Besma Bouslimi, Yves Bergeron, Ahmed Koubaa. Regional, Site, and Tree Variations ofWood Density and Growth in Thuja occidentalis L. in the Quebec Forest. 2022. Forests 13(12):1984
Thuja occidentalis L. wood is desirabl, e for wooden structures that require wood density uniformity. Wood density is a wood quality indicator related to numerous morphological, mechanical, physiological, and ecological properties. This study aimed to investigate the regional, site, and tree-to-tree variations of T. occidentalis wood density and growth components through the analysis of X-ray densitometer data. A total of 287 trees were randomly sampled from 11 sites in the Abitibi-Témiscamingue regions in Québec, Canada. The average ring density at breast height was 356 kg m−3, with a small difference between earlywood and latewood (167 kg m−3), indicating a relatively uniform wood. Ring density and width varied significantly between the Abitibi and the Témiscamingue regions, mainly in the juvenile wood. Trees from the Abitibi region showed higher ring density than those in the Témiscamingue region. In contrast, the ring width was higher in the Témiscamingue region. Site, tree, and cambial age significantly (p < 0.001) affected wood density and growth components. However, the largest variation is due to the tree-to-tree variation, accounting for about 15%–31% of the total variation. Compared to ring widths, ring density components showed a considerably smaller tree-to-tree variation and higher variation (7.1%) with cambial age than ring widths (0.6%). Ring width correlated positively and significantly (p < 0.001) with average temperature and annual precipitation, while ring density correlated negatively and significantly (p < 0.001) with average temperature and annual precipitation.
Yves Bergeron, Besma Bouslimi, Ahmed Koubaa. Intra-Ring Variations and Interrelationships for
SelectedWood Anatomical and Physical Properties
of Thuja Occidentalis L.. 2019. Forests 10(4):339
DOI : 10.3390/f10040339
Intra-ring variation in wood density and tracheid anatomical properties and wood property interrelationships were investigated in Thuja occidentalis L. Samples were taken from three stands in Abitibi–Témiscamingue, Quebec, Canada. The structure of T. occidentalis wood is simple, homogeneous and uniform, which is desirable for wooden structures that require wood uniformity. From early- to latewood, cell and lumen diameter decreased, while cell wall thickness increased. These changes led to an increase of the cell wall proportion. Wood ring density and width interrelationships were weaker in mature wood compared to juvenile wood. Earlywood density is the more important in determining mature wood density than latewood density and proportion. Earlywood density explains 92% and 89% of the variation in juvenile and mature wood density, respectively. The negative relationship between ring density and width, although significant, was low and tends to weaken with increasing tree age, thus providing the opportunity for silvicultural practices to improve both growth and wood density. Ring width was positively and strongly correlated to early- and latewood width, but negatively correlated to tracheid length and latewood proportion. Accordingly, increases in ring width produce smaller tracheids and wider earlywood without a corresponding increase in latewood. Practical implications of the results are discussed.
Flavia Braghiroli, Nesrine Hamza, Hassine Bouafif, C.M. Neculita, Ahmed Koubaa. Production, characterization, and potential of activated biochar as adsorbent for phenolic compounds from leachates in a lumber industry site. 2018. Environnemental Research 25(26):26562-26575
DOI : 10.1007/s11356-018-2712-9
There is growing interest in low-cost, efficient materials for the removal of organic contaminants in municipal and industrial effluents. In this study, the efficiency of biochar and activated biochar, as promising adsorbents for phenol removal, was investigated at high (up to 1500 mg L?1) and low concentrations (0.54 mg L?1) in synthetic and real effluents (from wood-residue deposits in Québec), respectively. The performance of both materials was then evaluated in batch adsorption experiments, which were conducted using a low solid/liquid ratio (0.1 g:100 mL) at different phenol concentrations (C0?=?5–1500 mg L?1), and at 20 °C. Activated biochars presented higher phenol adsorption capacity compared to biochars due to their improved textural properties, higher micropore volume, and proportion of oxygenated carbonyl groups connected to their surface. The sorption equilibrium was reached within less than 4 h for all of materials, while the Langmuir model best described their sorption process. The maximum sorption capacity of activated biochars for phenol was found to be twofold relative to biochars (303 vs. 159 mg g?1). Results also showed that activated biochars were more effective than biochars in removing low phenol concentrations in real effluents. In addition, 95% of phenol removal was attained within 96 h (although 85% was removed after 4 h), thus reaching below the maximum authorized concentration allowed by Québec’s discharge criteria (0.05 mg L?1). These results show that activated biochars made from wood residues are promising potential adsorbent materials for the efficient treatment of phenol in synthetic and real effluents.
Sahbi Ouertani, Soufien Azzouz, R. Bahar, Lamine Hassini, Ali Belghith, Ahmed Koubaa. Microwave drying kinetics of jack pine wood: determination of phytosanitary efficacy, energy consumption, and mechanical properties. 2018. European Journal of Wood and Wood Products 76(4):1101-1111
DOI : 10.1007/s00107-018-1316-x
The aims of this study were to determine (1) the effects of microwave irradiation on the drying kinetics of jack pine wood, (2) the phytosanitary efficacy, and (3) the processing energy consumption and mechanical strength of the dried product. Microwave drying experiments were performed at 2.45 GHz frequency and at microwave powers ranging from 300 to 1000 W. Results indicate that higher microwave power and initial wood temperature and lower sample thickness increases the internal sample temperature, improves the drying rate, and reduces both drying time and energy consumption. The microwave irradiation efficacy to sanitize jack pine wood boards was determined in terms of temperature/time combinations based on actual drying kinetics according to standards for phytosanitary measures. The energy required to dry 12 mm thick wood board samples at microwave power ranging from 300 to 1000 W was in the range of 36.4–12.3 MJ/kg of water, respectively, for up to 65% energy consumption savings. The impact of microwave power on the mechanical properties was not statistically significant, although mechanical properties tended to decrease with increasing power. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Mourad Saddem, Hassine Bouafif, Sébastien Migneault, Bernard Riedl, Ahmed Koubaa. Effect of fiber and polymer variability on the rheological properties of wood polymer composites during processing. 2018. Polymers Composites 40(S1):E609-E616
DOI : 10.1002/pc.24909
We investigated the effects of fiber variability, size and content on the fusion characteristics of wood particle-reinforced high-density polyethylene (HDPE). Five types of wood sawdust were used: eastern white cedar, with sapwood, and heartwood treated separately; jack pine divided into wood and bark; and black spruce. Three different fiber length classes were also used. Composite pellets containing wood particles at 25, 35, and 45% by weight with HDPE were made using a co-rotating twin-screw extruder. The pellets were melted and mixed during 7 min in a torque rheometer at 180°C. We also investigated the polymer variation using HDPE, polypropylen (PP), polyvinyl chloride (PVC), and a blend of (80% HDPE+ 20% PP) where wood fiber proportion and length were kept constant. We varied the mixing temperature to reach the melting temperature range of each polymer. Mixing and melting times, maximum torque and stabilized torque were obtained. Adding wood fibers to the HDPE increased processing time and torque energy. At constant fiber length and proportion, torque properties varied with fiber origin. Higher fiber length and proportion increased torque energy and time of stabilization. Thus, using wood fibers with different properties will lead to significant variations in processing, such as in extrusion or injection. The fusion characteristics of wood polymer composite vary among polymers. The PVC showed the highest steady-state torque. The formulation containing a polymer blend of HDPE and PP showed the highest torque energy. This higher torque energy is explained by the interaction of the incompatible polymeric chains of the two thermoplastic polymers. © 2018 Society of Plastics Engineers.
Manel Haddar, Ahmed Elloumi, Cheldy Bradai, Foued Elhalouani, Sébastien Migneault, Ahmed Koubaa. Synergetic effect of Posidonia oceanica fibres and deinking paper sludge on the thermo-mechanical properties of high density polyethylene composites. 2018. Industrial Crops and Products 121:26-35
DOI : 10.1016/j.indcrop.2018.04.075
This study evaluated the reinforcement potential of Posidonia oceanica fibres (POF) and deinking paper sludge (DPS) on the thermo-mechanical properties of high density polyethylene (HDPE) binary and hybrid composites. The weight ratios of the fillers (POF and/or DPS) to the polymer were 0:100; 20:80; 30:70 and 40:60 (wt:wt). Maleated polyethylene (MAPE) was added at a proportion of 3% by weight. The chemical composition, structural and thermal properties and morphology of the fillers were investigated by Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The mechanical (tensile and impact strength) and thermal properties (TGA and Differential Scanning Calorimetry (DSC)) of the binary and hybrid composites were also investigated. Binary and hybrid composite properties depend on the chemical composition of the fillers (POF and DPS), the filler/matrix interfacial adhesion and the POF: DPS ratio. The tensile modulus and strength of the binary and hybrid composites increased with increasing filler content (POF or/and DPS). A better interfacial adhesion between fillers and matrix was achieved in the presence of MAPE. HDPE/POF/MAPE composites achieved the highest tensile modulus and strength with 40% POF. But lower thermal stability, ductility and impact strength were found with the addition of the POF. However, the thermal stability, crystallinity, ductility and toughness improved in HDPE/POF/DPS/MAPE hybrid composites due to the addition of DPS or the substitution of POF by DPS. © 2018 Elsevier B.V.
