Specific gas permeability of normal and nanosilver-impregnated solid wood species as influenced by heat-treatment

The effect of heat treatment at 50 and up to 150°C was studied on dowel-shape specimens prepared from beech (Fagus orientalis), poplar (Populus nigra), and fir (Abies alba) wood. Specimens were cut into two diameter sizes (18 and 25mm) to explore the effect of diameter size on permeability. Separate sets of specimens from each size and species were prepared to be first impregnated with a 200 ppm aqueous nanosilver (NS) suspension to investigate the effect of facilitated heat-transfer on permeability at different temperatures. Specimens were heated in five consecutive steps at 50, 75, 100, 125, and 150°C and for 24 hours in each step. High variance was found in the specific gas permeability between each treatment group, thus indicating probable high fluctuation in settlement of extractives at different spots of a log. Heat treatment only affected gas permeability at the first steps of heating (50 and 75°C), where loss of moisture content resulted in a permeability increase in nearly all species. Consecutive steps of heating up to 150°C did not significantly affect the permeability in either normal or NS-impregnated specimens

Effects of adhesive and loading directions on the load-carrying capacity of V-nails

Effects of tensile and compression loading on the overall strength of two miter frame corner joints, namely V-nail and dovetail joints, with and without adhesive were studied for medium-density fiberboard and particleboard. Two sizes of V-nails were chosen, sizes 7 and 10. Tensile and compression load-carrying capacity values were measured on the internal and external corners of the joints. Results showed that both wood-composites had greater load-carrying capacities for compression stress in comparison to tensile stress. Medium-density fiberboard demonstrated higher strength compared to particleboard specimens because of its higher compactness of fibers and more integrity in the composite matrix. Application of adhesive resulted in a significant increase in the strength of all joints and both composites. The increase in medium-density fiberboard was significantly higher in comparison to particleboard because lower permeability in medium-density fiberboard did not let adhesive to be uselessly penetrated into the texture. In particleboard specimens, however, adhesive penetrated into the voids and spaces in the composite, and the adhesive line was weakened between the surfaces of the composite bodies. It was concluded that V-nails are recommended for craftsmen in case adhesive is used. However, dovetail joints provide higher strength if the production process necessitates not to use adhesive in joints

Study on the effects of wood flour geometry on physical and mechanical properties of wood-plastic composites

The present study is focused on the effects of the shape and size of Fagus orientalis wood flour on physical and mechanical properties of HDPE based wood plastic composites (WPC). Variables included two mesh sizes (20 and 60), as well as five different contents of ground shavings (0, 25, 50,75, and 100%) mixed with sawdust; totally 10 treatments. HDPT content was 40% in all formulations. Panels were compression molded and physical and mechanical tests were carried out in accordance with ASTM D2240 standard specifications. Results showed that mesh size can only significantly affect the hardness in the studied wood-plastic composites. On the other hand, increasing the proportion of the ground shavings possessing higher aspect ratio (l/d) increased both flexural strength and hardness. This increasing effect however was not observed for ground shavings beyond 50%. It was also concluded that while the addition of ground shavings up to 50% could improve the mechanical properties, higher proportions would reduce some of the properties, particularly the impact strength. In was concluded that the panel made of 50% wood flour combined with 50% ground shavings exhibited overall suitableproperties for most applications

Effects of sepiolite addition to acrylic-latex paint on pull-off adhesion strength in nanosilver-impregnated and thermally-modified beech (Fagus orientalis L.) wood

Sepiolite is a silicate mineral that improves the fire properties in solid wood when mixed with a water-based coating. The present study was carried out to investigate and evaluate the effects of sepiolite addition to acrylic-latex paint on the pull-off adhesion strength, as an important characteristic of paints and finishes used in the modern furniture industry and historical furniture as well for preservation and restoration of heritage objects. Sepiolite was added at the rate of 10, and brushed onto plain-sawn beech (Fagus orientalis L.) wood specimens, unimpregnated and impregnated with a 400 ppm silver nano-suspension, which were further thermally modified at 185 °C for 4 h. The results showed that thermal modification had a decreasing effect on the pull-off adhesion strength, primarily as a result of the thermal degradation of cell-wall polymers (mostly hemicelluloses). Still, a decreased wettability as a result of condensation and plasticization of lignin was also partially influential. Based on the obtained results,thermal modification was found to have a significant influence on pull-off adhesion strength. Sepiolite addition had a decreasing effectin all treatments, though the effect was not statistically significant in all treatments. The maximum and minimum decreases due to sepiolite addition were observed in the unimpregnated control (21) and the thermally-modified NS-impregnated (4) specimens. Other aspects of the sepiolite addition, and further studies that cover different types of paints and coatings, should be evaluated before coming to a final firm conclusion in this regard

Effects of Wollastonite on Fire Properties of Particleboard Made from Wood and Chicken Feather Fibers

