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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

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

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

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

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

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

Indentation and pendulum hardness tests: two convenient assessment methods of the performance of exterior wood coatings
2015 - IRG/WP 15-40689
Developing formulations of exterior wood coatings with long service life is a big challenge. For many years in Europe the performances have been mainly evaluated through weathering tests (within the EN 927 series) followed by visual assessment (blistering, flaking, mould growth, chalking and cracking), colour and gloss measurements, and adhesion tests. Very recently the importance of the mechanical properties of coatings has been taken into consideration within the CEN/TC 139/WG2 and a test method (CEN/TS 16360) has been suggested to assess the film extensibility by indentation of a coating on a wooden substrate. In 2014 this technical specification was added in the EN 927-2 standard. The aim of this work was to investigate this destructive indentation test for several commercial acrylic coatings applied on spruce and Scots pine. In addition, pendulum hardness tests were carried out as a non-destructive test to gain further information about mechanical properties of the tested coatings. The influence of thickness was examined. This work discusses the advantages and the limits of both methods. They allowed a discrimination of the coatings studied and gave a similar ranking for most of the coatings. The paper also shows the relationship between pendulum hardness variation and long-term performances. Indentation and pendulum hardness tests are shown as useful investigations in addition of the conventional assessment framework of exterior wood coatings.
L Malassenet, L Podgorski, M Truskaller, G Grüll

Increasing the hardness of wood-composite panels by nanosilver
2016 - IRG/WP 16-40715
Effect of silver nanoparticles on hardness in medium-density fiberboard (MDF) was studied here. A 400 ppm aqueous nanosilver suspension was used at three consumption levels of 100, 150, and 200 mL/kg, based on the dry weight of wood fibers; the results were then compared with the control panels. The size range of silver nanoparticles was 30-80 nm. Composite mats were hot-pressed for 6, 8, and 10 min. Results showed that the uniform and even dispersion of nanoparticles throughout the MDF-matrix significantly contributed to an increase in the hardness at lower hot-press time of 6 min. In the longer hot-press times, however, over-heating of the mat resulted in significant a decrease of hardness values. Significant high correlation was observed between water absorption and thickness swelling.
H R Taghiyari, J Norton, K Heidarhaee

Variation in coating hardness during the EN 927-6 weathering test: influence of pigmentation
2016 - IRG/WP 16-40739
The objective of the SERVOWOOD project is to develop and establish European Standards that will facilitate the prediction of service life for exterior wood coatings. Within this project an extensive round robin exercise has been carried out by five partners to establish the repeatability and reproducibility of the EN 927-6 artificial weathering test. This round robin included the exposure of the Internal Comparison Product, a semi-transparent alkyd stain described in EN 927-3, as well as its unpigmented version. Previous studies have shown that Persoz hardness was a useful property to study performance of exterior wood coatings exposed to natural and artificial tests. In this work, in addition of conventional assessment such as cracking and gloss, the Persoz pendulum was used to study hardness variation of the two coatings versus exposure time (from 0 to 12 weeks). Results showed that the exposure led to an increase in hardness for both coatings. However when cracking developed a decrease in hardness was found as cracks probably induced frictional forces on the pendulum which slowed down. For the semi-transparent stain, pigments clearly limited the hardness increase which probably explains that no cracks were found. A slight decrease in hardness was observed for the semi-transparent stain at the end of exposure. It was attributed to the significant change of gloss which may also contribute to slow down the pendulum due to a change in the surface roughness.
L Podgorski, L Malassenet, C Reynaud

Weathering protection of European hardwoods through double modification
2017 - IRG/WP 17-30715
Beech and poplar were thermally modified, treated with melamine resin and both treatments were combined. The weathering performance (cracks and general appearance) of modified beech and poplar was assessed in natural weathering and correlated to material properties such as work in bending (WB) and Brinell hardness. In addition, the equilibrium moisture content after exposure of 12 months and subsequent climatization was evaluated. Melamine treated beech and thermally modified poplar performed best while still showing serious cracks. The melamine treatment increased the equilibrium moisture content, indicating a rather hygroscopic behaviour of the resin. All treated groups showed increased moisture contents after weathering and subsequent climatization. The thermal and melamine treatment decreased the WB substantially. The melamine treatment of the thermally modified wood (double modification) did not further decrease the WB. WB as an indicator of brittleness could not explain the cracking behaviour. Thermal modification decreased the Brinell hardness, whereas melamine treatment increased it. The increased Brinell hardness of melamine treated groups and the double modified groups can be accounted for the stabilized surfaces without erosion.
G Behr, A Gellerich, S Bollmus, H Militz