François Godard, Pierre Rivard, Joël Soucy, Ahmed Koubaa. Rheological behavior of high-density polyethylene (HDPE) filled with paper mill sludge. 2018. Journal of Applied Polymer 135:46484
DOI : 10.1002/app.46484
A comparative study was conducted of composites made with sludge from three different paper mills. Sludges were obtained from a thermomechanical pulp (TMP), a chemico?TMP (CTMP), and a Kraft mill with a feedstock of primarily black spruce. The primary sludge (PS) and secondary sludge (SS) were mixed at two different ratios (PS:SS?=?7:3 and 9:1) and blended with high?density polyethylene (HDPE) at 20%, 30%, and 40% proportion. The blends were tested using plate–plate geometry before subjection to frequency sweep by oscillation rheometry. The storage modulus (G?), loss modulus (G?), and complex viscosity (?*) increased with increasing paper sludge content. Decreasing the PS:SS ratio from 9:1 to 7:3 decreased G?, G?, and ?*. Differential scanning calorimetry showed that sludge addition increased both the melting and crystallization temperature, for a positive effect on crystallinity. Although the behavior of sludge–high?density polyethylene blends differed from that of traditional wood plastic composite made with wood flour, they obtained G?, G?, and ?* values of the same magnitude. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46484.
Azmul Huda, Pierre Périnet, Yves Fortin, Roger E. Hernandez, Ahmed Koubaa, Alain Cloutier. Phenotypic and genotypic correlations for wood properties of hybrid poplar clones of Southern Quebec. 2018. Forests 9(3):140
DOI : 10.3390/f9030140
This study aims to understand the phenotypic and genotypic correlations among wood anatomical, physical, and mechanical properties of hybrid poplar clones. Samples were taken from seven clones grown on three sites in Southern Quebec, Canada. Five trees per clone were randomly sampled from each site to measure anatomical (fiber length, fiber proportion, vessel proportion, fiber wall thickness, tension wood), physical (basic density, volumetric, longitudinal, tangential, and radial shrinkage), and mechanical wood properties (flexural modulus of elasticity (MOE), modulus of rupture (MOR), ultimate crushing strength parallel to the grain). The observed phenotypic and genotypic correlations between these wood properties were moderate to strong, except for fiber length and vessel proportion. Genotypic correlations for all wood properties were higher than for corresponding phenotypic correlations. Furthermore, fiber length showed weak correlations, whereas, vessel proportion showed strongly negative correlations with all other properties. Strong correlations were also found among fiber proportion, fiber wall thickness, basic density, and mechanical properties. Furthermore, results from this study show close genotypic and phenotypic correlations between fiber proportion, fiber wall thickness, and wood density, which consequently affect the mechanical performance of wood products. These findings indicate that there is a substantial opportunity to improve wood quality by selecting several wood properties for different end uses. © 2018 by the authors.
Dexiang Wu, Wei-dan Ding, CuiCui Luo, Abdelkader Chaala, Ahmed Koubaa. Robust DEA to assess the reliability of methyl methacrylate-hardened hybrid poplar wood. 2017. Annals of Operation Research 248 (1-2):515-529
DOI : 10.1007/s1047
We transformed a data envelopment analysis (DEA) optimization model into a robust second-order cone equivalent to immunize against output perturbation in an uncertainty set. The robust DEA framework was then used to assess the effect of a wood hardening treatment using methyl methacrylate (MMA) on selected hybrid poplar clones. Because the performance of MMA-hardened hybrid poplar clones varies across clones, ranking hardened clones is crucial for developing hardening treatments for specific industrial applications. The numerical results demonstrate that the hardening treatment can be optimized by applying the proposed DEA framework to select the best hybrid poplar clone types and the optimal amount of impregnated chemicals.
Claudia B. Caceres, Roger E. Hernandez, Ahmed Koubaa. Effects of log position in the stem and commercial thinning on jack pine chip dimensions produced by a chipper-canter. 2017. European Journal of Wood and Wood Products 75(3): 359-373
DOI : 10.1007/s00107-016-1062-x
Fifteen stems of jack pine (Pinus banksiana Lamb.) coming from three commercial thinned (CT) plots (control, moderate, and intensive thinning) in the Abitibi-Témiscamingue region, Canada, were cross-cut into three 2.4 m length sections: bottom, middle, and top logs. Logs were processed with a chipper-canter at three cutting widths (CW 12.7, 19.1, and 25.4 mm), producing chips and a three faced cant. Chips were assessed by thickness, width, and length. Knot characteristics [total knot number (TKN) and area (TKA)] were assessed in the three cant faces. Growth ring attributes [earlywood density, latewood density (LWD), ring density (RD), earlywood proportion (EWP), ring width, and rings per mm], mechanical properties (shear, splitting, modulus of elasticity and modulus of rupture in bending), and basic density were evaluated on samples obtained within each CW area. The weighted mean chip thickness (WCT) was significantly affected by the log position in the stem (LPS) and CW. WCT increased as CW increased. Jack pine produce thicker chips than black spruce, when processed under the same cutting parameters. Thickness of chips coming from bottom and middle logs was similar due to a greater taper of the bottom log, which slightly increased this dimension. Thickest chips were produced in the top log due to a higher TKA and TKN towards the top of the stem. Multiple linear regressions showed that TKA, CW, and RD were significant predictors of WCT. Chip size distributions were significantly affected by the CT, LPS, and CW. Thinned stands logs appeared to produce smaller chips than natural stand logs. Moreover, chip thickness distribution was affected primarily by TKA and EWP, while the width and length distribution was mainly affected by EWP, LWD, and TKN. Chip size in jack pine is to some degree determined by knot attributes, growth ring characteristics, and wood density of the raw material. These results suggest the potential advantage of sorting logs prior to chipping, either by species, LPS and/or provenance (thinned or natural stands).
François Godard, Bernard Riedl, Joël Soucy, Pierre Rivard, Ahmed Koubaa. Étude du comportement rhéologique des composites bois-polymères chargés de résidus papetiers. 2016. Rhéologie 30:1-15
Tikou Belem, Babak Koohestani, Bruno Bussière, Ahmed Koubaa. Experimental investigation into the compressive strenght development of cemented backfill containing Nano-silica. 2016. Cement and Concrete Composites 72:180-189
DOI : 10.1016/j.cemconcomp.2016.06.016
This paper investigates the influence of Nano-silica (NS) addition on the consistency and compressive strength development of cemented paste backfill (CPB). Tetraethyl-Orthosilicate (TEOS) was used as the precursor of Nano-silica along with ether-based Polycarboxylate superplasticizer (PCS). Two binder types (Portland cement and Slag-cement) and different amounts of TEOS (0.7–14% by mass of binder) with and without PCS are examined for 3, 7, 14, and 28 days curing time. Uniaxial compression tests for unconfined compressive strength (UCS) determination, slump height measurement, changes in gravimetric water content, and differential thermogravimetric analysis (DTG) were used to assess the influence of NS and admixtures (TEOS-PCS) on CPB performance. The results of this experimental study indicate that the addition of approximately 5% TEOS along with 0.5% PCS (by mass of binder) provide the best compressive strengths that can also be anticipated through the higher amount of calcium silicate hydrate (CSH) on DTG curves. It is also noticeable that the positive influence of NS is more evident when the amount of binder was decreased. The addition of PCS to CPB containing NS improved both the consistency of the mixture and the compressive strength development of CPB.
Babak Koohestani, Tikou Belem, Bruno Bussière, Hassan Bouzahzah, Ahmed Koubaa. Experimental investigation of mechanical and microstructural properties of cemented paste backfill containing maple-wood filler. 2016. Construction and Building Materials 121:222-228
DOI : 10.1016/j.conbuildmat.2016.05.118
This experimental study investigates the influence of maple-wood sawdust addition on the mechanical and microstructural properties of cemented paste backfill (CPB). Mechanical properties of CPB were determined by uniaxial compressive strength (UCS) tests and microstructural changes were evaluated by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) analysis. Results indicate that the addition of 12.5% maple-wood sawdust (by dry mass of binder) improves the strength development of CPB specimens at later hydration age (91 curing days). However, at a higher maple-wood sawdust content of 14.5%, the UCS showed lower improvement. Moreover, MIP and SEM analysis results revealed that the 12.5% wood filler addition made the CPB material less porous and more compact by increasing the mineral content formed by cement hydration. The positive influence of maple-wood sawdust on CPB was associated with higher binder content (?5%) and mid- to long-term curing times (?56 days).
