| 1. |
- Sjökvist, Tinh, Teknisk doktor, 1978-, et al.
(author)
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Liquid water absorption in coated Norway spruce : Impact of heartwood, sapwood, density and weather exposure
- 2020
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In: MADERAS. - : Universidad del Bio-Bio. - 0717-3644 .- 0718-221X. ; 22:3, s. 335-346
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Journal article (peer-reviewed)abstract
- Water is one of the most significant factors for the durability of wood. A common solution is to use a coating to protect and maintain low water content. However, little knowledge exists how the underlying wood substrate affects the water sorption of coated wood. Therefore, the liquid water absorption of coated and uncoated Norway spruce heartwood and sapwood with a variety of densities was measured by letting the panels float freely in the water. The effect of one year weathering of the coatings was also included. Coated heartwood and sapwood had no difference in water absorption in opposite to uncoated spruce. The influence of heartwood and sapwood seemed to have limited impact when a coating hindered the presence of free water. Wood density had a positive effect on the absorption of coated wood, i.e. low absorption for low-density samples, in opposite to uncoated samples. Low-density characteristic also contributed to a lower increase of water absorption after weather degradation, for samples with water-borne coatings. Natural weathering enhanced the effect of wood characteristics on coated samples, likely by an increase of coating permeability.
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| 2. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(author)
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Anatomical, Physical, Chemical, and Biological Durability Properties of Two Rattan Species of Different Diameter Classes
- 2022
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In: Forests. - Switzerland : MDPI. - 1999-4907. ; 13:1
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Journal article (peer-reviewed)abstract
- Rattan cane is an important forest product with economic value. Its anatomical, physical, and biological properties vary with the cane height. This makes it difficult to select the appropriate cane diameter for harvesting. Understanding the material properties of rattan cane with different diameter sizes is important to enhance its utilization and performance for different end uses. Thus, the present study was performed on two rattan species, Calamus zollingeri and Calamus ornatus, at two different cane heights (bottom/mature and top/juvenile). Calamus zollingeri was studied at diameter classes of 20 mm and 30 mm, while Calamus ornatus was analyzed at a diameter class of 15 mm. The anatomical properties, basic density, volumetric swelling, dynamic moisture sorption, and biological durability of rattan samples were studied. The results showed that C. zollingeri with a 20 mm diameter exhibited the highest basic density, hydrophobicity, dimensional stability, and durability against mold and white-rot (Trametes versicolor) fungi. As confirmed by anatomical studies, this could be due to the higher vascular bundle frequency and longer thick-walled fibers that led to a denser structure than in the other categories. In addition, the lignin content might have a positive effect on the mass loss of different rattan canes caused by white-rot decay.
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| 3. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(author)
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Micro-Fibrillated Cellulose in Lignin–Phenol–Formaldehyde Adhesives for Plywood Production
- 2023
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In: Forests. - Switzerland : MDPI. - 1999-4907. ; 14:11
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Journal article (peer-reviewed)abstract
- Petrochemical-based phenol–formaldehyde (PF) adhesives are widely used in plywood production. To substitute phenol in the synthesis of PF adhesives, lignin can be added due to its structural similarity to phenol. Moreover, micro-fibrillated cellulose (MFC) can further enhance the bond performance, mechanical properties, and toughness of adhesive systems. Thus, the aim of this study was to evaluate the adhesion performance of lignin–PF (LPF) adhesives reinforced with MFC. In LPF formulations, three levels of MFC (0, 15, and 30 wt% based on the total solid content of adhesives) were added to the homogenous adhesive mixture. Three-layer plywood panels from birch (Betula pendula Roth.) veneers were assembled after hot pressing at 130 °C under two pressing durations, e.g., 60 and 75 s/mm. Tensile shear strength was measured at dry (20 °C and 65% RH) and wet conditions (water soaked at room temperature for 24 h). The results indicated that the addition of lignin reduced the strength of LPF adhesives in both dry and wet conditions compared to the control PF adhesive. However, MFC reinforcement enhanced the shear strength properties of the plywood. Furthermore, a longer pressing time of 75 s/mm slightly increased the shear strength.
