Zhang Y.,Nanjing Forestry University |
Cai L.,665 East Mall
Drying Technology | Year: 2011
Mills experience reduced kiln productivity in drying sub-alpine fir lumber. High-temperature drying is an effective approach to accelerate the process. Thermal modification improves the dimensional stability and decay resistance. During these processes, two distinct stages, wood heating and water vaporization, were encountered. This research was aimed at developing a method to evaluate the vaporization process using an approximate analytic solution. The heating process was predicted by combining the analytic solution with numeric simulation. Using a scanning electron microscope, the impact of vaporization on wood micro-structure was examined. The vaporization process was able to open the aspirated pits and break the membranes. Laboratory drying experiments confirmed that the program could obtain satisfactory estimations of heating rates and times. The results indicated that the vaporization time is a function of the moisture content and size of the lumber, the temperature and air velocity in the kiln. © 2011 Taylor & Francis Group, LLC.
Han G.,Northeast Forestry University |
Deng J.,FPInnovations Forintek Division |
Zhang S.,665 East Mall |
Bicho P.,800 Wesbrook Mall |
Wu Q.,Louisiana State University
Industrial Crops and Products | Year: 2010
Steam explosion treatments were used to modify straw fiber attributes for panel manufacturing. In particular, the effect of steam temperature and retention time on morphology, acidity, wettability, and ash and silicon contents of wheat straw was studied. After steam explosion treatments, proportion of large particles decreased, while fiber bundles increased. Higher steam temperature and longer retention time resulted in more homogeneous fiber-like material. The results showed that the pH value of the untreated wheat straw fiber was nearly 7 and the pH values and acid buffer capacities of straw were greatly reduced after steam explosion treatments. This indicated that the acidity of straw increased after steam explosion treatments. The dynamic contact angle of the straw before the treatment was nearly 90°, indicating that the straw material without treatment is more hydrophobic. After steam explosion treatments, the contact angle of straw was significantly reduced, showing that the surface wettability of the treated straw was improved. The ash and silicon contents of straw were also significantly reduced by steam explosion treatments. The improved acidity and wettabillity as well as decreased silicon content would contribute to the improved bondability between straw particles and water-soluble adhesive binders. © 2009 Elsevier B.V. All rights reserved.
Migneault S.,Laval University |
Koubaa A.,University of Québec |
Nadji H.,Laval University |
Deng J.,19 rue Franquet |
Zhang S.Y.,665 East Mall
Wood and Fiber Science | Year: 2011
Pulp and paper sludge is valuable in fiberboard manufacturing because primary sludge (PS) contains fibers and secondary sludge (SS) has adhesive properties. We evaluated properties of binderless fiberboard made from conventional pulp and paper mill sludge sources using a factorial design in which the factors were SS:PS ratio (1:9, 2:8, and 3:7) and pulping process (thermomechanical [TMP], chemical- thermomechanical [CTMP], and kraft). Sludge was collected, refined, dried, and characterized for chemical composition and fiber length. Internal bond strength of CTMP panels increased 90% and thicknessswell of TMP panels improved 92% with increasing SS content from 10-30%. IR Fourier transform and X-ray photoelectron spectroscopy analyses were conducted to better understand these results. Increased bonding was attributed to presence of proteins and lignin on the sludge fiber surface, which enhanced adhesion during hot pressing, whereas surface contamination decreased bonding efficiency. The TMP formulation at SS:PS ratio 3:7 met the ANSI requirement for basic hardboard. All other formulations were not dimensionally stable enough to meet the standard. The CTMP source resulted in the highest mechanical properties, and thickness swell was similar for the TMP and CTMP pulping processes. The kraft source produced low-integrity and dimensionally unstable panels. © 2011 by the Society of Wood Science and Technology.
Schneider R.,University of Quebec at Rimouski |
Berninger F.,University of Quebec at Montréal |
Ung C.-H.,Natural Resources Canada |
Makela A.,University of Helsinki |
And 2 more authors.