Manel Haddar, Ahmed Elloumi, Cheldy Bradai, Foued Elhalouani, Sébastien Migneault, Ahmed Koubaa. Effect of high content of deinking paper sludge (DPS) on the reinforcement of HDPE. 2016. Journal of Polymers and the Environment 25(3):617-627
DOI : 10.1007/s10924-016-0837-9
Deinking paper sludge (DPS)/high density polyethylene (HDPE) composites with and without coupling agent (3 % of maleated polyethylene (MAPE)) were manufactured by twin-screw extrusion followed by injection molding with high percentages of DPS (0, 20, 30 and 40 %). The effects of DPS content and MAPE on the mechanical, thermal, and morphological properties of the DPS/HDPE composites were investigated. Increasing DPS content in composites increased the tensile and flexural modulus (E; MOE), tensile and flexural strength (Rm; MOR), while decreased elongation at break and Un-notched impact resistance due to a poor adhesion between the DPS and HDPE. The addition of DPS also improved the thermal stability and increased the composites crystallinity. High content of DPS (40 %) and 3 % MAPE achieved good interfacial adhesion between fibres of DPS and HDPE. Therefore, an increase is observed for Rm, MOR, ductility, and impact toughness.
Claudia B. Caceres, Svetka Kuljch, Roger E. Hernandez, Ahmed Koubaa. Effects of commercial thinning, log position in the stem, and cutting width on the surface quality of cants produced by a chipper-canter. 2016. Wood Material Science and Engineering. 1-8
DOI : 10.1080/17480272.2016.1232308
Fifteen stems of jack pine (Pinus banksiana Lamb.) of 3 commercial thinned plots (control, moderate, and intensive thinning) and 15 stems of black spruce (Picea mariana (Mill.) B.S.P), both coming from the Abitibi-Témiscamingue region – Canada, were cross-cut into three 2.4?m length sections: bottom, middle, and top logs. Logs were processed with a chipper-canter at three cutting widths (12.7, 19.1, and 25.4?mm), producing chips and a three-faced cant. The middle section of the cant was used to evaluate surface quality across the grain on each face. Roughness and waviness parameters and depth of torn grain were recorded. Knot characteristics were assessed in the three cant faces. Poorer surface quality was found in the lower part compared to the upper part of the cant for both species. At larger cutting widths, jack pine logs coming from a natural stand showed lower surface quality compared to logs from thinned stands. Black spruce waviness increased with the cutting width and stem height. These results were attributed to the increase of forces and vibration when cutting at larger cutting widths, which was worsened by the presence of bigger, more numerous knots at the control plot and in the top logs. Black spruce had deeper torn grain compared to jack pine. Their differences in knot characteristics resulted in a maximum torn grain depth favored by the presence of more knots rather than by bigger knot size. Other knot characteristics, such as the position of the knots in the cant face, the insertion angle of the branch and the distribution of the knots around the log, should be studied to better understand the relationship between torn grain formation and knottiness.
Jessica Smith, Brian Harvey, Marc Mazerolle, Ahmed Koubaa. Sprucing up the mixedwoods: Growth response of white spruce (Picea glauca) to partial cutting in the eastern Canadian boreal forest. 2016. Can. J. For. Res. 46(10):1205-1215
DOI : 10.1139/cjfr-2015-0489
Mixed species stands present a number of opportunities and challenges to forest managers. Boreal mixedwood stands in eastern Canada are often characterized by a canopy of shade intolerant aspen (Populus tremuloides) with more shade tolerant conifers in the sub-canopy layers. Because the aspen and conifers often attain optimal merchantable sizes at different moments, there is an interest in developing silvicultural practices toremoval of aspen and favour accelerated growth of residual conifers. We tested three partial harvesting treatments in mixed aspen - white spruce (Picea glauca) stands in which different proportions of aspen (0, 50, 65 and 100% basal area) were removed. Ten years after treatments, 72 spruce stems destructively sampled for stem analysis. Using linear mixed effect models, we analyzed growth as a function of treatment intensity, time since treatment, social status, pre-treatment growth rate, and neighbourhood competition. Relative to control stands, radial and volume growth responses were detected only in the extreme treatment of 100% aspen removal. In relative terms, suppressed trees showed the greatest magnitude of cumulative growth increase. Growth response was proportional to pre-treatment growth rate and, among neighbouring trees, only coniferous neighbours had a negative effect on white spruce growth.
Julien Moulinier, Suzanne Brais, Brian Harvey, Ahmed Koubaa. Response of boreal jack pine (Pinus banksiana lamb.) Stands to a gradient of commercial thinning intensities, with and without N fertilization. 2015. Forests 6(8):2678-2702
DOI : 10.3390/f6082678
This study examines tree and stand response to a gradient of commercial thinning intensities and nitrogen fertilization (200 kg N ha?1) in nine jack pine (Pinus banksiana) stands of Eastern Canada over a period of 14 years. Thinning intensity ranged from 0% basal area removal in control plots to 64% in thinned plots. Tree diameter increment, absolute and relative volume increment and mean volume increased with thinning intensity and were higher in fertilized plots. Individual tree response depended on tree diameter, with smallest trees exhibiting highest relative volume increment to thinning intensity. Stand basal area increment was positively associated to initial stand basal area and negatively to stand age. In thinned and fertilized plots, stand volume increment was higher and natural mortality lower than in fertilized only and unfertilized control plots over the 5–14 year period after thinning. However, the positive effect of fertilization on tree volume increment decreased with thinning intensity. Despite positive individual tree growth responses to thinning and fertilization, residual stand volume increment decreased with increased thinning intensity in both fertilized and unfertilized plots. While total cumulative stand volume (harvested + residual) also decreased with thinning intensity in unfertilized plots, comparable total volumes were observed in fertilized + thinned and unthinned control plots. Nitrogen fertilization in the years following commercial thinning enhanced the benefit of thinning on these relatively poor sites by increasing tree diameter growth, lowering mortality, and increasing total stand merchantable volume compared to unfertilized thinned stands.
Martin Payette, Pascal Drouin, Timothy Work, Ahmed Koubaa. Efficacy of microwave irradiation for phytosanitation of wood packing materials. 2015. Industrial Crops and Products 69:187-196
DOI : 10.1016/j.indcrop.2015.01.030
Wood packing materials (WPM) are important vectors of invasive xylophagous insects and pathogenic and decomposer wood fungi. The International Plant Protection Convention introduced the International Standards for Phytosanitary Measures No. 15 (ISPM No. 15) to regulate the development of treatments to sanitize WPM and prevent the introduction and movement of forest pests. Dielectric heating (e.g., microwave irradiation) has recently been included as an accepted treatment. In this study, the efficacy of microwave irradiation was tested on Monochamus scutellatus larvae and on four different pathogenic fungi, Gremmeniella abietina, Heterobasidion annosum, Chondrostereum purpureum, and Mycosphaerella populorum, five species of economic significance in Québec, in both jack pine and trembling aspen. We explored different temperature/time combinations on each species in order to accumulate data on the treatment. We irradiated M. scutellatus larvae at 56, 61, and 66. °C for 1-3. min and the four fungal species at 50, 55, 60, 65, 70, 75, and 90. °C for 0.5, 1, or 2. min. Fungi were tested at a wider range of temperatures to account for possible higher variation of resistance between species. We obtained 100% mortality in larvae treated at 56. °C for 2. min and at 61. °C for 1. min. The fungi species were much more resistant to the treatment. G. abietina was eliminated at 75. °C/0.5. min, H. annosum at 90. °C/1. min, M. populorum at 90. °C/2. min, and C. purpureum was still present at the highest temperature/time combination used. We demonstrated the capacity of microwave irradiation to kill the larvae with similar parameters as IPPC guidelines (60. °C for 1. min), though lethal temperatures for the fungi were very high. As the current ISPM No. 15 standard for microwave irradiation was insufficient to kill all tested fungal species, more work should be done on determining optimal combinations for the greatest number of species. Future studies should test a wider range of treatment times and expand trials to include more insect and fungal species to determine which temperature/time combination will allow us to keep both values as low as possible while assuring complete prevention of adult insect emergence and fungal re-growth.
