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Thermally modified timber (TMT) for decking applications – determination of relevant surface properties
2011 - IRG/WP 11-40544
In recent years thermally modified timber (TMT) entered various market segments. It is used for facades, horticultural equipment, garden furniture, and also for kitchen and bathroom cabinets. However, flooring turned out to be the most important application for TMT, either as interior parquet or as exterior decking. Besides durability and dimensional stability, which had been the initial target properties of TMT, research activities need to focus also on flooring relevant properties. The performance of flooring is mainly characterized by its optical appearance, thermal behaviour and different mechanical properties, e. g. hardness and bending strength. Consequently, in the frame of a worldwide inter-laboratory test on quality measures for TMT, which was initiated in the frame of IRG in 2008, studies on the sensitivity of TMT on typical flooring loads were considered. Within this study color and heat flux density measurements were conducted to determine the suitability of TMT in terms of thermal comfort. The heat flux density was barely affected by the heat treatment, because it is mainly determined by the material density. Thermal modification did not lead to a remarkable loss, neither in density nor in heat flux. However, timber turned out to be preferential compared to mineral or polymer-based flooring materials suffering from less thermal comfort. The most important mechanical load for flooring was regarded in static and dynamic hardness tests. As TMT is known to be especially susceptible to dynamic loads, a method for determination of dynamic hardness was developed and applied to differently severe treated TMT. The development based on the Brinell hardness principle and aimed on examining differences between static and dynamic loads on hardness as well as on the possibility to convert both hardness values into each other. Extensive hardness tests with 24 different native wood species and TMT were conducted. The dynamic hardness decreased with increasing treatment intensity (in maximum by 20 %), whereby the axial hardness was significantly less affected compared to radial hardness. Furthermore, the reduction in hardness was found to be reliably predictable by color measurements.
L Meyer, C Brischke, C R Welzbacher

Performance results of wood treated with CCA-PEG
1986 - IRG/WP 3363
The addition of polyethylene glycol (PEG) to the CCA system has been shown to reduce the surface hardness of poles and ease spur penetration during climbing. This paper addresses the results of tests dealing with preservative retention and penetration, permanence of CCA and PEG, strength, drying rate, and checking characteristics.
W P Trumble, E E Messina

The effect of service life and preservative treatment on the hardness of wooden poles
1989 - IRG/WP 3537
The surface hardness of utility poles is an important parameter which effects the acceptability of the pole as being safe to climb during line maintenance. The current investigation was designed to evaluate how the surface hardness of preservative treated utility poles is effected by the type of preservative, and the age of the poles. Chromated-copper-arsenate (CCA) treated red pine and jack pine poles which had been in place for up to forty years were located in Bell Canada's system in Ontario, and screened for use in the project. A survey of poles in three locations was made, and data collected on surface hardness using a 6-Joule Pilodyn. Other information recorded included the wood species identified by the brand, and the moisture content (using a resistance type moisture meter). Core samples were removed from each pole for subsequent measurement of preservative retention. The CCA retentions were determined using an X-ray analysis.
E B Jonsson, E M A Nilsson, J N R Ruddick

Effects of the addition of polyethylene glycol to the CCA-C preservative treatment
1985 - IRG/WP 3337
A modification of the CCA-C wood preservative system for utility poles has been investigated to see if spur penetration into the poles is assisted during climbing. Addition of polyethylene glycol to the CCA system has been shown to accomplish this purpose. This paper addresses the effects of the addition of polyethylene glycol to other physical properties germane to utility poles.
W P Trumble, E E Messina

Laboratory tests on artificial weathering of Quercus rubra crossties
1986 - IRG/WP 2252
Clear red oak (Quercus rubra) blocks were used to evaluate various types of accelerated aging tests including boil, steaming, and cyclic weathering. It was found that the repeated vacuum and pressure treatment of wood in water, steaming, oven-dry, and freezing appeared to be most effective in reducing the MOE in compression and hardness modules of wood specimens. Red oak crossties which were pressure treated with creosote - coal tar preservative were tested using the cyclic aging technique. This method will be used to establish correlation between short-term accelerated aging test results and long-term in service performance of wood crossties.
P Chow, A J Reinschmidt, E J Barenberg, S L Lewis