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| 4. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(author)
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Prediction of mechanical performance of acetylated MDF at different humid conditions
- 2020
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In: Applied Sciences. - Switzerland : MDPI. - 2076-3417. ; 10:23, s. 1-16
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Journal article (peer-reviewed)abstract
- Change of relative humidity (RH) in surrounding environment can greatly affect the physical and mechanical properties of wood-based panels. Commercially produced acetylated medium density fiberboard (MDF), Medite Tricoya®, was used in this study to predict strength and stiffness under varying humid conditions by separating samples in parallel (//) and perpendicular (⊥) to the sanding directions. Thickness swelling, static moduli of elasticity (MOEstat) and rupture (MORstat), and internal bond (IB) strength were measured at three different humid conditions, i.e., dry (35% RH), standard (65% RH) and wet (85% RH). Internal bond (IB) strength was also measured after accelerated aging test. A resonance method was used to determine dynamic modulus of elasticity (MOEdyn) at the aforementioned humid conditions. Linear regression and finite element (FE) analyses were used to predict the MDF’s static bending behavior. Results showed that dimensional stability, MOEstat, MORstat and IB strength decreased significantly with an increase in RH. No reduction of IB strength was observed after 426 h of accelerated aging test. A multiple regression model was established using MOEdyn and RH values to predict MOEstat and MORstat. In both directions (// and ⊥), highly significant relationships were observed. The predicted and the measured values of MOEstat and MORstat were satisfactorily related to each other, which indicated that the developed model can be effectively used for evaluating the strength and stiffness of Medite Tricoya® MDF samples at any humid condition. Percent errors of two different simulation techniques (standard and extended FE method) showed highly efficient way of simulating the MDF structures with low fidelity.
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| 5. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(author)
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Resonance and time-of-flight methods for evaluating the modulus of elasticity of particleboards at different humid conditions
- 2020
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In: Wood research. - Slovakia : Slovak Forest Products Research Institute. - 1336-4561. ; 65:3, s. 365-380
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Journal article (peer-reviewed)abstract
- Non-destructive testing of wood panels by either resonance or time-of-flight (TOF) methods provides possibilities for predicting their static bending properties. In the present study, three non-destructive devices (BING - Beam Identification by Non-destructive Grading by CIRAD, Montpellier, France, Fakopp Ultrasonic Timer and Sylvatest TRIO) were used for measuring the dynamic stiffness of different particleboard types. Fakopp Ultrasonic Timer and Sylvatest TRIO produce ultrasonic pulses to measure the sound velocity while BING uses resonance frequencies. Commercially produced particleboards with different thickness and densities were used to measure the dynamic modulus of elasticity (MOEdyn) in two directions (parallel and perpendicular to the production line) and at three different humidity levels (dry - 35%, standard - 65% and wet - 85% RH in constant temperature of 20°C ). MOEdyn of particleboards were correlated with the static moduli of elasticity (MOEstat) and rupture (MORstat). It was found that the non-destructive methods gave higher MOEdyn values in both production directions than that of MOEstat values. MOEdyn was found to decrease from dry to wet conditions. A very strong and statistically significant correlation existed between MOEdyn and static bending properties. MOEdyn correlated stronger to MOEstat than MORstat. At different humidity level, all three methods- Fakopp Ultrasonic Timer, BING and Sylvatest TRIO analyses showed good predicting capabilities to estimate MOEstat and MORstat of different particleboard types with high level of accuracy.
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| 6. |
- Bobadilha, Gabrielly S., et al.
(author)
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Effect of exterior wood coatings on the durability of cross-laminated timber against mold and decay fungi
- 2020
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In: BioResources. - USA : North Carolina State University. - 1930-2126. ; 15:4, s. 8420-8433
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Journal article (peer-reviewed)abstract
- Cross-laminated timber (CLT) is increasingly used in building construction worldwide. Durability of CLT against fungal attack has yet to be fully explored. Water intrusion in mass timber can yield dimensional changes and microbial growth. This study evaluated the performance of CLT coated with various water- and solvent-based stains commercially available in the United States. Twelve coatings were tested for moisture excluding effectiveness, water repellency effectiveness, volumetric swelling, and anti-swelling efficiency. Only five coatings repelled water, limiting dimensional changes. A modified version of AWPA E10-16 (2016) was performed to evaluate decay of the coated CLT samples. Weight losses were recorded after 18 weeks' exposure to the brown-rot decay fungus Gloeophyllum trabeum. In accelerated mold testing, coated CLT samples were grown in chambers containing spores of Aspergillus sp., Rhizopus sp., and Penicillium sp. for 29 d and assessed visually for mold growth. In both tests, coating C (transparent, water-based, alkyd/acrylic resin) performed the best among the tested coatings. Mold growth was completely prevented, and weight loss caused by G. trabeum was approximately 1.33%. Although coating C prevented decay for 18 weeks, coatings are not intended to protect against decay fungi. However, they may offer short-term protection during transport, storage, and construction.