Cyriac-Serge Mvolo, Jean Beaulieu, Marc Mazerolle, Alain Cloutier, Ahmed Koubaa. Variation in wood quality in white spruce (Picea glauca (Moench) Voss). Part I. defining the juvenile-mature wood transition based on tracheid length. 2015. Forests 6(1):183-202
DOI : 10.3390/f6010183
Estimations of transition age (TA) and juvenile wood proportion (JWP) are important for wood industries due to their impact on end-product quality. However, the relationships between analytical determination of TA based on tracheid length (TL) and recognized thresholds for adequate end products have not yet been established. In this study, we used three different statistical models to estimate TA in white spruce (Picea glauca (Moench) Voss) based on TL radial variation. We compared the results with technological maturity. A two-millimeter threshold, previously suggested for good paper tear strength, was used. Tracheid length increased from pith to bark and from breast height to upper height. Juvenile wood (JW) was conical with the three models. At breast height, TA ranged from 11 to 27 years and JWP ranged from 15.3% to 47.5% across the three models. The linear mixed model produced more conservative estimates than the maximum-quadratic-linear (M_Q_L) model. Both the linear mixed model and the M_Q_L model produced more conservative TA estimates than the piecewise model. TA estimates by the MIXED model, and to a lesser extent by the M_Q_L model, were equivalent to those for real mature wood, whereas TA estimates by the piecewise model were considerably lower, falling into the transition wood area.
Yves Bergeron, Ahmed Koubaa, Besma Bouslimi. Anatomical properties in Thuja occidentalis: Variation and relationship to biological processes. 2014. IAWA 35(4):363-384
The variability in wood properties of eastern white cedar (Thuja occidentalis L.) is relatively poorly known. Here we report the axial and the radial variation in selected anatomical properties, namely, ring width, wood density, and tracheid length and width. Forty-five trees were randomly sampled and felled from three selected sites in the Abitibi-Témiscamingue region, Quebec, Canada. Disks were systematically sampled at 0.5, 1.3, and 3 m stem height and at every 2 meters thereafter up to the tree top. Average ring density at breast height was 355 kg/m³ with a small difference between earlywood and latewood. The latewood proportion was uniform and constant within the tree at about 32%. The tracheids were fine and long, averaging 25.3 ?m in width and 2.07 mm in length. The variation in wood density components between trees was highly significant. The cambial age effect on all measured properties was highly significant. Ring density decreased from a maximum near the pith to a minimum in the juvenile–mature wood transition zone and remained constant or decreased slightly thereafter. Annual ring width decreased from a maximum near the pith to a minimum at the 10th ring and increased thereafter. Tracheid length and width showed typical radial variation characterized by a steady increase from pith to bark. Within-tree axial variation was highly significant, but ring width showed more substantial changes. Changes in wood properties with height depend on cambial age and thus are implied since the proportion of juvenile wood in the stem increases from the base to the top.
Azmul Huda, Yves Fortin, Roger E. Hernandez, Alain Cloutier, Ahmed Koubaa. Variation of the physical and mechanical properties of hybrid poplar clones. 2014. BioResources 9(1):1456-1471
Roger E. Hernandez, Angela M. Llavé, Ahmed Koubaa. Effects of cutting parameters on cutting forces and surface quality of black spruce cants. 2014. European Journal of Wood and Wood Products 72(1):107-116
DOI : 10.1007/s00107-013-0762-8
The effects of rake angle, cutting direction, and depth of cut on cutting forces and surface quality of black spruce were evaluated. Cutting forces were measured during cutting at four rake angles (35, 45, 55 and 65), four cutting directions (0 -90, 15 -75, 30 -60, and 45 -45), and three depths of cut (1, 2, and 3 mm). Torn grain, waviness, and roughness were evaluated. The results showed that as rake angle increased, cutting forces, torn grain, waviness, and roughness decreased. The lowest cutting forces and the best surface quality were obtained with 65 of rake angle. At this angle, cutting forces and surface quality were more affected by depth of cut than by cutting direction variations. Thus, as depth of cut decreased, the effects of cutting orientation on the cutting forces and surface quality decreased. The application of these results to the canting work of a chipper-canter is analyzed. © 2013 Springer-Verlag Berlin Heidelberg.
Sahbi Ouertani, Soufien Azzouz, Lamine Hassini, Ali Belghith, Ahmed Koubaa. Moisture sorption isotherms and thermodynamic properties of Jack pine and palm wood: Comparative study. 2014. Industrial Crops and Products 56:200-210
DOI : 10.1016/j.indcrop.2014.03.004
Currently, the impact of the controlled climate on moisture sorption isotherms of Jack pine and palm wood still remains unclear. The aim of this paper was to determine and compare the moisture sorption isotherms and thermodynamic properties of Jack pine and palm wood. The equilibrium moisture content of wood samples was measured within the range of 5 to 90% relative humidity at 50. °C, 60. °C, 70. °C and 80. °C. For both wood varieties, the equilibrium moisture content decreased with increasing temperature, however the effect of temperature is very remarkable for palm wood. The isosteric heat of desorption, the enthalpy and the entropy decreased with the increase of the moisture content. A good straight line correlated differential enthalpy and entropy, according to the enthalpy-entropy compensation theory. The spreading pressure decreased with increasing temperature at a given water activity, and increased with increasing water activity at a constant temperature. Predictive correlations of the two wood properties, based on experimental methods and physical laws, were established and compared. © 2014 Elsevier B.V.
Joël Soucy, Sébastien Migneault, Bernard Riedl, Ahmed Koubaa. The potential of paper mill sludge for wood-plastic composites. 2014. Industrial Crops and Products 54:248-256
DOI : 10.1016/j.indcrop.2014.01.013
Recent studies have demonstrated the potential of primary sludge (PS) as reinforcing fibers and secondary sludge (SS) as binder or co-binder in wood–plastic composites (WPC). A comparative study was conducted using paper mill sludge produced by three different pulping processes at two SS to PS ratios. The objectives were to determine the impact of PS and SS on the development of high density polyethylene (HDPE) WPC properties. Sludge produced by thermomechanical pulping (TMP), chemithermomechanical pulping (CTMP), and Kraft pulping were used at three different proportions (20%, 30%, and 40%) for composite manufacturing. The use of mixed sludge containing 30% SS resulted in lower tensile, flexural, and impact performance of the WPC compared to mixed sludge containing only 10% SS for the three pulping processes. Sludge type had a significant impact on the WPC physical and mechanical properties. Kraft sludge produced the best WPC properties, followed by CTMP and TMP sludge. Increasing the sludge proportion produced increasingly negative impacts on water absorption and thickness swelling, but improved the flexural and tensile properties.
Sébastien Migneault, Patrick Perré, Ahmed Koubaa. Effect of fiber origin, proportion, and chemical composition on the mechanical and physical properties of wood-plastic composites. 2014. Journal of Wood Chemistry and Technology. 34(4):241-261
DOI : 10.1080/02773813.2013.869604
This study assessed the potential of wood residues as fiber sources for wood-plastic composites (WPC) and examined the impact for intrinsic fiber properties on strength development. Sawmill sawdust, underused wood species, bark, composite panel, and pulp and paper sludge residues were sampled. Fibers were characterized for cellulose content, ash content, and fiber aspect ratio. WPC samples were formed by twin-screw extrusion compounding, followed by injection molding at three fiber proportions. WPC mechanical properties, water uptake, and water swelling increased with increasing fiber proportion, whereas tenacity decreased. WPC made with residues had lower mechanical and physical properties than those made with clean wood, with some exceptions. Kraft sludge produced one of the best WPC formulations in terms of thickness swell, water swelling, tensile strength, and impact energy. Deinking sludge produced the toughest and the most dimensionally stable WPC. Panel industry residues formed roughly similar WPC to those made with clean wood. Bark led to poorest WPC in terms of mechanical properties. High correlation coefficients were found between cellulose content, wood content, and all WPC properties except impact energy. However, the correlations between aspect ratio and the WPC were insignificant. © 2014 Copyright Taylor & Francis Group, LLC.
Yves Bergeron, Besma Bouslimi, Ahmed Koubaa. Effects of biodegradation by brown-rot decay on selected wood properties in eastern white cedar (Thuja occidentalis L.). 2014. International Biodeterioration & Biodegradation 87:87-98
DOI : 10.1016/j.ibiod.2013.11.006
The effects of decay on wood density, wood structure, chemical composition, and mechanical properties in eastern white cedar (Thuja occidentalis L.) were investigated. Decay stage was determined by X-ray densitometry and scanning electron microscopy (SEM). Chemical and mechanical properties of decayed and sound wood samples were also determined. SEM results showed that decay colonization varied among wood cell types and within individual cell wall layers. Growth of fungi causing brown rot decay was limited and slower in latewood than in earlywood due to the narrow cell lumen, thicker wall, and higher density of latewood. Decay-related changes in wood density were more prominent in earlywood than latewood tracheids. Brown-rot decay selectively removes structural carbohydrate components, increasing the higher lignin/carbohydrate ratio as decay progresses. The relationships between chemical composition, mechanical properties, and weight loss were highly significant, with 15% weight loss leading to 40% loss in modulus of rupture (MOR) and 30% loss in bending modulus of elasticity (MOE). The strength loss (MOR) was attributable to arabinan and galactan loss. The loss in wood stiffness was associated with cellulose (glucan) loss, and weight loss was associated with mannan and xylans losses.