The present study was carried out primarily to investigate the fire properties of particleboards with 5% and 10% feather content. With regard to the flammability of chicken feathers, separate sets of panels were produced with 10% wollastonite content to determine to what extent it could help mitigate the negative effects of the addition of flammable feathers on the fire properties. It was concluded that the inclusion of 5% of chicken feathers can be considered the optimum level, enough to procure part of the ever-growing needs for new sources of raw material in particleboard manufacturing factories, without sacrificing the important fire properties. Moreover, the addition of 10% wollastonite is recommended to significantly improve the fire properties, making the panels more secure in applications with higher risks of fire. It is further stated thata chicken feather content of 10% is not recommended as it significantly deteriorates all properties (including physical, mechanical, and fire properties)

Wollastonite to Improve Fire Properties in Medium-Density Fiberboard Made from Wood and Chicken Feather Fibers

Poultry is a crucial global protein source.However, processing creates sizable quantities of feathers as a by-product. Identifying suitable uses for these feathers poses a major challenge. One possible use would be as an extender in medium density fiberboards (MDF). At the same time, feathers might also modify the inherent fire resistance of the resulting panels, suggesting the need for additives to enhance fire performance. The potential for using feathers to supplement wood in MDF panels was evaluated in conjunction with the addition of wollastonite. The effects of using 5% or 10% feathers with or without 10% wollastonite were investigated. Adding 5% feathers did affect properties. However, simultaneous addition of 10% wollastonite resulted in panels with improved fire performance properties and increased the ability of panels to dissipate heat. The results suggest that feathers could be a resource for extending timber supplies for MDF production, especially with wollastonite to improve fire performance

Specific gas permeability of normal and nanosilver-impregnated solid wood species as influenced by heat-treatment

The effect of heat treatment at 50 and up to 150°C was studied on dowel-shape specimens prepared from beech (Fagus orientalis), poplar (Populus nigra), and fir (Abies alba) wood. Specimens were cut into two diameter sizes (18 and 25mm) to explore the effect of diameter size on permeability. Separate sets of specimens from each size and species were prepared to be first impregnated with a 200 ppm aqueous nanosilver (NS) suspension to investigate the effect of facilitated heat-transfer on permeability at different temperatures. Specimens were heated in five consecutive steps at 50, 75, 100, 125, and 150°C and for 24 hours in each step. High variance was found in the specific gas permeability between each treatment group, thus indicating probable high fluctuation in settlement of extractives at different spots of a log. Heat treatment only affected gas permeability at the first steps of heating (50 and 75°C), where loss of moisture content resulted in a permeability increase in nearly all species. Consecutive steps of heating up to 150°C did not significantly affect the permeability in either normal or NS-impregnated specimens. Keywords: Beech, poplar, fir, longitudinal permeability, wood-modificatio

Effect of silver nanoparticles on hardness in medium-density fiberboard (MDF)

Effect of silver nanoparticles on hardness in medium-density fiberboard (MDF) was studied here. A 400 ppm aqueous nanosilver suspension was used at three consumption levels of 100, 150, and 200 mL kg-1, based on the dry weight of wood fibers; the results were then compared with the control panels. The size range of silver nanoparticles was 30-80 nm. Composite mats were hot-pressed for 6, 8, and 10 min. Results showed that the uniform and even dispersion of nanoparticles throughout the MDF-matrix significantly contributed to an increase in the hardness at lower hot-press time of 6 min. In the longer hot-press times, however, over-heating of the mat resulted in significant a decrease of hardness values. Significant high correlation was observed between water absorption and thickness swelling

EFFECTS OF IMPREGNATION WITH STYRENE AND NANO-ZINC OXIDE ON FIRE-RETARDING, PHYSICAL, AND MECHANICAL PROPERTIES OF POPLAR WOOD

Nanoparticles have been vastly applied in wood polymer composites (WPCs) in the recent years to improve some of the drawbacks of solid wood species. In the present study, the effects of ZnO nanoparticles on fire retarding, physical, and mechanical properties of polymerized poplar wood were investigated. Poplar specimens were impregnated with styrene monomer, containing four different contents of nano-zinc oxide (ZnO) (0, 0.5, 1 and 1.5%, based on the dry weight of monomer). Results of the scanning electron microscopy (SEM) showed homogeneous dispersion of ZnO nanoparticles in the WPC matrix. Nano-zinc oxide improved physical properties such as dimensional stability and water absorption. Moreover, mechanical properties increased in comparison to the control specimens. The impregnation process also significantly improved some of the fire-retarding properties, including the ignition time; however, the flammability nature of styrene aggravated some others, such as carbonized area. It was concluded that, although most of the properties were improved, the final application of WPC should be taken in to consideration before making decision on whether or not to impregnate populus wood with styrene