Soft rot decay in acetylated wood. Chemical and anatomical changes in decayed wood
2002 - IRG/WP 02-40231
Acetylated Beech (Fagus sylvatica) and Scots Pine (Pinus sylvestris) wood were studied in soil beds under laboratory conditions for longer periods. High mass losses and dynamic MOE losses were measured in non-acetylated wood and at lower weight percent gains (WPG). Rapid losses of lignin, holocellulose and ?-cellulose occurred in non-acetylated beech wood and no losses were detected at the highest WPG. Changes in chemical composition of acetylated beech wood at lower WPGs was measured. Slight changes in chemical composition of non-acetylated Scots pine wood were also observed and minor changes in acetylated wood at all WPGs; except in holocellulose. An intensive anatomical study was performed by light microscopy and SEM microscopy. The results are presented and discussed. Results showed a significant prevention of acetylation against fungal growth above 8 % and 10 % WPGs in beech and pine respectively.
B Mohebby, H Militz

Some Experiences with Stake Tests at BAM Test Fields and in the BAM Fungus Cellar Part 2: Comparison of Static and Dynamic Moduli of Elasticity (MOE)
2005 - IRG/WP 05-20320
In routine in-ground stake tests of wood preservatives at the BAM test field Horstwalde and in the BAM fungus cellar periodical determinations of both static moduli of elasticity (MOE) on the basis of bending tests and dynamic MOE on the basis of the vibration method were performed as a possible method for the assessment of fungal attack. As expected from other publications, the absolute values of the dynamic MOE were higher than those of the static MOE. With the equation used for the calculation of the dynamic MOE, the differences were greater with larger specimen sizes. Sufficient correlation was observed, regarding the course of both MOE types within the test period. For both types of MOE, wood moisture contents of the stakes above the fibre saturation point were a prerequisite for the comparability of results in succeeding determinations.
M Grinda, S Göller

A dynamic approach to assess the modulus of elasticity in wood decay testing
1998 - IRG/WP 98-20139
In this study, the changes in elastic behaviour and mass losses of different hardwood and softwood species exposed to decay in a laboratory soil tests were assessed. Wood decay was monitored using different assessment methods, namely: mass loss and changes in elastic behaviours (MOE) determination. Elastic changes were determined by static and dynamic methods, for the latter, acoustic technique was applied. The results obtained show a high correlation between dynamic and conventional static bending measurements of test specimens at different stages of wood decay. The non-destructive assessment of modulus of elasticity assessment proved to be a good tool in the prediction of early stages of wood decay.
L Machek, H Militz, R Sierra-Alvarez

Application of non-destructive techniques (durometric and ultrasonic) to evaluate the degradation of woods in service by Gloeophyllum trabeum
2001 - IRG/WP 01-20220
In order to establish the degree of degradation of wood used in construction, it is necessary to employ non-destructive methods (ultrasonic, durometric, densitometric). In this study, ultrasonic and Pilodyn durometric techniques have been applied to try to establish parameters of relationship between the values obtained by both, for their immediate application to wood in service. As a method of reference, the traditional gravimetric technique of percentage of weight loss was used. Two species of pine (P. pinaster and P. contorta), widely used as construction wood in Spain, were assayed. They were subjected to an attack of Gloeophyllum trabeum, a brown rot fungus. Data were collected at 0, 2, 4, and 6 months of incubation. While the ultrasonic technique allowed us to evaluate the degree of alteration, the determination of the hardness of the wood by Pilodyn durometry proved to be excessively aggressive applied to woods that were highly degraded, although it could be used in incipient processes of rot.
M T De Troya, L Palaia, A Navarrete, V Galvañ, R Molina, A Guijarro, J Camacho