Tree Physiology | Year: 2011
The relationship between sapwood area and foliage biomass is the basis for a lot of research on eco-phyisology. In this paper, foliage biomass change between two consecutive whorls is studied, using different variations in the pipe model theory. Linear and non-linear mixed-effect models relating foliage differences to sapwood area increments were tested to take into account whorl location, with the best fit statistics supporting the non-linear formulation. The estimated value of the exponent is 0.5130, which is significantly different from 1, the expected value given by the pipe model theory. When applied to crown stem sapwood taper, the model indicates that foliage biomass distribution influences the foliage biomass to sapwood area at crown base ratio. This result is interpreted as being the consequence of differences in the turnover rates of sapwood and foliage. More importantly, the model explains previously reported trends in jack pine sapwood area at crown base to tree foliage biomass ratio. © The Author 2011. Published by Oxford University Press. All rights reserved.
Janin A.,University of Toronto |
Coudert L.,University of Québec |
Blais J.-F.,University of Québec |
Mercier G.,University of Québec |
And 3 more authors.
Separation and Purification Technology | Year: 2012
Increasingly stringent regulations regarding waste disposal encourage the development of options for reuse, recycling and revalorisation of waste. Metals-bearing treated wood wastes are no exception. Previous studies identified a possible treatment technology for chromated copper arsenate (CCA) preservative-treated wood waste based on sulphuric acid leaching. In this study, the scale-up of this technology was extended from 200 ml flask to 80 l working volume stirred-tank reactor. The study involved three leaching steps of 2 h each, at 75 °C with 0.2 N H 2SO 4 and 15% solids content followed by three rinsing steps. This procedure led to removal of 99.5% of the arsenic, 95.7% of the chromium and 99.6% of the copper from the wood chips on average. The effluents generated by the leaching steps were then treated by precipitation. This technology allowed 99% removal of As, Cr and Cu from the leachate, leading to effluents satisfying the regulations for effluent discharge in municipal sewers. The mass balance was assessed for the whole process (leaching, rinsing and precipitation of the leachate) and the output to input ratio was between 80% and 100%. Furthermore, the economic analysis concluded that the operating cost of the process (leaching, rinsing and precipitation of the leachate) was about 250 $/ton of treated wood (t.t.w.) with the conditions employed in this study. However, the cost could be reduced at least to 89 $/t.t.w. by using a counter current leaching process as developed in a previous study. © 2011 Elsevier B.V. All rights reserved.
Zhao Y.,University of Toronto |
Yan N.,University of Toronto |
Feng M.W.,665 East Mall
ACS Sustainable Chemistry and Engineering | Year: 2013
In this study, two types of biobased bark-derived phenol formaldehyde (PF) resins, namely, liquefied bark-PF and bark extractive-PF, were synthesized from acid-catalyzed phenol-liquefied bark and bark alkaline extractives, respectively. The biobased resins were characterized for their chemical compositions and molecular structures using the liquidstate 13C nuclear magnetic resonance (NMR) technique. The results indicated that the introduction of bark components (either as liquefied bark or as bark extractives) to the phenolic resin synthesis affected resin structures and curing performance. Methylene ether bridges were found in the bark-derived PF resins. Bark components made the formation of para-ortho-methylene linkage more favorable in bark-derived PF resins than in lab PF resins. Molecular structures of the liquefied bark-PF resin differed significantly from those of the bark extractive-PF resins. The liquefied bark-PF resin showed a higher ratio of para-para/ortho-para-methylene link (-CH2-), a higher unsubstituted/substituted hydrogen (-H/-CH2OH) ratio and a higher methylol/methylene (-CH2OH/-CH2-) ratio than the bark extractive-PF resin. The tannin components of the bark extractives accelerated the curing rate of the resulting bark extractive-PF resin. The bark extractives made the ortho position of phenol react more favorably with formaldehyde than the para position. The liquefied bark with phenolated structures had more reactive sites toward formaldehyde than the bark extractives and accelerated the curing rate of the resulting liquefied bark-PF resin. © 2012 American Chemical Society.