Gloss and hardness variations as early indicators of wood coating failure during weathering tests
2019 - IRG/WP 19-40866
The objective was to track early changes which ultimately will lead to coating failure when exposed to artificial weathering. Two different coatings (one waterborne acrylic paint and one solventborne alkyd stain) were exposed to artificial weathering for 2016 hours according to EN 927-6. Every 168 hours, samples were removed from the artificial weathering device for assessment (general appearance, gloss, colour, Persoz hardness, cracking). The relation between the visual metrics and the Persoz hardness was studied. Results have shown that the increase in Persoz hardness due to weathering was paralleled by the decrease in gloss. For the first time, and for both coatings, a correlation was established between hardness and gloss often considered as pure aesthetical parameter. This demonstrates that the gloss loss usually observed during weathering tests of coatings is a sign of a change in mechanical properties of polymers. Therefore, a special attention should be given to gloss variations to anticipate cracking development and time for coating maintenance. Two models have been proposed to describe early changes for Persoz hardness and gloss variations. They should be useful to calculate acceleration factors produced by artificial weathering tests for each coating using data from natural weathering tests when available.
L Podgorski

Yellow birch fire-protection using polyelectrolytes complexes
2020 - IRG/WP 20-30755
Fire protection has been a major challenge in wood construction for many years. The demand for high-performance, environmentally friendly treatments respecting the physical and chemical characteristics of the material has been accentuated in recent years. Halogenated fire-retardant (FR) compounds were commonly used from the 70’s for their low-cost and high efficiency. They are able to form radicals when heated, which recombine with high energy radicals such as H or OH disturbing the chain reactions of the combustion, reducing oxidative character of the flame. However, evidence of the toxicity of some halogenated FR has limited their use in Europe since 2010, in Canada and in several states of USA. Therefore, non-toxic alternatives are developed and among them an increasing interest for phosphate compounds is noticed. In that frame, the study of polyelectrolyte complexes (PEC) is at its early stage for wood, but their versatility and eco-friendly character are already appreciated for the fire retardancy of fabrics. This study focuses on the study of the efficiency of polyelectrolyte complexes consisting of polyethylenimine (Mw = 600 g/mol and Mw = 25000 g/mol) and sodium hexametaphosphate to improve the fire behaviour of yellow birch. The samples were prepared by vacuum impregnation or by soaking, allowing relatively large weight gains in a very short time. Cone calorimeter tests revealed that a 20 % reduction in PHRR for a weight gain as low as of 3.5 wt.-% can be achieved. Small-scale Steiner tunnel confirmed the positive aspect of PEC, by reducing flame spreads. Brinell hardness and dimensional stability were also studied to ensure that the treatments are not detrimental on these properties and equilibrium moisture content of the samples were evaluated using dynamic vapor sorption. It was demonstrated that whereas fireproofing results are interesting, some improvements must be made to control the hydrophily of polyelectrolytes complexes that affects the dimensional stability of wood.
M Soula, F Samyn, S Duquesne, V Landry

Evaluation of chemical densification of three hardwood species through in-situ electron beam polymerization
2020 - IRG/WP 20-40893
Hardwoods are the most suitable species for wood flooring for their appearance as well as their hardness. Yet, improving hardness can provide substantial benefit for the wood flooring market. Chemical densification of wood and in-situ polymerization through electron beam technology was chosen to increase hardness of three hardwoods (Yellow birch (YB) (Betula alleghaniensis Britt.), Sugar maple (SM) (Acer saccharum Marshall) and Red Oak (RO) (Quercus rubra L.)). Monomer formulations were chosen for their viscosity. Impregnation was carried out through a simple vacuum process and was followed by 100 kGy electron beam irradiation to allow in-situ polymerization. Successful polymerization was proved by infrared spectroscopy and thermogravimetric analysis. Chemical retention and hardness of densified and reference samples were measured. Chemical retention (CR) varied between the three species being the lowest for porous red oak and the highest for diffuse porous yellow birch. CR also decreased with increasing viscosity of the impregnant for SM and YB. However, viscosity did not affect chemical retention of RO samples. Hardness of wood increased substantially for all treatments and all species and was comparable to that of Jatoba. Densified YB samples showed greater improvement of hardness compared to RO and SM due to higher chemical retention. Results also showed that with low chemical retention, hardness was improved but densified wood hardness is mostly influenced by wood properties. While the three species showed significant hardness improvement, yellow birch seems more suitable for densification.
J Triquet, P Blanchet, V Landry