Pierre Cartier, Ahmed Koubaa. Le bois, tout feu, mais pas toute flamme
Vers la construction multiétage en toute sécurité 2013. Le Couvert Boréal 12
Pierre Cartier, Ahmed Koubaa. IMPLICATIONS PRATIQUES DE LA SYLVICULTURE INTENSIVE SUR LA QUALITÉ DU BOIS 2013. Le Couvert Boréal 30
Samia Belkhir, Ayda Khadhri, Mustapha Ksontini, Hamid Nadji, Samira Smiti, Tatjana Stevanovic, Ahmed Koubaa. Seasonal effect on the chemical composition of the leaves of Stipa tenacissima L. and implications for pulp properties. 2013. Industrial Crops and Products 44:56-61
DOI : 10.1016/j.indcrop.2012.09.023
Esparto (Stipa tenacissima) is a highly fibrous herbaceous plant. In addition, the fiber properties (suppleness, thinness, and cellulose content) make this plant a valuable raw material for papermaking in terms of both quality and quantity. In Tunisia, esparto is the only source of raw material for papermaking. In this paper, the chemical characteristics (cellulose, hemicelluloses, lignin, extractives, and ashes) of esparto leaves are analyzed in relation to growing conditions and plant biology. Four localized sites in the Kasserine region (central Tunisia) are examined. The chemical properties of esparto fibers vary significantly with site and season. In fall, esparto leaves contain more cellulose (46.4%) than in other seasons. In winter, esparto leaves have lower cellulose content (43.3%) and higher extractive content. The pulp properties across seasons indicate that pulp yield and strength properties are superior when leaves are harvested in fall.
Patrice Soulonganga, Martin Claude Ngueho Yemele, Michael P. Wolcott, Tatjana Stevanovic, Alain Cloutier, Ahmed Koubaa. Effects of hot water treatment of raw bark, coupling agent, and lubricants on properties of bark/HDPE composites. 2013. Industrial Crops and Products 42(1):50-56
DOI : 10.1016/j.indcrop.2012.05.012
Hot water treated and untreated black spruce bark (BSB) and trembling aspen bark (TAB) fibers were combined with high density polyethylene (HDPE) to produce bark thermoplastic composites by extrusion. Bark fibers of three size categories (fine, medium, and coarse) were used at contents of 50% and 60% based on oven dry weight. The effects of hot water treatment of raw bark and the addition of coupling agent (MAPE) and lubricants (OP-100, talc) on the flexural and tensile properties of bark/HDPE composites were investigated. Results showed a significant impact of hot water treatment on tensile properties of composites made with BSB and on tensile and flexural strength of composites made with TAB. The addition of coupling agent and lubricants significantly improved the flexural and tensile strength properties of bark/HDPE composites but reduced toughness and strain.
Svetka Kuljch, Roger E. Hernandez, Angela M. Llavé, Ahmed Koubaa. Effects of cutting direction, rake angle, and depth of cut on cutting forces and surface quality during machining of balsam fir. 2013. Wood and Fiber Science 45(2):196-205
Effects of cutting direction with respect to grain angle, rake angle, and depth of cut on cutting forces and surface quality during machining of balsam fir were evaluated. These factors were analyzed within a perspective of their application to a chipper-canter machining process. Balsam fir is one of the most important boreal species in Canada and is widely used in the pulp and paper industry and construction applications. Wood samples prepared at four cutting directions (0-90°, 15-75°, 30-60°, and 45-45°) were machined using four rake angles (35, 45, 55, and 65°) and three cutting depths (1, 2, and 3 mm). Results showed that rake angle was the most important factor affecting cutting forces and surface quality. Furthermore, as rake angle increased, the effect of cutting direction and depth of cut on cutting forces and surface quality became less important. At 65° rake angle, cutting forces decreased and surface quality increased as depth of cut passed from 3 to 1 mm. Surface quality also improved as cutting action changed from the 0-90° to 45-45° direction. The results gave useful information for improving the performance of the chipper-canter in terms of surface quality and energy consumption. © 2013 by the Society of Wood Science and Technology.
Hassine Bouafif, Patrick Perré, Alain Cloutier, Ahmed Koubaa. Creep behaviour of HDPE/wood particle composites. 2013. International Journal of Microstructure and Materials Properties 8(3):225-238
DOI : 10.1504/IJMMP.2013.055385
The effect of particle type, size, content and manufacturing process on the creep behaviour of wood particles/High Density Polyethylene (HDPE) composites has been investigated. Short-term creep tests at different temperatures were carried out and modelled using the Bürger's model and the Findley power law. The creep of the composites was found to increase with temperature due to the mobility of the amorphous bulk and tie HDPE molecules. Increased wood particle content generally decreased the creep level. Jack pine composites exhibited the highest creep reduction due to the chemical composition of the fibres surface and the efficiency of adhesion mechanism between fibres and the HDPE. Injection and compression processes led to better creep behaviour than the extrusion process due to differences in the composites microstructures. Particle size did not show important impacts on the creep properties. Findley power law led to better prediction of long time creep behaviour of the composites.
Fouad Erchiqui, Z. Annasabi, F. Slaoui-Hasnaoui, H. Kaddami, Ahmed Koubaa. Numerical modelling of microwave heating of frozen wood. 2013. Can. J. Chem. Eng. 91(9):1582-1589
DOI : 10.1002/cjce.21826
The heating process of frozen wood exposed to plane microwaves is numerically investigated. The nonlinear heat conduction problem involving phase change such as wood freezing is solved by a specific 3D volumetric enthalpy-based finite element method. Dielectric and thermal properties are a function of temperature and moisture content. The numerical model is validated by experimental and analytical means. As an application, we studied the effect of moisture content and frequency on microwave heating of trembling aspen wood.
Suying Xing, Bernard Riedl, James Deng, Hamid Nadji, Ahmed Koubaa. Potential of pulp and paper secondary sludge as co-adhesive and formaldehyde scavenger for particleboard manufacturing. 2013. European Journal of Wood and Wood Products 71(6):705-716
DOI : 10.1007/s00107-013-0729-9
This study investigated the potential of secondary sludge (SS) as urea–formaldehyde (UF) co-adhesive for particleboard manufacturing. Three proportions of SS from three conventional pulping processes were added in the formulation of particleboard manufacturing. A 33 factorial design was used. All panels were tested for thickness swell (TS), linear expansion (LE), internal bond strength (IB), flexural modulus of elasticity (MOE), flexural modulus of rupture (MOR) and formaldehyde emission. Results indicated that particleboards made with SS from thermomechanical pulp (TMP) and kraft pulp (Kraft) met the ANSI standards for LE, IB, MOE, and MOR (with 7 and 9 % UF). However, the TS of panels made with SS was higher than that of control panels and adding SS to the formulation affected negatively this property. Most of the properties studied in the particleboards made with SS from chemical–thermomechanical pulping (CTMP) process failed to meet the ANSI standards. The main advantage of using SS as co-adhesive is the reduction of formaldehyde emission, in the best case here, about 50 %, with CTMP sludge added, of the particleboards.
Besma Bouslimi, Yves Bergeron, Ahmed Koubaa. Variation of brown rot decay in eastern white cedar (Thuja occidentalis L.). 2013. BioResources 8(3):4735-4755
Variations in brown rot decay and proportions of heartwood and sapwood were investigated in eastern white cedar (Thuja occidentalis L.). This experiment tested the hypothesis that the incidence of brown rot decay depends on the site, tree age, tree height, and heartwood/ sapwood ratio. Forty-five trees were sampled and felled from three mature stands in the Abitibi-Témiscamingue region, Quebec, Canada. From each tree, disks were systematically sampled along the entire stem, and the heartwood, sapwood, and decay proportions and volumes were determined for each disk. Scanning electron microscopy showed that growth of fungi causing brown rot decay was limited and slower in latewood than in earlywood due to the narrow cell lumen, thick wall, and limited number of bordered pits in latewood tracheids. Site, tree height, and tree age had significant effects on the proportions of sapwood, heartwood, and decay. Heartwood and brown rot decay proportions decreased from the base of the tree upward, while the sapwood proportion increased. There was more decay in older trees and in those growing on moist versus dry sites; however, decay was not serious in trees younger than 80 years. In addition, brown rot decay proportion correlated strongly and positively with heartwood proportion and tree volume, but negatively with sapwood proportion.