Zhao Y.,University of Toronto |
Yan N.,University of Toronto |
Feng M.,665 East Mall
International Journal of Adhesion and Adhesives | Year: 2010
In this study, lodgepole pine (Pinus contorta Dougl.) barks with and without infestation by mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins) were liquefied in phenol with sulfuric acid. The liquefied portions of the bark were used to synthesize bark-derived phenolformaldehyde (BPF) adhesive resins under alkaline conditions. In comparison to a commercial phenolformaldehyde (PF) resin and a lab PF resin, the BPF resins were found to have larger average molecular weights, higher polydispersity indices and shorter gel times. The viscosities of the BPF resins were higher than the viscosity of the lab PF resin but lower than the viscosity of the commercial PF resin. Isothermal DSC tests indicated that all resins exhibited both nth-order and autocatalytic cure mechanisms. The post-curing thermal stability of the BPF resins was similar to that of the lab PF resin at higher temperatures but differed significantly from that of the commercial PF resin. All these resins had similar dry bonding strengths; the BPF resins showed the highest wet bonding strengths. Beetle infestation was shown to have no negative effect on the bonding properties of the BPF resins. © 2010 Elsevier Ltd.
Zhou C.,University of British Columbia |
Dai C.,665 East Mall |
Smith G.D.,University of British Columbia
Holzforschung | Year: 2010
To improve the fundamental understanding of wood composite consolidation, the viscoelastic behavior of aspen wood strands is experimentally investigated for a range of temperatures (20-200°C) and moisture contents (0-15%). The results show that the strand stress relaxation modulus and time follows a linear relationship in a log-log plot. The strand stress relaxation rate is highly dependent on the imposed strain levels and the environmental conditions. A model for predicting the stress relaxation of wood strands is developed and compared with the experimental results. It will be useful to further predict the stress relaxation response of strand-based wood composite mats during hot pressing. © 2010 by Walter de Gruyter Berlin New York 2010.
Cai L.,665 East Mall |
Oliveira L.C.,665 East Mall
Wood Science and Technology | Year: 2010
Sub-alpine fir is characterized by its high proportion of wet pockets making it difficult to dry. Since it takes longer to dry, mills experience reduced kiln productivity and increased energy consumption. High temperature drying (HTD) can be an effective approach to accelerate the drying process. In this study, three drying schedules, namely, conservative (control), HTD, and HTD and conservative combined (HTD/Cons), were evaluated when drying green sub-alpine fir 200 9 400 dimension lumber. The results indicated that: (1) the drying rates in the HTD and HTD/Cons schedules were increased by 31-150% in comparison to the drying rates obtained for the conservative schedule; (2) although drying stresses observed for the HTD schedule were higher than those that were measured for the conservative schedule, no significant difference in drying stresses was found between the HTD/ Cons and conservative schedules; (3) warp was reduced in both HTD and HTD/ Cons schedules; (4) neither the HTD nor HTD/Cons schedule showed any significant reduction in modulus of rupture (MOR) and modulus of elasticity (MOE) when compared to the values obtained for the conservative schedule. Diffusion coefficients during HTD for sub-alpine fir were determined and it was found that diffusivity increases with temperature. A mathematical model describing the processes of heating and drying under high temperatures was developed. The results of drying tests showed that the predicted drying curves by the model satisfactorily agree with the experimental data. © Springer-Verlag 2009.
Oliveira L.C.,665 East Mall
Wood and Fiber Science | Year: 2010
This study was undertaken to determine the heating process of frozen lodgepole pine (Pinus contorta) lumber because many regions in Canada have to heat-treat or dry frozen lumber in the winter. Because phytosanitary regulations require that lumber products be heat-treated before delivery to customers (core wood temperature of 56°C for 30 min), it is important to determine the time required to reach this criterion. In this study, 10 heating runs were made with different initial moisture contents (MCs) and temperatures using a laboratory kiln humidified with low-pressure steam or cold water spray. To simulate the performance of frozen lumber, the existing heating model for unfrozen lumber was modified by adding a phase-change analysis and was verified using the data from laboratory experiments. The experimental results combined with the model predictions indicated that the thawing time was increased for frozen lumber with higher initialMC. The modified model satisfactorily estimates heating times for frozen lodgepole pine lumber. © 2010 by the Society of Wood Science and Technology.