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| 7. |
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Dimensional stability of Scots Pine Sapwood Modified by Tannin-based Formulas
- 2024
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Editorial proceedings (peer-reviewed)abstract
- Tannins are polyphenolic compounds extracted from various tree species and used in variousmapplications such as adhesives, composites, pharmaceuticals, medicines, and food and beverage production (Mubarak et al. 2023). However, tannins, especially condensed tannins, have limited reactivity with wood. Consequently, to effectively modify wood, cross-linkers and other reactive chemicals or additives must be used. In this work, we have introduced a bio-based cross-linker in a 20% tannin (Quebracho) aqueous solution. Five levels of cross-linker (0, 2, 10, 20 and 40% of total tannin solid) were used to modify Scotspine (Pinus sylvestris L.) sapwood with dimensions of 25 × 25 × 10 mm3 (radial × tangential × longitudinal). Full-cell impregnation was applied with a 60 min vacuum and pressure for 60 min. Samples were kept at room condition for 24 h, stepwise dried to avoid drying defects and cured at 140 °C for 10 h. Modified wood samples are shown in Figure 1. Weight percentage gain (WPG) and bulking coefficient (BC) after water leaching for 5 days were measured according to Donath et al. (2004).
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| 8. |
- Jiang, Wen, 1990-
(author)
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Acid-catalyzed Liquefaction of Industrial Side-streams for Producing Wood Adhesives and Particleboard
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Big quantities of residues and side-streams are generated annually from forest-based and agricultural industries all around the world and present a relatively unexplored renewable resource. Due to the absence of a regularly updated and systematic database of supply, industrial residues and side-streams usually end up in landfill disposal, are used for energy generation, or remain at the production sites. These renewable side-streams are mainly lignocellulosic materials that can be used for fuels, chemicals, and other value-added materials. However, the difficulty in recovering useful components from industrial wastes from a techno-economic point of view is hindering the use of these materials. There are different methods for converting biomass into fuels, chemicals, and materials, including thermochemical, biochemical, and physical conversion. Negative environmental impacts from direct incineration of waste materials and increasing interest in reducing the dependency on fossil-based sources have increased the need for the valorization of the industrial side-streams for material and chemical applications. Among the different thermochemical conversion methods, liquefaction of lignocellulosic materials is an efficient way to convert solid biomass into liquids. Liquefaction including hydrothermal liquefaction (HTL) and moderate acid-catalyzed liquefaction (MACL), is often carried out in an aqueous environment by employing organic solvents with or without catalyst under pressure or ambient conditions. A liquefaction process is influenced by many factors such as material type, solvent, catalyst, time, and temperature. All the parameters of the liquefaction are related to each other, and they affect the yields and the properties of the final products. Studies on the utilization of industrial waste and side-streams as feedstock for liquefaction have increased in recent years, generating significant interest from both academia and industry. This PhD study included a literature review on liquefaction technologies that provide liquefied products for wood adhesives, followed by experimental work on MACL and its optimization for different industrial side-streams, such as wood sawdust, bark, and oat husks. Liquefaction of those materials led to different liquefaction yields (LY) due to their different chemical compositions. When the same liquefaction conditions were applied, liquefied wood sawdust had the highest LY while liquefied bark had the lowest. This was mainly attributed to wood sawdust having a higher cellulose and lower lignin content, when compared to bark and oat husks. After optimizing the liquefaction of wood sawdust, obtained products were applied in wood adhesive formulations successfully. Crude liquefied wood (CLW) and purified liquefied wood (PLW) polyols were obtained from the liquefaction of wood sawdust with the highest LY of 99.7% and used for the synthesis of polyurethane (PU) adhesives by reacting them with polymeric diphenylmethane diisocyanate (pMDI). The bonding strength and penetration to wood adherends of the PU adhesives were affected by the molar ratios between the isocyanate groups (NCO) in pMDI and the hydroxyl groups (OH) in the CLW and PLW. The highest bonding strength of PU adhesives was achieved at an NCO:OH molar ratio of 1.5:1. The thermal stability of the PU adhesives was improved by increasing the NCO:OH molar ratio. PU adhesives based on CLW and PLW with the same adhesive formulation did not show significant differences in their properties while CLW polyol contained more water and alcohols than PLW. A novel method called partial liquefaction of lignocellulosic biomass was also proposed. Partially liquefied bark (PLB) was prepared and used to replace wood particles for producing particleboards (PB) with or without the presence of a commercial synthetic adhesive, i.e. melamine-urea-formaldehyde (MUF). PLB was shown to provide single-layer PBs with good adhesion, mechanical strength, and water repellency. The overall mechanical properties of non-MUF single-layer PBs were inferior to those of MUF-bonded PBs. Increasing the PLB content up to 9.5% led to enhanced mechanical properties for MUF-bonded PBs. PLB prepared from bark with a particle size less than 2 mm ensured good mechanical behavior of single-layer PBs. Moreover, three-layer particleboards prepared from PLB and wood particles had comparable mechanical properties to the reference PBs made solely from wood particles, and PLB had less influence on the mechanical properties of the PBs when used in the surface layer than in the core layer. Formaldehyde emissions from the three-layer PBs were below the limits required by European Standard EN 13986:2004 and major volatile organic compounds (VOCs) were carboxylic acids. This research provided a comprehensive understanding of converting different lignocellulosic materials by a MACL process into valuable polymers and raw materials, which are suitable for the synthesis of wood adhesives and for the manufacturing of particleboards. Due to time constraints related to conducting the PhD, it was not possible to conduct a full characterization of the liquefied products from the selected materials. Such studies should be part of future research in order to supplement our knowledge of MACL mechanisms.