Wei-dan Ding, Abdelkader Chaala, Ahmed Koubaa. Mechanical properties of MMA-hardened hybrid poplar wood. 2013. Industrial Crops and Products 46:304-310
DOI : 10.1016/j.indcrop.2013.02.004
Wood of fast-growing hybrid poplars, consisting of six 6-year-old clones in one plantation in Quebec, was impregnated with methyl methacrylate (MMA) and then polymerized by heat/catalyst method. The mechanical properties (static bending and compressive strength) of poplar clones and its MMA-hardened wood were investigated. Significant differences were observed among clones in bending and compression strength parallel to grain. Hardening treatment has also considerably improved all strength properties except for strain at rupture in static bending. The effects of density on mechanical properties were inconsistent, especially for hardened wood. Density was not the most important factor affecting strength properties. The improved properties of MMA-hardened hybrid poplar were comparable to some commercial hardwood species.
Azmul Huda, Roger E. Hernandez, Alain Cloutier, Ahmed Koubaa. Anatomical properties of selected hybrid poplar clones grown in southern Quebec. 2012. BioResources 7(3):3779-3799
The anatomical properties of seven hybrid poplar clones grown in three sites in southern Quebec, Canada were investigated. Radial and longitudinal variations in selected anatomical properties of wood were measured by image analysis of transverse sections and by fiber quality analysis. Results indicate that all measured anatomical properties varied significantly across sites. Clonal variation was highly significant for all anatomical properties studied, and broad-sense heritability ranged from 0.10 (average vessel lumen area) to 0.76 (cell wall area percentage). Genetic gain was positive for all anatomical properties. The variation in radial pattern was characterized by a rapid increase in the first few years in fiber length, width, and proportion, wall thickness, and percent cell wall area. Ray proportion remained constant, whereas the vessel lumen area and proportion decreased with cambial age.
Wei-dan Ding, Abdelkader Chaala, Ahmed Koubaa. Dimensional stability of methyl methacrylate hardened hybrid poplar wood. 2012. BioResources 7(1):504-520
In an effort to achieve high mechanical performance and improved dimensional stability, densification combined with oil-heat treatment (OHT) was performed. In our previous study, OHT was successfully applied to densified veneer, which resulted in improved dimensional stability. In the present study, the impact of OHT on densified wood veneer hygroscopicity and mechanical properties was determined. OHT at 180, 200, and 220ºC for 1, 2, and 3 hours was applied to densified Aspen (Populus tremuloides) veneers. OHT was found to be an efficient treatment to reduce the hygroscopicity of densified aspen veneers, although OHT had a negative impact on Brinell hardness. However, due to the contribution of densification, the hardness of oil-heat treated veneers was still two to three times higher than that of non-densified veneers. Similar results were found for tensile strength. Bending strength increased slightly at low OHT temperature, and then decreased at high temperature. Bending strength of oil-heat treated densified veneer samples was higher than that of non-densified ones. No significant effect of OHT was found on tensile MOE, but bending MOE increased after OHT. Compared to OHT duration, OHT temperature had a larger impact on densified wood hygroscopicity and mechanical properties.
Alain Cloutier, Changhua Fang, Pierre Blanchet, Ahmed Koubaa. Densification of wood veneers combined with oil-heat treatment. part 2: hygroscopicity and mechanical properties. 2012. BioResources 7(1):925-935
In an effort to achieve high mechanical performance and improved dimensional stability, densification combined with oil-heat treatment (OHT) was performed. In our previous study, OHT was successfully applied to densified veneer, which resulted in improved dimensional stability. In the present study, the impact of OHT on densified wood veneer hygroscopicity and mechanical properties was determined. OHT at 180, 200, and 220ºC for 1, 2, and 3 hours was applied to densified Aspen (Populus tremuloides) veneers. OHT was found to be an efficient treatment to reduce the hygroscopicity of densified aspen veneers, although OHT had a negative impact on Brinell hardness. However, due to the contribution of densification, the hardness of oil-heat treated veneers was still two to three times higher than that of non-densified veneers. Similar results were found for tensile strength. Bending strength increased slightly at low OHT temperature, and then decreased at high temperature. Bending strength of oil-heat treated densified veneer samples was higher than that of non-densified ones. No significant effect of OHT was found on tensile MOE, but bending MOE increased after OHT. Compared to OHT duration, OHT temperature had a larger impact on densified wood hygroscopicity and mechanical properties.
Changhua Fang, Nicolas Mariotti, Alain Cloutier, Pierre Blanchet, Ahmed Koubaa. Densification of wood veneers by compression combined with heat and steam. 2011. European Journal of Wood and Wood Products 70(1-3):155-163
DOI : 10.1007/s00107-011-0524-4
Wood veneer 700×700 mm2 specimens made with aspen (Populus tremuloides) and hybrid poplar clone 15303 (Populus maximowiczii × Populus balsamifera) were densified using heat, steam, and pressure. Temperatures of 140, 160, 180, 200, and 220°C were applied at a maximum steam pressure of 550 kPa and maximum press hydraulic pressure ranging from 4.5 to 9.0 MPa. After densification, the oven-dry density increased significantly, veneers darkened, and lathe checks that were present on veneers before densification were conglutinated and veneer surface roughness decreased. Densified veneers showed markedly reduced hygroscopicity: the higher the densification temperature, the lower the wood hygroscopicity. The Brinell hardness of densified veneer was about two to three times that of control for both aspen and hybrid poplar. Tensile and bending strength also increased significantly after densification. However, the mechanical properties of densified veneers decreased slightly with increased densification temperature. The modulus of elasticity in tension and bending increased after densification, especially at high temperatures. A very high compression set recovery was found for veneers densified at low temperatures. Recovery decreased dramatically when densification temperature exceeded 180°C. Almost no recovery was found for veneers densified at 220°C.
Papa Niokhor Dioufa, Tatjana Stevanovic, Changhua Fang, Alain Cloutier, Pierre Blanchet, Ahmed Koubaa, Nicolas Mariotti. Effects of thermo-hygro-mechanical densification on the surface characteristics of trembling aspen and hybrid poplar wood veneers. 2011. Applied Surface Science 257:3558-3564
DOI : 10.1016/j.apsusc.2010.11.074
The effect of thermo-hygro-mechanical (THM) densification temperature on the surface color, roughness, wettability, and chemical composition of tremblingaspen (Populus tremuloides) and hybridpoplar (Populus maximowiczii × P. balsamifera) veneers was investigated. Veneers were subjected to four THM densification temperatures (160 °C, 180 °C, 200 °C, and 220 °C). Veneer color darkened with increasing THM densification temperature. Surface roughness decreased between 160 °C and 200 °C. Wettability decreased after THM densification, but no significant difference was found between treated specimens. ATR-FTIR and XPS results confirmed that THM densification caused major chemical changes in veneer surfaces, and more pronounced at temperatures higher than 160 °C.
Changhua Fang, Nicolas Mariotti, Pierre Blanchet, Ahmed Koubaa. Densification of wood veneers combined with oil-heat treatment. Part 1 : Dimentional stability. 2010. BioResources 6(1):373-385
Although wood densification by compression improves wood mechanical strength, dimensional stability is often a problem due to compression recovery. Alternatively, oil-heat treatment (OHT) improves wood dimensional stability and enhances resistance to biological attack. This study examined combined wood densification and OHT. Large wood veneer 700 × 700 mm specimens prepared with aspen (Populus tremuloides) were densified using heat, steam, and pressure at 160ºC, 180ºC, and 200°C, respectively. OHT at 180ºC, 200ºC, and 220ºC for 1, 2, and 3h was then applied to the densified veneers. Results show that OHT efficiently improved dimensional stability and reduced compression set recovery. OHT temperature and duration markedly influenced the reduction of compression set recovery: the higher the OHT temperature and duration, the lower the recovery. Less than 5% recovery was obtained under various OHT conditions, and almost 0% recovery under some OHT conditions. Radial and tangential swellings of densified veneers were reduced dramatically. Compared to OHT duration, OHT temperature had a pronounced higher impact on radial and tangential swelling. Irreversible swelling (IS) in the compression direction of densified veneers decreased after OHT, particularly with high temperature and long duration, and anti-swelling efficiency (ASE) in the compression direction improved significantly.
Sébastien Migneault, Fouad Erchiqui, Karl Englund, Michael P. Wolcott, Abdelkader Chaala, Ahmed Koubaa. Application of micromechanical models to tensile properties of wood–plastic composites. 2010. Wood Science and Technology
DOI : 10.1007/s00226-010-0351-5
Wood–plastic composites (WPC) were produced with white birch pulp fibers of different aspect ratios (length-to-diameter), high-density polyethylene, and using two common processes: extrusion or injection molding. Three additive levels were also used: no additive, compatibility agent, and process lubricant. Fiber size was measured with an optical fiber quality analyzer. Tensile properties of WPC were measured and modeled as a function of fiber aspect ratio. Models were fitted to experimental values using the minimum sum of squared error method. A shift from the oriented fiber case (injection molding) to the randomly oriented fiber case (extrusion) was achieved using a fiber orientation factor. Fiber/matrix stress transfer increased with increasing fiber aspect ratio. Stress transfer was reduced with the use of process lubricant. Unexpectedly, the compatibility agent had the same effect. Fiber strength and stiffness contributions to the composite were lower than those of intrinsic fiber properties.