Effect of aqueous polymer treatments on wood properties. Part 2: Mechanical properties
1990 - IRG/WP 3611
Partially air-dried sapwood of sweetgum (Liquidambar styraciflua) and southern pine (Pinus spp.) was treated with either aqueous polyacrylate or aqueous dimethyloldihydroxyethyleneurea (DMDHEU) solutions. Tests for static bending, toughness, and hardness were conducted on matched treated and untreated pieces according to ASTM Standards. Properties of pine were not affected by treatment with the polyacrylate. With sweetgum, the modulus of rupture and modulus of elasticity were reduced, while hardness was improved. For the DMDHEU treatment, reduction in property values for both species was related to curing temperature.
Z Ashaari, H M Barnes, D E Lyon, R C Vasishth, D D Nicholas

Moisture correction for ultrasonic MOE measurements above fibre saturation point in Scots pine sapwood
2006 - IRG/WP 06-20333
There is a high correlation between methods for dynamic modulus of elasticity (MOEdyn) and static modulus of elasticity (MOEstat). MOEdyn methods have been found sensitive to detect early stages of decay and may be seen as an option for non-destructive wood durability testing. As the MOEstat measurements do not change after reaching the fibre saturation point, the uncorrected MOEdyn data from ultrasonic pulse excitation method provides increasing values after fibre saturation. This is due to the effect of free water in the cell lumen on ultrasonic waves. The aim of this study was to make a moisture calibration for the MOEdyn ultrasonic pulse excitation method using Scots pine (Pinus sylvestris L.) sapwood samples. MOE was measured at five different moisture levels. Three different MOE test methods were used: MOEdyn using ultrasound and vibration excitation and the traditional MOEstat. Sound Scots pine sapwood samples treated with two copper-containing wood preservatives and two chitosan solutions were evaluated, using untreated sapwood samples as control. In this study a correction value ("k") was calculated based on data from different moisture levels for water saturated samples using four different wood treatments and control. By measuring MOEdyn ultrasonic at wood moisture contents just below fibre saturation point, a minor effect of incipient water accumulation in the wood matrix was detected. Wood treatments influence the "k" value, and a "k" value needs to be calculated for all wood treatments when measuring MOEdyn ultrasound above fibre saturation. All the three MOE test methods in this study are applicable for all wood moisture levels as long as a "k" value is calculated for MOEdyn ultrasound above fibre saturation.
E Larnøy, G Alfredsen, H Militz

High-energy multiple impact (HEMI)-test – Part 2: A mechanical test for the detection of fungal decay
2006 - IRG/WP 06-20339
The suitability of the high-energy multiple impact (HEMI)-test for detection of early fungal decay was examined. The HEMI – test characterizes the treatment quality of thermally modified wood by stressing the treated material by thousands of impacts of pounding steel balls. This method differentiates between heat treatment intensities, which are expressed by structural changes of the wood. Similar changes of the wood structure are known for wood decayed by fungi. Pine (Pinus sylvestris L.) decayed by brown rot and beech (Fagus sylvatica L.) decayed by white rot were tested. Mass loss caused by fungal decay and the resistance to impact milling (RIM) determined in HEMI-tests were found to be highly correlated. Testing of non-degraded pine, beech, and ash (Fraxinus excelsior L.) showed only marginal effects of wood density on RIM. Furthermore, annual ring angles and RIM of spruce (Picea abies Karst.) were found to be not correlated. Accordingly, the detection of strength reduction of decayed wood is not masked by variations in density and orientation of the annual rings. Previous results showed no adverse effects of weathering on RIM. Thus, the detection of fungal decay with HEMI-tests is feasible, not only for laboratory purposes, but also for wood in outdoor applications, which was already weathered.
C R Welzbacher, C Brischke, A O Rapp