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| 9. |
- Jiang, Wen, 1990-, et al.
(author)
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Preparation of Polyurethane Adhesives from Crude and Purified Liquefied Wood Sawdust
- 2021
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In: Polymers. - Basel, Switzerland : MDPI. - 2073-4360. ; 13
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Journal article (peer-reviewed)abstract
- Polyurethane (PU) adhesives were prepared with bio-polyols obtained via acid-catalyzedpolyhydric alcohol liquefaction of wood sawdust and polymeric diphenylmethane diisocyanate(pMDI). Two polyols, i.e., crude and purified liquefied wood (CLW and PLW), were obtained fromthe liquefaction process with a high yield of 99.7%. PU adhesives, namely CLWPU and PLWPU,were then prepared by reaction of CLW or PLW with pMDI at various isocyanate to hydroxyl group(NCO:OH) molar ratios of 0.5:1, 1:1, 1.5:1, and 2:1. The chemical structure and thermal behavior of thebio-polyols and the cured PU adhesives were analyzed by Fourier transform infrared spectroscopy(FTIR) and thermogravimetric analysis (TGA). Performance of the adhesives was evaluated by singlelap joint shear tests according to EN 302-1:2003, and by adhesive penetration. The highest shearstrength was found at the NCO:OH molar ratio of 1.5:1 as 4.82 ± 1.01 N/mm2 and 4.80 ± 0.49 N/mm2 for CLWPU and PLWPU, respectively. The chemical structure and thermal properties of the cured CLWPU and PLWPU adhesives were considerably influenced by the NCO:OH molar ratio.
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| 10. |
- Jones, Grace
(author)
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Birch Stem and Wood Traits in Genetic and Silviculture Trials in Southern Sweden
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Swedish tree species of birch (silver: Betula pendula and downy: B. pubescens) are often neglected during forest management activities, resulting in low value logs. This thesis investigated birch stem characteristics and wood properties important for solid wood products, in genetics and management trials in southern Sweden. As well as visual stem size and form measurements, non-destructive testing and evaluation (NDT) tools were used to indirectly estimate wood density (hardness), wood stiffness, and grain angle.The results of this work suggest that for the 19-year-old silver birch and 15-year-old downy birch sites, important solid wood traits were under a reasonable degree of genetic control. It seems possible to breed birch to improve grain angle since heritability and genetic variation was high for this trait. Silver birch genotypes are expected to perform similarly across sites. At a site with both birch species, silver birch was larger with denser wood than downy birch. Few genetic correlations between measurements means selection for one trait will not inadvertently affect another trait. The radial density profiles showed density was continuing to increase. Acoustic velocity (AV) and fibre length were highly correlated, hardness and density were related, and ring width was related to ring density. In a 35-year-old planted Norway spruce stand, naturally regenerated birch AV was not different between treatments (20% or 50% of plot trees were birch by number). However, a correlation was observed between DBH and AV. This older site may reflect common Swedish conditions since planting birch is rare, and likely had more mature birch wood than the genetics trials. Although meeting an immediate need for studies of birch wood properties from managed stands, this work covered few sites. To meet this limitation the tools and techniques applied in this thesis could be used in further studies. The results of this thesis work will be of interest to forest managers who want to breed birch, or select birch stands, for solid wood products.
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