Roger E. Hernandez, Svetka Kuljch, Ahmed Koubaa. Effect of cutting width and cutting height on the surface quality of black spruce cants produced by a chipper-canter. 2010. Wood and Fiber Science 42(3):1-12
The effects of the cutting height and cutting width on the surface quality of black spruce cants produced by a chipper-canter were evaluated. Three diameter classes (101.6, 152.4 and 203.2 mm, as measured at the small end diameter of the log) each processed using two cutting widths (12.5 and 25 mm) were studied. The rotation and feed speeds, kept constant at 783 rpm and 197 m/min, yielded a nominal feed per knife (chip length) of 31.5 mm. Twelve logs for each cutting condition were transformed under frozen and unfrozen wood temperatures (winter and summer). The surface quality was analyzed according to roughness and waviness standard parameters. Torn grain was evaluated by means of its maximum depth. The results showed that the surface quality was affected by cutting height, cutting width, and temperature of logs. In general, surface quality was better when processing unfrozen logs at lower cutting width and cutting height. Surface quality varied also within the cant, being generally better at the small end of the log and at the upper part of the cant. The results give useful information to improve the performance of the chipper-canter in terms of surface quality.
Sébastien Migneault, Hamid Nadji, Bernard Riedl, Tony Zhang, James Deng, Ahmed Koubaa. Medium-density fiberboard produced using pulp and paper sludge from different pulping processes. 2010. Wood and Fiber Science 42(3):1-12
Pulp and paper sludge can be recycled in the manufacture of medium-density fiberboard (MDF) because it contains wood fibers. A comparative study was conducted to evaluate the properties of MDF made from virgin fibers mixed with different pulp and paper sludge sources. A factorial design was used in which factors were mill pulping processes, thermal–mechanical pulping (TMP), chemical–thermal–mechanical pulping (CTMP), and kraft pulping, and percentage of sludge mixed with virgin fibers (0, 25, 50, and 75%). Virgin fibers were obtained from paper birch wood, an underutilized species. Chemical composition, physical characteristics, pH, and buffer capacity of sludge were measured. MDF properties decreased mostly linearly with sludge content. Panel properties negatively correlated with the proportion of nonfibrous material such as ash and extractives. TMP and CTMP sludge sources produced panels of similar quality, and kraft sludge produced the lowest quality. It was concluded that the amount of sludge that can be incorporated into MDF without excessive decrease in panel quality depends on the pulping process. At 25% sludge content, all panels met ANSI quality requirements for MDF used for interior applications.
Patrice Soulonganga, Martin Claude Ngueho Yemele, Alain Cloutier, Michael P. Wolcott, Ahmed Koubaa. Effect of bark fiber content and size on the mechanical properties of bark/HDPE composites. 2010. Composites Part A 41:131–137
DOI : 10.1016/j.compositesa.2009.06.005
Black spruce and trembling aspen bark fibers and high density polyethylene were used to process bark– plastic composites by extrusion. Fibers of fine, medium, and coarse size and contents of 50% and 60% based on oven-dry weight were used. The effects of species, fiber content and size on the flexural and tensile properties of the composite were investigated and were found to be highly significant. Black spruce bark composites exhibited higher strength but showed more brittle behavior than aspen bark composites. The effect of content on mechanical properties was more important than size. Compared to wood flour composites, those from bark showed lower strength.
Hassine Bouafif, Patrick Perré, Alain Cloutier, Ahmed Koubaa. Effects of composite processing methods on wood particle development and length distribution: consequences on mechanical properties of wood–thermoplastic composites. 2010. Wood and Fiber Science 42(1):62-70
The relationship between structure and properties of high-density polyethylene (HDPE) filled with wood particles and processing techniques—injection molding, compression molding, and extrusion— was investigated. Wood particles were hammer-milled, sieved, and compounded into pellets at 35% by weight with HDPE using a twin-screw extruder. Coupling agent (ethylene-maleic anhydride copolymer) was added at 2% by wood filler weight. The pellets were used to produce test samples using the three processing techniques. The sensitivity of jack pine and several other wood particles (eastern white cedar, black spruce, and jack pine bark) to composite processing was analyzed. Bark particles showed higher propensity to generate fines than wood particles, possibly because of a higher thermal sensitivity. The major reduction in mean particle length was found to occur in the compounding process. Extrusion and injection molding contributed to particle length reduction to a lesser extent. Conversely, compression molding did not cause significant damage to wood particles. Stiffness and strength increased linearly with weight-averaged length.
David (Young-In) Park, Ahmed Koubaa, Marc Mazerolle, Suzanne Brais. Effects of Cambial Age and Stem Height on Wood Density and Growth of Jack Pine Grown in Boreal Stands. 2009. Wood and Fiber Science
Jack pine specimens were examined for longitudinal and radial variations in selected wood quality parameters. Wood density and ring width of cross-sections were measured systematically from pith to bark along the merchantable stem using X-ray densitometry. Effects of cambial age and stem height were analyzed using a linear mixed model with two levels of nesting. A strong interaction between the two factors was found in corewood. Tree individual variation increased with cambial age for all studied wood properties and was larger in earlywood than in latewood. Radial patterns in the studied parameters closely approximated published ones in the lower stem but lessened considerably with increasing stem height. By contrast, longitudinal patterns reversed with cambial age in earlywood. High coordination was found between longitudinal patterns in corewood and radial patterns in the stem base, indicating a similar maturation pattern in the apical meristem and cambia. However, with increasing cambial age, this high coordination disappeared rapidly.
Julia Savva, Yves Bergeron, Ahmed Koubaa, Francine Tremblay. Effects of radial growth, tree age, climate, and seed origin on wood density of diverse jack pine populations. 2009. Trees
DOI : 10.1007/s00468-009-0378-0
Several models of the effects of silviculture, radial growth, and tree age on wood density have been developed, but they have rarely considered the roles of diverse seed origins and climate. We developed a model to test the effects of radial growth, tree age, climate, and seed-source origins on wood density in 21 diverse populations of jack pine in a common garden in Petawawa, Ontario, Canada over the last 24 years using a linear mixed-effects model. Although we found significant differences in wood density among diverse seed origins, there were no differences between seed origins having the same ring age and ring width, indicating an indirect effect on wood density of seed-source origin via radial growth. High variation in wood density among trees within the same population and between populations indicated high genetic control of wood density. The climate effect was significant on wood density in all populations, but smaller when radial growth was controlled. Climate effect did not differ significantly among populations. Precipitation in July negatively affected latewood density, whereas precipitation in May in the current year and September of the previous year negatively affected earlywood density. We concluded that a single model of jack pine wood density and radial growth could be used, either controlling for climate effects or not, as the relationship between wood density and radial growth is preserved among the diverse populations, and the climate effect controlling for radial growth in the model was only slight.
Alain Cloutier, Martin Claude Ngueho Yemele, Papa Niokhor Dioufa, Pierre Blanchet, Tatjana Stevanovic, Ahmed Koubaa. Physical and mechanical properties of particleboard made from extracted black spruce and trembling aspen bark. 2008. Forest Prod. J. 58(10):38-46.
Bark residues are mostly used for thermal energy production. However, a better utilization of that resource could be as raw material for particleboard (PB) manufacturing. Bark is also a source of numerous extractives used in several fields including pharmacology and adhesive production. This study aims at analyzing the effect of hot water extracted bark particle content and size on the physical and mechanical properties of bark PBs including the modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), Janka hardness (HJ), thickness swelling (TS) and linear expansion (LE). Moreover, these properties were compared both to a control (100% wood particles) and to PB made from the same content of unextracted bark. The results showed that, while the mechanical properties of the PB made from extracted black spruce and trembling aspen bark decreased with increasing bark content, LE increased. PB made of fine particles often showed higher IB and lower TS values. Hot water extraction of the bark had a detrimental effect on all the physical and mechanical properties of the PBs produced except for the Janka hardness, where no significant decrease was found. TheMOEandMORof the PBs made from 50 percent black spruce and trembling aspen bark met the requirements of the ANSI standard for commercial (M–1) and underlayment (PBU) grades. In contrast, the dimensional properties (TS and LE) of all the boards did not fulfill the minimum requirements of the ANSI standard.
Hassine Bouafif, Patrick Perré, Ahmed Koubaa, Bernard Riedl, Alain Cloutier. Analysis of Among-Species Variability in Wood Fiber Surface Using DRIFTS
and XPS: Effects on Esterification Efficiency. 2008. Journal of Wood Chemistry and Technology. 28: 296–315.