Thermal spray coatings to protect wood from termites
2020 - IRG/WP 20-40905
Protecting buildings and construction materials against subterranean termites in Europe relies on combined physical and chemical approaches. Buildings can be protected by physical or physico-chemical barriers such as gravel aggregates, steel mesh or plastic films impregnated with insecticides. Wood and wood-based materials are traditionally protected by insecticides applied on the surface or deeply impregnated into wood. However, physical protective systems directly coated on wood have not been developed so far. In this work, different thermal spray-coatings were used as a new physical protection of wood against termites. The coatings were sprayed using a Master Jet flame spray gun. A first coat from pure copper was deposited on all wood samples. Then a top coat was sprayed on the copper coating using Flexicords. Three topcoats were studied: i) pure Al2O3, ii) 87% of Al2O3 with 13% TiO2, iii)75% of Al2O3, 23% of ZrO2 and 2% other. All coated samples were exposed to the attack of European subterranean termites according to EN 118. After 8 weeks of exposure, samples were assessed in comparison with uncoated Scots pine blocks used as controls. Results show that all treatment were effective against termites: at the end of the test, none of the samples was damaged and none of the termites survived. The hardness of these coatings probably explains that termites were not able to damage them.
L Podgorski, H Myalska, A Dinoirjean, M Kutnik

Effect of furfurylation treatment on the performance of three Canadian wood species
2022 - IRG/WP 22-40925
The demand for exterior wood siding is stagnating in North America, partly due to the perception of consumers, architects and contractors regarding their durability and maintenance. Improving attributes such as the dimensional stability of wood is therefore necessary to make it more attractive to consumers. This project aims to assess the performance of Canadian species; white spruce (Picea glauca), trembling aspen (Populus tremuloides) and jack pine (Pinus banksiana) treated by furfurylation. Anti-swelling efficiency (ASE), when exposed to humidity increased by an average of 40 % for white spruce, 44 % for aspen and 27 % for jack pine. In immersion, the furfurylation treatment increased ASE up to an average of 43 % for white spruce, 35 % for aspen and 18 % for jack pine. Modified Brinell and Janka hardness were increased for the furfurylated white spruce and especially furfurylated aspen. Furfurylated wood species showed a high whitening after accelerated UV exposure. However, this color change was reduced by applying a semi-transparent stain on the treated samples. Furfurylation treatment of Canadian wood species shows an interesting potential to improve their performance.
G Boivin, D Schorr

Surface chemical wood densification through in situ electron beam polymerization: description and dose study
2022 - IRG/WP 22-40933
Traditional wood chemical densification processes can be used to improve wood mechanical properties by increasing density of the material throughout its thickness. While mechanical surface densification has heavily been investigated, surface treatments involving impregnation of monomers remain unexplored. This study describes a new material, surface densified through lateral impregnation of acrylate monomers and their in-situ polymerization using high-energy electron beams. Yellow birch (Betula alleghaniensis, Britt.) was surface densified and its morphology was studied using X-Ray density profiles and microtomography. Brinell hardness of densified samples increased while irradiated controls showed lower hardness compared to untreated controls. Effect of electron beam dose was studied at 25, 50 and 100 kGy. Using acetone extraction and GC-MS, residual monomers were found at low dose while degradation of wood was observed ah higher dose using FT-IR. This study demonstrates how carefully choosing the electron beam dose impacts the material in different ways.
J Triquet, P Blanchet, V Landry

Influence of weathering on the mechanical properties and performance of exterior wood coatings
2022 - IRG/WP 22-40951
Three commercial coatings were exposed to artificial (EN 927-6) and natural weathering (EN 927-3) on wood samples. Cracking was visually assessed as well as Persoz hardness. Free films of the same coatings were also exposed to the same weathering tests before their tensile properties were measured. Results show that artificial and natural weathering modified the overall mechanical properties of wood coatings. The elastic modulus and the strength increased whereas the strain at break dramatically decreased from the first hours of exposure. For selecting good performing coatings, our results show that it is useful to consider the variations of the elastic modulus and to calculate the retention of the initial strain at break after weathering instead of considering the strain at break result. A significant increase in the elastic modulus lead to cracking. Coatings performed better when their modulus remained below 400 MPa and their retention in strain at break was higher than 20%. The study shows that short artificial ageing tests (< 500 h) on free films are relevant to highlight changes in strain at break observed in natural weathering. They are therefore a valuable tool in the formulation of high-performance products. The mechanical properties measured using the Persoz hardness test are also interesting to take into consideration in order to anticipate the risk of cracking. For the three coatings, the Persoz hardness increased more or less due to weathering. The results show that coatings with an initial Persoz hardness higher than 80 seconds should not be chosen for wood exposed outdoors because their risk of cracking is higher.
L Podgorski, J-D Lanvin