High-energy multiple impact (HEMI)-test – Part 1: A new tool for quality control of thermally modified timber
2006 - IRG/WP 06-20346
Thermal modification processes improve durability and dimensional stability of wood, but the strength properties, especially the dynamic ones, are compromised and need to be considered with respect to industrial quality control. Results from standard dynamic strength testing, such as impact bending tests, suffer from high variability, and therefore require a high number of replicates. To overcome this, a new test method named high-energy multiple impact (HEMI) was developed. In the present paper heat treated beech (Fagus sylvatica L.), spruce (Picea abies Karst.), silver fir (Abies alba Mill.), and larch (Larix decidua Mill.) were investigated. The HEMI method is based on crushing small specimens by thousands of impacts of pounding steel balls in a heavy vibratory mill. The level of destruction was determined by slit sieving and analysing the size distribution of the fragments. We calculated the resistance to impact milling (RIM) based on the mass of the size fractions. RIM showed a linear correlation with the decrease in mass of the wood by the thermal treatment. The HEMI-test method has the following advantages: small number of specimens, short time for specimen preparation, small variances, high reproducibility of the results, and applicability to timber out of service for a subsequent quality control.
C Brischke, A O Rapp, C R Welzbacher

Treatment of Selected Lesser Used Timber Species against Subterranean Termites using Heartwood Extracts from Teak (Tectona grandis) and Dahoma (Piptadeniastrum africanum)
2007 - IRG/WP 07-30434
Lesser used timber species represent a valuable material for all-purpose uses but the problem is that most of them are not durable. They have, for this reason, been treated with all manner of chemicals to enhance their natural durability, especially in the tropics. Often, most of these chemicals pose a threat to the environment. Currently, one probable measure of avoiding such a threat to the environment and organisms is to treat non-durable timbers with extracts from other durable species. Some Ghanaian lesser used timber species were impregnated with heartwood extracts of Teak (Tectona grandis) and Dahoma (Piptadeniastrum africanum) and exposed in the field to subterranean termites for 4 months. The effect of these extracts in enhancing the durability of these timbers was studied in accordance with EN 252. Some of the parameters considered were visual characteristics, hardness and weight loss after exposure. The results showed some species to be significantly different in durability between control samples and their treated counterparts (after 4 months) and not in others (after 4 months). Moreover, among the species, durability was high in Pertersianthus macrocarpus while the others followed in the following order: Albizia ferruginea = Blighia sapida = Sterculia rhinopetala > Amphimas pterocarpoides > Sterculia oblonga = Cola gigantean = Antiaris Toxicaria > Canarium schweinfurthii.
A Asamoah, C Antwi-Boasiako

Treatment of Selected Lesser Used Timber Species against Subterranean Termites using Heartwood Extracts from Teak (Tectona grandis) and Dahoma (Piptadeniastrum africanum)
2008 - IRG/WP 08-30476
Lesser used timber species represent a valuable material for all-purpose uses. However, most of them are not durable. They are, for effective utilization, often treated with all manner of toxic synthetic substances to enhance their natural durability, especially in the tropics where conditions favour their deterioration. Most of these toxic synthetic substances often pose a threat to the environment. Currently, one probable measure is to treat low durability timbers with extracts from highly durable ones. Heartwood water extracts of Teak (Tectona grandis) and Dahoma (Piptadeniastrum africanum) were impregnated into ten Ghanaian LUTS and exposed in the field to the ground for 8 months in accordance with European Norm 252. Visual durability ratings, hardness and mass losses were measured in assessing their field performance. Teak extract did less harm or conferred better resistance on LUTS in more instances than Dahoma extract did. The enhanced durability of LUTS was ranked as follows: Albizia ferruginea > Pertersianthus macrocarpus > Blighia sapida > Sterculia rhinopetala > Amphimas pterocarpoides > Cola gigantean > Celtis zenkeri > Sterculia oblonga > Antiaris Toxicaria > Canarium schweinfurthii. Though extracts showed reduced efficacy with time, indications were that extracts from the heartwood of tropical timber species as that of Teak could be employed to preserve their low durability counterparts. Attempts at fixing extracts permanently in timber should be made. The use of natural organic preservatives is promising if it will be deeply researched.
A Asamoah, C Antwi-Boasiako, K Frimpong-Mensah

