discovered by SEM.
Guofeng Wu, Yifei Jiang, Sheng Yao, Junwen

Effect of P/F ratio, PF concentration and treating method on boron leaching from wood treated with PF modified boron compounds
2011 - IRG/WP 11-30559
In order to immobilize boron in wood, three kinds of resol-type phenol-formaldehyde (PF) resin with different P/F ratios were synthesized in laboratory and incorporated with three types of boron compounds to treat wood. The used boron compounds included boric acid (BA), borax (BX) and disodium octaborate tetrahydrate (DOT). The leaching test of boron from wood blocks was performed according to the American Wood Preservation Association (AWPA) standard E11-06. The boron content in treated wood blocks and leachates were determined by inductively coupled plasma optical emission spectrometer (ICP-OES). The results of experiment indicated that higher PF concentration is preferable for better boron fixation. There was no significant difference between the three boron compounds used in this experiment with only slightly higher boron leaching for borax. The “Two-step method” showed lower boron leaching than “One-step method”, which may be due to the lower boron retention before leaching caused by the boron leaching during PF impregnation process. Considering the P/F ratio, PFB (P/F ratio: 2.0) and PFC (P/F ratio: 2.2) showed a little lower boron leaching than PFA (P/F ratio: 1.6).
Liping Yu, Jinzhen Cao

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

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