| 1. |
- Taghiyari, Hamid Reza, et al.
(författare)
-
Nanotechnology for wood quality improvement and protection
- 2020
-
Ingår i: Nanomaterials for Agriculture and Forestry Applications. - : Elsevier. - 9780128178522 - 9780128178539 ; , s. 469-489
-
Bokkapitel (refereegranskat)abstract
- Wood is a natural renewable material with unique properties helping mankind to build and develop its communities since the genesis of human on the Earth. Moreover, wood/cellulosic composites provide the opportunity to utilize low-density wood species and agricultural materials that are basically not suitable for structural applications. Although wood is considered irreplaceable, it has some disadvantages narrowing its applications and limiting its service life. These disadvantages mainly include its susceptibility to water and water vapor, biological deteriorating fungi, insects, termites, and marine borers. The present chapter tries to summarize some main areas in which nanotechnology is being used to improve wood and lignocellulosic-based composite panels. Moreover, some new applications and capabilities of this precious natural material are also brought into perspective, areas such as transparent wood, self-cleaning coatings, and smart windows. Though some areas have been thoroughly studied, much potential still exists for further studies and commercialization.
|
|
| 2. |
- Taghiyari, Hamid Reza, et al.
(författare)
-
Shear strength of heat-treated solid wood bonded with polyvinyl-acetate reinforced by nanowollastonite
- 2020
-
Ingår i: Wood research. - : Slovak Forest Products Research Institute. - 1336-4561. ; 65:2, s. 183-194
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigated the shear strength of heat-treated solid wood of three species (beech, poplar, and fir) bonded with polyvinyl-acetate (PVA) adhesive reinforced by nanowollastonite (NW). Wood specimens were heat-treated at 165°C and 185°C, and then bonded using PVA reinforced by 5% and 10% of NW. Shear strength tests parallel to the grain of bonded specimens were performed according to ASTM D143-14 (2014). The results demonstrated that the shear strength was significantly dependent upon the density of the specimens. Heat treatment decreased the shear strength of the bonded specimens considerably. This was attributed to several factors, such as a reduction in polar groups in the cell wall, increased stiffness of the cell wall after heat treatment, and a reduction in the wettability of treated wood. However, NW acted as a reinforcement agent or extender in the complex, and eventually improved the shear bond strength. Moreover, the density functional theory (DFT) proved the bond formation between calcium atoms in the NW and hydroxyl groups of cell wall polymers. The overall results indicated the potential of NW to improve the bonding strength of heat-treated wood.
|
|
| 3. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(författare)
-
Anatomical, Physical, Chemical, and Biological Durability Properties of Two Rattan Species of Different Diameter Classes
- 2022
-
Ingår i: Forests. - Switzerland : MDPI. - 1999-4907. ; 13:1
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 4. |
- Ahmed, Sheikh Ali, Senior Lecturer, 1977-, et al.
(författare)
-
Micro-Fibrillated Cellulose in Lignin–Phenol–Formaldehyde Adhesives for Plywood Production
- 2023
-
Ingår i: Forests. - Switzerland : MDPI. - 1999-4907. ; 14:11
-
Tidskriftsartikel (refereegranskat)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.
|
|
| 5. |
- Anuar Bahari, Shahril, et al.
(författare)
-
Strength Performance and Microstructure Characteristic of Naturally-Bonded Fiberboard Composite from Malaysian Bamboo (Bambusa vulgaris)
- 2022
-
Ingår i: Journal of Renewable Materials. - : Tech Science Press. - 2164-6325 .- 2164-6341. ; 10:10, s. 2581-2591
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigated the mechanical properties and microstructural characteristics of fiberboard composite produced by naturally-bonded Malaysian bamboo fiber (Bambusa vulgaris). The components that obtained through soda pulping of bamboo culms such as fiber and black liquor, were used for the preparation of high-density fibreboard composite at two target densities of 850 and 950 kg/m3. The bamboo fiberboard composite (BFC) were then produced at 200°C and two pressing parameters of 125 and 175 s/mm. The mechanical properties, e.g., flexural strength and internal bonding (IB) of BFC samples were evaluated according to BS EN 310: 1993 and BS EN 319: 1993, respectively. It was found that the mechanical performance of the composite with 850 kg/m3 density was significantly higher than 950 kg/m3 ones, especially for the samples with 125 s/mm pressing parameter. Microstructure characteristic of the BFC samples illustrated that the fiber linkages were cracked in the composites with higher density, e.g., the composite with the density of 950 kg/m3 and also black liquor were slightly degraded at longer pressing time, which led to the reduction in mechanical properties, especially in IB strength.
|
|
| 6. |
- Bari, Ehsan, et al.
(författare)
-
Failure characteristics of thermally modified poplar wood subjected to mechanical tests
- 2023
-
Ingår i: IRG documents database and compendium. - : International Research Group of Wood Protection.