DOI : 10.1080/02773810802485139
Variability in the chemical composition of surface properties of various wood
fibers (eastern white cedar, jack pine, black spruce, and bark) was investigated using
diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and X-ray photoelectron
spectroscopy (XPS). Both DRIFTS and XPS showed high variability in fiber
surface composition between species and between fiber types (sapwood, heartwood,
and bark). Fiber surface was modified by esterification reaction using a maleic anhydride
polyethylene (MAPE) treatment. DRIFTS failed to assess surface modification,
whereas XPS results showed that MAPE treatment increased the surface hydrocarbon
concentration of jack pine wood fiber, indicated by a decrease in oxygen–carbon ratio
and an increase in relative intensity of the C1 component in the C1s signal. Lignin
concentration variability on the fiber surface was determined as the major factor that
prevents esterification from taking place.
Martin Claude Ngueho Yemele, Pierre Blanchet, Alain Cloutier, Ahmed Koubaa. Effects of bark content and particle geometry on the physical and mechanical
properties of particleboard made from black spruce and trembling aspen bark. 2008. Forest Prod. J. 58(11):48–56.
Bark residues are mostly used for thermal energy production. However, a better utilization of that resource could be as raw
material for particleboard manufacturing. The use of bark in wood particleboard manufacturing is currently viewed negatively
due to the fact that an excessive bark content in the furnish produces significant adverse effects on strength properties and
dimensional stability of the boards. Strategies could be found to improve some properties of particleboard made from bark. The
effects of bark particle content and geometry on the physical and mechanical properties of the panels including the modulus of
elasticity (MOE), modulus of rupture (MOR), internal bond (IB), Janka hardness (HJ), thickness swelling (TS), and linear
expansion (LE) were investigated. The best panels in terms of properties were compared to a control made of 100 percent wood
particles. The results showed that, while the mechanical properties of the particleboard made from black spruce and trembling
aspen bark decreased with increasing bark content, LE increased and TS increased slightly. The IB of particleboard made from
50 percent bark content decreased with increasing particle size. Particleboard made from 50 percent black spruce bark showed
the highest MOE, MOR, and IB and the lowest LE with values 12, 37, and 54 percent lower and 45 percent higher than the
control, respectively. The MOE, MOR, IB, and HJ of boards made from 50 percent black spruce and trembling aspen bark met
the requirements of the ANSI A208.1 to 1999 standard. Particleboard made from trembling aspen bark showed the lowest TS.
Wei-dan Ding, Abdelkader Chaala, Tikou Belem, Cornelia Krause, Ahmed Koubaa. Relationship between wood porosity, wood density and methyl methacrylate
impregnation rate. 2008. Wood Material Science and Engineering. 3(1):62-70.
DOI : 10.1080/17480270802607947
Martin Claude Ngueho Yemele, Ahmed Koubaa, Papa Niokhor Dioufa, Pierre Blanchet, Tatjana Stevanovic, Alain Cloutier. Effects of hot water treatment of black spruce and trembling aspen bark raw material on the physical and mechanical properties of bark particleboard. 2008. Wood and Fiber Science 40(3):339-351.
The understanding of the interaction between bark extractives and adhesives is fundamental
in the manufacture of bark particleboard for optimum adhesive curing, and mechanical and physical
properties of the boards. The effect of hot-water treatment on black spruce and trembling aspen bark was
investigated to highlight its impact on the bark particles/phenol-formaldehyde adhesive system, and on the
physical and mechanical properties of bark particleboard made from hot-water-treated bark of both
species. Bark was soaked in hot water maintained at 100°C for 3 h. The results showed that the hot-water
treatment affects the physical and chemical properties of the bark by decreasing hydrophilic characteristics,
acidity, and the amount of condensable polyphenols that can react with formaldehyde. The mechanical
properties, including static bending and internal bond of particleboard made from untreated black
spruce and trembling aspen bark, were higher than those of boards made from hot-water-treated bark of
the same species. The thickness swelling of particleboard made from hot-water-treated black spruce and
trembling aspen bark was higher than that made from untreated bark. One exception occurred for particleboard
made from 100% trembling aspen bark for which no significant difference was found between
particleboards made from treated and untreated barks.
Julia Savva, Ahmed Koubaa, Yves Bergeron, Bernhard Denneler, Francine Tremblay. Effect of interannual climate variations on radial growth of jack pine provenances in Petawawa, Ontario. 2008. Can. J. For. Res. 38(3): 619-630.
DOI : 10.1139/X07-178 10.1139/X07-178
Abstract:
Effect of interannual climate variations on radial growth was compared among jack pine (Pinus banksiana Lamb.) of diverse geographical origins in a 41-year-old common-garden experiment in Petawawa, Ontario. Provenance experiments established from seeds transferred from different parts of a species range (from the northern United States to northern Canada) to the same environment might be considered as a simulation model of climate change and a shift of climate zones. The following questions are addressed: Did the response of growth to interannual climate variations differ among the provenances transferred within the experimental site? What climatic factors affect interannual growth variations of jack pine provenances? Tree-ring chronologies for 16 populations were developed for the period 1970–2004. The best climate predictors of radial growth were precipitation of June and March of the current year and precipitation of December of the previous year. Although, climatic factors affecting growth were similar between the provenances, absolute radial growth was proportional to the growth potential of the provenances. We conclude that variability due to seeds origins is not a significant source of variation for dendroclimatic studies of jack pine. Increased frequency of summer droughts might result in a growth decrease of jack pine © 2008 NRC Canada.
Résumé
Nous avons étudié les relations entre le climat et la croissance radiale annuelle de provenance de pin gris (Pinus banksiana Lamb.) établis depuis 41 ans dans un jardin commun à Petawawa en Ontario. Des tests de descendance établis dans des conditions similaires à partir de graines provenant de différentes parties de l’aire de distribution de l’espèce (depuis le Nord des Etats-unis jusqu’au nord du Canada) simulent des changements climatiques et des transitions entre différentes zones bioclimatiques. Nous avons tentés de répondre aux questions suivantes : Est-ce que la relation entre la croissance radiale interannuelle et le climat varie en fonction des provenances? Quelles sont les facteurs climatiques qui contrôlent la croissance radiale des différentes provenances. Des chronologies de la croissance radiale couvrant la période 1970–2004 ont été développées pour 16 provenances. Les facteurs climatiques les plus corrélés avec la croissance radiale sont les précipitations pour juin et mars de l’année en cours et les précipitations de décembre pour l’année précédente. Bien que les facteurs climatiques contrôlant la croissance sont les mêmes pour toutes les provenances, la croissance absolue variait en fonction du potentiel de croissance de chaque provenance. Nous concluons que la variabilité due à la provenance des graines ne constitue pas une source importante de variation dans la réponse dendroclimatique chez le pin gris. Une augmentation de la fréquence des sécheresses durant la période estivale pourrait entraîner une diminution de la croissance du pin gris © 2008 NRC Canada.
Julia Savva, Yves Bergeron, M.-G. Tjoelker, Bernhard Denneler, Ahmed Koubaa, Francine Tremblay. Seed transfer and climate change effects on radial growth of jack pine
populations in a common garden in Petawawa, Ontario, Canada. 2007. For. Ecol. Manage. 242(2-3):636-647.
DOI : 10.1016/j.foreco.2007.01.073
The effects of seed transfer and climate change on the width and basal area of tree rings were studied in 21 provenances of jack pine (Pinus
banksiana Lamb.) grown in a common-garden plantation in Petawawa, Ontario, Canada. Seed-source origin significantly influenced both mean
tree-ring width and mean annual basal area increment over a 25-year growth period (1975–1999). Temperature and precipitation transfer functions
were developed to predict width and basal area of tree rings of the jack pine populations. The best predictors of growth were the transfer distances
mean annual maximum daily temperature and annual precipitation between the plantation site and the seed origins. Radial growth of the jack pine
populations was mainly related to temperature at seed origin and, to a lesser degree, to precipitation at seed origin. Extension of the transfer
functions to three sets of independent data revealed significant correlations between estimated and predicted mean radial growth characteristics.
Seed sources of jack pine originating from warmer and drier climates than that of the plantation site in Petawawa had slightly higher mean ring
widths and basal areas than the local populations. The application of different climate change scenarios derived from general circulation models
the developed transfer functions indicated that radial growth of jack pine may decline only if significant climate changes occur, which might
happen before the mid 21st century. Both a higher radial growth of southern seed sources and a potential negative effect of a significant temperature
increase and precipitation decrease in future suggest restricting the northward transfer of southern seed sources to less than 18 latitude. However,
provenance specific differences in survivorship, frost- and disease-resistance, and cone serotiny should also be taken into consideration.© 2007 Elsevier B.V. All rights reserved.
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