Surface Characteristics of Southern pine treated with Eastern red cedar oil
2008 - IRG/WP 08-40393
Treatment of wood with various chemicals play an important role on their surface characteristics including as roughness and hardness for further processing such as finishing and machining. The objective of this study is to evaluate surface roughness of Southern pine (Pinus taeda L.) treated with oil extracted from eastern redcedar (Juniperus viginiana L.). Both tangential and radial surfaces of pine samples were treated two non-pressure methods, namely brushing and cold soaking in the oil. Surface quality of the samples were determined using a stylus technique at the end of each type of treatment. Three roughness parameters, average roughness (Ra), mean peak-to-valley height (Rz), and maximum roughness (Rmax) were used for the quantification of treated surface of the samples. Janka hardness method was also employed to evaluate if there was any effect of treatment on hardness of the samples. Average Ra values of 5.42 µm and 3.67 µm were found for tangential and radial surfaces of 24 hrs soaked samples, respectively. Roughness parameters taken from the surface of control and treated samples did not show any significant difference from each other at 95% confidence level. Average Janka hardness value of radial samples was 2.5 times higher than that of tangential. However, hardness values of control and treated samples also did not show significant difference from each other at above confidence level. Based on the findings of this preliminary study eastern redcedar oil could be considered as alternative treatment chemical for wood products without having any adverse effect on their surface roughness and hardness.
S Hiziroglu

Measurement of wood decay by dynamic MOE in an accelerated soil contact test
2008 - IRG/WP 08-20390
Current laboratory and field testing of preservatives involves various techniques to determine the extent of fungal attack, including visual inspection, mass loss, and static bending and compression strength measurements. The objective of this study was to compare decay measurement by conventional compression strength versus dynamic MOE, employing small wood stakes in an accelerated laboratory soil-contact wood decay test. The maximum decay was generally observed close to the center of the stake. An average correlation of 0.884 was observed between the average compression and dynamic MOE strength losses.
Gan Li, D D Nicholas, T P Schultz

Moisture adsorption isotherms of wood studies using a dynamic vapour sorption apparatus
2009 - IRG/WP 09-20398
Five types of wood including two Malaysian hardwoods acacia mangium (Acacia mangium) and sesenduk (Endospermum malaccense), two temperate softwoods, Sitka spruce (Picea sitchensis), radiata pine (Pinus radiata) and Accoya (commercially modified wood) were studied to determine their moisture sorption behaviour using a Dynamic Vapour Sorption (DVS) apparatus. The isotherm plot for each species tested showed differences in the adsorption and desorption behaviour. The modified wood Accoya had the lowest Equilibrium moisture content (EMC). The hysteresis of Accoya also exhibited the lowest value between the adsorption and desorption isotherms. The data was also analyzed using the Hailwood-Horrobin (HH) model for isotherm fitting and determination of monolayer and polylayer moisture content. Comparison on the number of accessible OH groups in the monolayer as determined by the HH theory did not correspond with that determined using Rowell’s method for any of the samples.
J Zaihan, C A S Hill, S Curling

Evaluation of variables that influence dynamic MOE in wood decay studies
2009 - IRG/WP 09-20409
The effect of wood moisture content (MC) and outdoor exposure of southern pine lap-joint components on dynamic MOE values was investigated. The use of dynamic MOE as a method of measuring progressive biodeterioration of above ground test samples shows promise, but the accuracy of this method for evaluating test samples subjected to fluctuating environmental conditions has not been reported. The results of this study show that fully water saturated samples had consistently lower MOE values than those obtained at lower MC levels. After the MC was reduced from saturation by about 30%, variation in MOE with changes in MC down to the fiber saturation point were minimal. Outdoor exposure of the test samples also influenced the MOE. After an initial period of outdoor exposure, slightly lower MOE values were obtained for all of the test samples. However, subsequent MOE measurements after additional outdoor exposure were fairly consistent and did not show a trend towards either lower or higher values. For some test samples it was not possible to obtain reliable frequency measurements, resulting in their exclusion from the study.
D Nicholas, J Shi, T Schultz