-
Konferensbidrag (refereegranskat)abstract
- Poplar (Populus spp.) are among the fastest growing timber species and have been widely planted for use in plywood, composites, pallets, furniture components and paper production. However, the low density of the wood limits many structural applications and the wood has little resistance to biodegradation. Thermal modification represents one approach to improving durability by changing the moisture behavior of the wood, but it can also have adverse effects on structural performance. Understanding the potential effects of thermal treatment on poplar properties can help define the most appropriate applications for these materials. Poplar timbers from Iran were subjected to 30 or 60 min of thermal treatment at temperatures ranging from 110 to 220 °C. Samples were then evaluated for mass loss during treatment, changes in flexural properties, e.g., modulus of elasticity (MOE) and modulus of rupture (MOR), the degree of polymerization, and water absorption characteristics. MOR of controls subjected to 100 °C were similar to those exposed to 160 °C, while MOE was more variable with a slight upward trend for samples exposed to a given heating regime for only 30 min. The increases in MOE may be related to changes in cellulose crystallinity. Mass losses increased with increasing temperature exposure while moisture absorption decreased as expected with longer thermal exposure. The degree of polymerization remained similar for samples exposed up to 170 °C and then increased at higher temperatures. The increases may reflect the complete destruction of shorter chain polymers, leaving only the heat-resistant longer chain polymers. The results suggest that poplar can be thermally modified within limited parameters to improve some performance attributes without adversely affecting its structural capacity.
|
|
| 7. |
- Bari, Ehsan, et al.
(författare)
-
Fungal behavior and recent developments in biopulping technology
- 2024
-
Ingår i: World Journal of Microbiology & Biotechnology. - : Springer Nature. - 0959-3993 .- 1573-0972. ; 40:7
-
Tidskriftsartikel (refereegranskat)abstract
- Biological pretreatment of wood chips by fungi is a well-known approach prior to mechanical- or chemical pulp production. For this biological approach, a limited number of white-rot fungi with an ability to colonize and selectively degrade lignin are used to pretreat wood chips allowing the remaining cellulose to be processed for further applications. Biopulping is an environmentally friendly technology that can reduce the energy consumption of traditional pulping processes. Fungal pretreatment also reduces the pitch content in the wood chips and improves the pulp quality in terms of brightness, strength, and bleachability. The bleached biopulps are easier to refine compared to pulps produced by conventional methodology. In the last decades, biopulping has been scaled up with pilot trials towards industrial level, with optimization of several intermediate steps and improvement of economic feasibility. Nevertheless, fundamental knowledge on the biochemical mechanisms involved in biopulping is still lacking. Overall, biopulping technology has advanced rapidly during recent decades and pilot mill trials have been implemented. The use of fungi as pretreatment for pulp production is in line with modern circular economy strategies and can be implemented in existing production plants. In this review, we discuss some recent advances in biopulping technology, which can improve mechanical-, chemical-, and organosolv pulping processes along with their mechanisms.
|
|
| 8. |
-
Dimensional stability of Scots Pine Sapwood Modified by Tannin-based Formulas
- 2024
-
Proceedings (redaktörskap) (refereegranskat)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).
|
|
| 9. |
- García-Iruela, Alberto, et al.
(författare)
-
Effect of Degradation on Wood Hygroscopicity : The Case of a 400-Year-Old Coffin
- 2020
-
Ingår i: Forests. - : MDPI. - 1999-4907. ; 11:7, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- The hygroscopicity and thermodynamic properties of Pinus sylvestris L. wood from a coffin allegedly holding the remains of famous Spanish author Miguel de Cervantes Saavedra (1547–1616) were studied using the 15 °C and 35 °C isotherms fitted to the Guggenheim–Anderson–de Boer model and comparing them with the isotherms of recently felled wood of the same species. In addition, using infrared spectroscopy (FTIR-ATR) and X-ray diffractograms, the functional groups were determined and the crystallinity and organization of the cell wall components were analyzed. The absence of the 1740 cm−1 group indicates hemicellulose degradation in the archaeological wood, and the X-ray diffractograms show a considerable decrease in cellulose crystallinity and disorganization of the cellulose crystallites. The greater availability of active –OH groups means that the archaeological wood isotherms are above the juvenile and mature wood isotherms, and therefore the thermodynamic balance in the sorption of the archaeological wood is greater.
|
|
| 10. |
- Ghavidel, Amir, et al.
(författare)
-
Characterization of Archaeological European White Elm (Ulmus laevis P.) and Black Poplar(Populus nigra L.)
- 2020
-
Ingår i: Forests. - : MDPI. - 1999-4907. ; 11:12, s. 1-13
-
Tidskriftsartikel (refereegranskat)abstract
- The present study aims at characterization of freshly-cut and archaeological European white elm and poplar. The archaeological elm sample was buried at a depth of 8–10 m inside of soil with age approximation of ~1800–2000 years old, and the archaeological poplar sample was apart of a boat in a freshwater lake or river with age estimation of ~1000–1200 years. Alteration in the chemical structure of the elm and poplar samples due to the ageing process were confirmed by X-ray photoelectron spectroscopy (XPS). Both archaeological wood (AW) samples illustrated considerably lower cellulose crystallinity than the fresh samples as determined by X-ray diffraction. The sorption behavior of AW and fresh wood (FW) samples were evaluated by means of dynamic vapor sorption (DVS) analysis. Results exhibited a higher equilibrium moisture content (EMC) and sorption hysteresis values in archaeological elm and poplar as compared with the fresh samples. Higher hydrophilicity of the AW samples than the FW ones is attributed to their higher amorphous structure. The extensive degradation of AW samples were also confirmed by scanning electron microscopy (SEM) micrographs.
|
|