Performance of Fasteners in Treated Wood: A Comparative Study
2009 - IRG/WP 09-40465
Fastener performance is an important property for treated wood. Published data on screw and nail performance for different preservative systems currently on the market are, however, limited. In this study, screw and nail withdrawal strength for southern pine wood treated with ACQ (above ground and ground contact), MCQ (above ground and ground contact), borate (disodium octaborate tetrahydrate – DOT), and untreated southern pine control were tested at air dry and water-soaked conditions based on ASTM standard D1037. Individual sample density and surface hardness were also measured. The relationship among screw and nail withdrawal strength, density, hardness, and moisture content was established for various preservative systems.
Q Wu, T Shupe, J Curole, K Ragon, M Voitier, M Freeman, D Ring

Decay Resistance of Maple (Acer Insigne) Wood Against White Rot
2010 - IRG/WP 10-10740
In this study, the decay resistance of maple (Acer insigne) in natural state and treated with ACC (Acid copper chromate) was investigated against the white rot fungus (Coriolus versicolor). ACC is a kind of water borne preservatives that was used in this study for treating specimens under vacuum and pressure (Bethell procedure) with 3 percent concentration. In conducting mentioned evaluation, kolleschale’s method according to DIN 52176 and B.S. 838: 1961 were used in completely randomized block design. Specimens were contaminated with cultured fungus for fourteen weeks in condition (22, 75% relative humidity). After this period, weight reduction, compressive strength (parallel to grain) and hardness of specimens were tested. Under test conditions weight reduction of control sample were much higher than treated ones. Compressive strength (parallel to grain) and hardness of treated samples were higher than control ones.
V Tazakor Rezaei

Acquisition of sorption isotherms for modified woods by the use of dynamic vapour sorption instrumentation: Principles and Practice
2010 - IRG/WP 10-40518
The complex wood-water relationship has been the topic of numerous studies. Sorption isotherms – in particular – have been derived for hundreds of wood species, their sap- and heartwood sections as well as for decayed, engineered and modified wood materials. However, the traditional methods for obtaining sorption isotherms are very time consuming. With new dynamic vapour sorption (DVS) instrumentation, the acquisition of data for constructing sorption isotherms is suddenly dramatically lowered. Where the traditional methods often required months, data can now be obtained in a matter of days depending on the number of data points required. The fast data acquisition makes DVS a useful tool in studying the sorption properties of wood, and especially in studying the effect of different modification treatments on these properties. This study includes an investigation of the sorption properties of heat treated and acetylated softwood. The results of both are compared with results for untreated softwood, and general remarks regarding the acquisition and interpretation of sorption data are made. It is pointed out that care must be taken when interpreting results such as desorption isotherms not commencing from full water saturation. The sorption properties of heat treated Scots pine (Celloc) and acetylated Radiata pine (Accoya) showed a greater hysteresis effect for the previous than both acetylated and untreated softwood. Furthermore, the effectiveness of the different modification treatments was quantified by the reduction in moisture content relative to untreated Scots pine sapwood. This may be used in future documentation of the resistance of modified wood to fungal decay.
E T Engelund, M Klamer, T Mark Venås

Adsorption boundary curve influenced by step interval of relative humidity investigated by Dynamic Vapour Sorption equipment
2011 - IRG/WP 11-40547
The adsorption of water vapour from dry conditions by Norway spruce sapwood has been investigated using Dynamic Vapour Sorption (DVS) instrumentation. This equipment allows a fast and easy data acquisition as well as enables detailed studies of sorption properties using very small sample masses. In this study, particular focus was paid to the effect of step size on the sorption isotherms. Furthermore, the influence of relaxation of swelling stresses was investigated. This was done by having relative humidity (RH) histories with different RH step sizes and by introducing prolonged periods of conditioning at constant climate. The adsorption isotherms constructed on the basis of acquired sorption data was not significantly influenced by the differences in relative humidity (RH) histories. Thus, for practical purposes a stability criterion of 0.002 %/min was found to be adequate for acquiring wood adsorption isotherms using sample masses around 20-45 mg. The different RH histories did, however, affect the sorption kinetics. The sorption proceeds slower if the sample was conditioned at constant climate for a prolonged period before being exposed to another RH level. This indicates that relaxation of swelling stresses affects the sorption kinetics. During the initial phase of adsorption after changing RH, the moisture uptake was found to be linear with the square-root of time. From sorption and swelling kinetic theory the diffusion coefficient of the wood cell wall could be estimated based on data from the initial phase of the adsorption processes. The diffusion coefficient was found to decrease with increasing RH and to be independent of step size, as expected.
E Tang Engelund, M Klamer, T Mark Venås

Physical properties of Pinus radiata veneers modified with hexamethoxymethyl melamine prepolymers
2011 - IRG/WP 11-40551
Prepolymers containing hexamethoxymethyl melamine and either sucrose (Suc-HMMM) or polyvinyl alcohol (PVA-HMMM) were prepared by acid catalysis under reaction conditions optimised with respect to stiffening effect when introduced into Pinus radiata veneers by vacuum impregnation and cured by hot pressing at 150C. Maximum increases in MOE were 20% for Suc-HMMM (50% WPG), 22% for PVA-HMMM (14% WPG). A 1:1 mixture of the two prepolymerisation reactions (P-H:S-H) produced a maximum 27% increase in MOE (40% WPG) and was stable at ambient temperature for at least 54 days. Veneers vacuum-impregnated with P-H:S-H increased the flatwise MOE and MOR by 32% and 19%, respectively, when used as the two superficial veneers on both sides of 12-ply LVL. Edgewise MOE and MOR increased by 19% and 11% respectively. Smaller increases in stiffness and strength were achieved when four treated veneers were distributed throughout the LVL, or when LVL was produced using twelve treated veneers. Veneers treated by immersion in P-H:S-H at various concentrations, then used as a face veneer in plywood increased surface hardness significantly but formaldehyde emissions of the most useful plywood products exceeded the limit of the F*** classification. MDF manufactured from Pinus radiata fibres treated with P-H:S-H at 10%, 30% and 50% by fibre weight showed a decrease in water-induced weight gain and swelling proportionate to the prepolymer loadings.
C Molloy, W Rae, S Connor, T Henderson, A Siraa

Effect of Nano-silver Treatment on Densified Poplar Wood Properties. Part Two: Spring Back, Compression set, Impact Load Resistance and Hardness
2011 - IRG/WP 11-40568
This paper is the second part of the study of applying nano-silver treatment before densification of poplar wood (Popolus alba). The specimens were prepared in four groups of: 1) nano-silver impregnated 2) water impregnated 3) dried with no impregnation and 4) the control specimens. The impregnation process was done by empty cell process. Then, the groups of 1 to 3 were compressed in a hot press at the temperatures of 150 and 175ᵒc for 1 and 4 hours. Spring-back, compression set, impact load resistance and hardness values of specimens were determined and all data were analyzed statistically. The measurements of mechanical properties were carried out according to ASTM D-143. The results showed that by nano-silver treatment, spring back, compression set and impact load resistance were improved, significantly. The best amounts of spring-back (0.24%) and compression set (35.26%) were seen in specimens which were impregnated with nano-silver solution and compressed at 175 for 4 hours. The best amount of impact load resistance (34915.0 J/m2) belonged to the nano-silver treated specimens which were compressed at 150 for 4 hours. The maximum amounts of hardness values (37.16 N/mm2) were related to the non-treated specimens which were compressed at 175 for 4 hours. On the whole, based on the results of part one and this one, applying nano-silver treatment can be resulted in obtaining optimal physical and mechanical properties in densified poplar wood. The results of this study will be useful for producing a novel densified wood which can be applicable for some structural uses such as flooring.
G Rassam, H Reza Taghiyari, B Jamnani, M Ali Khajeh

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