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The effect of pressing parameters and hardener content on the properties of plywood bonded with propylamine-UF adhesive
Symetryczne i asymetryczne lekkie płyty z cząstek roślin jednorocznych oraz sposób wytwarzania lekkich i asymetrycznych płyt z cząstek roślin jednorocznych
Optimization of Isocyanate Content in PF/pMDI Adhesive for the Production of High-Performing Particleboards
Due to the fact that impregnation with fire retardant usually reduces the strength of the produced particleboards, this research was carried out to investigate whether it is possible to use phenol–formaldehyde (PF) resin modified using various amounts (0%, 5%, 10%, 15%, and 20%) of polymeric 4,4′-methylene diphenyl diisocyanate (pMDI) for this purpose. The need to optimize the addition of pMDI is particularly important due to health and environmental aspects and high price. Furthermore, the curing process of hybrid resins is still not fully explained, especially in the case of small loadings. Manufactured particleboards differed in the share of impregnated particles (50% and 100%). The mixture of potassium carbonate and urea was used as the impregnating solution. Based on the outcomes of hybrid resins properties, it was found that the addition of pMDI leads to the increase in solid content, pH, and viscosity of the mixtures, to the improvement in resin reactivity determined using differential scanning calorimetry and to the decrease in thermal stability in the cured state evaluated using thermogravimetric analysis. Moreover, particleboard property results have shown that using impregnated particles (both 50% and 100%) decreased the strength of manufactured boards bonded using neat PF resin. However, the introduction of pMDI allowed us to compensate for the negative impact of fire-retardant-treated wood and it was found that the optimal loading of pMDI for the board containing 50% of impregnated particles is 5% and for board made entirely of treated wood it is 10%.
Possibility of Using Wind Turbine Waste in Particleboard Manufacturing
Recent reports indicate that the development of electricity generation using wind turbines will continue to grow. Despite the long service life of wind turbine blades, their technological life comes to an end at a certain point. Currently, there is no industrial method for recycling them, and the proposed solutions need to consider a complete and comprehensive approach to this material. In many countries, these blades are stored in special landfills and await proposals for rational recycling. It has been proposed that this recyclable yet still troublesome raw material be used in building sheathing boards. Sheathing boards used in the construction industry have a relatively long lifecycle. Three types of polymer chips and two resins, i.e., PF and MUF, were used in the study. The boards’ quality was assessed per the standards specified for particle boards. The resulting boards were characterized by strengths above 20 N/mm2 and an elastic modulus close to 4000 N/mm2. Slightly better results were obtained with the MUF resin.
Selected Chemical and Physical Properties of Pine Wood Chips Inoculated with Aspergillus and Penicillium Mold Fungi
Mold fungi representing genera of Penicillium and Aspergillus commonly develop on the surface of freshly harvested wood chips during storage. As a result, they are often considered as low-quality material and intended for incineration. Thus, the aim of the present study was to investigate the effect of wood chips infestation with mold fungi representing genera of Aspergillus and Penicillium on their basic chemical and physical properties, such as: chemical structure (evaluated with FTIR spectroscopy), mass loss and hygroscopicity, after an incubation of 3, 6 and 9 weeks. Based on the visual assessment and ergosterol content analysis, it was found that inoculation of wood chips with molds led to the intense fungal development on their surface. However, as observed in FTIR spectra, the presence of molds caused no changes in wood chemical structure. Furthermore, no mass loss and no significant increase in the hygroscopicity of wood were observed. Therefore, pine wood chips overgrown by studied genera of fungi seem to be a valuable material for various applications.
Wood Particles of Various Sizes from Primary Wood Processing as Filler in Rigid Polyurethane Foams
Experimental Analysis of Bonding in Steel Glued into Pine Timber
Combining steel with wood has been practised for many years. The issue is related to two main areas, i.e., bonding steel elements with wood so that they serve as connectors facilitating the assembly of wood elements and bonding steel elements to wood beams to improve their load-bearing capacity. In the first case, the adhesives used may be relatively expensive and more difficult to apply, whereas in the second one, especially when steel elements are glued inside the glulam (GL) beams, it is better if the adhesives used are more accessible to apply and cheaper. As it seems rational to reinforce wood with high-modulus ties, research has been carried out to compare the connection quality of commercially available adhesives that can be used for this purpose. Moreover, thermosetting adhesives have been applied as an alternative and cheaper solution. Thermostat adhesives also have a high pH of the bond, which prevents the steel from rusting. The research shows that the load-bearing capacity of the bond depends on whether the bars are ribbed or sheet metal. Moreover, among thermosetting adhesives, the most favourable load-bearing values were obtained using a mixture of PF/pMDI (phenol formaldehyde resin/polymeric diphenylmethane diisocyanate) and powder from recycled tyres. The shear strength of these joints was 1.63 N/mm2 and 3.14 N/mm2 for flat specimens and specimens with ribbed bars, respectively.
Sposób wytwarzania płyt kompozytowych z cząstek lignocelulozowych i polimerów termoplastycznych i płyta wytworzona tym sposobem
Changes in the Characteristics of Pine Logging Residue during Storage in Forest Stands
A significant amount of logging residue is produced during roundwood harvesting. Logs are often left in forest sites due to, for example, ecological or logistical aspects. Taking into account the fact that the number of studies focused on changes in the properties of the residue is very low, it was decided to conduct research on the effect of a three-year storage period in forest stands on the chemical properties and energy potential of the wood. The research design allowed for the determination of changes during up to three years of storage. The performed analysis showed a highly negative impact on the characteristics of the material. These adverse effects were probably caused by the activity of microorganisms such as fungi and bacteria, as evidenced by the increased concentrations of ergosterol and low-molecular-weight organic acids. Moreover, it was found that wood stored for three years was characterized by a lower cellulose content; an increased percentage of lignin; a reduced content of sterols (desmosterol, stigmasterol, lanosterol and β-sitosterol) and phenolic acids; and reduced antioxidant activity, as determined with the ABTS+ method. Storing logs also led to a reduction in the energy potential of the residues, as shown by a reduction in net and gross calorific value and an increased ash content.
The effect of storage conditions on the strength characteristic of glulam beams
Despite many outdoors applications, the number of works aimed to determine the effect of changing conditions on the properties of glulam beams, in particular those produced in non-standard arrangements, is few. Therefore, the aim of this study was to assess changes in flexural strength properties (MOE, MOR) of the beams stored for 30 months in varying conditions. Analyzed variants of pine GLT beams included five-meter-long structural elements reinforced with oak timber, high-quality pine timber and steel rods stored both in the roofed shed outdoors and inside the climatic chamber. Moisture content of the beam varied significantly depending on the placement of the sensors (on the surface or inside the beam). The average modulus of elasticity after 30 months of storage decreased by approx. 7% compared to initial values. The results varied depending on both the assumed beam arrangement and the applied conditions.
Effect of lysine-functionalized nanocellulose on urea-formaldehyde adhesive performance in particleboard production
Coffee silverskin and cocoa pod husk modified with methacrylic acid as fillers for the urea-formaldehyde resin in plywood production
The tea leaves as a filler for uf resin plywood production
The addition of green tea leaves fractions < 0.315 mm as afiller to urea-formaldehyde resin to reduction of emission of formaldehyde from three-layer birch plywood was investigated. Moreover, other properties such as bonding quality and water resistance of plywood were investigated. It was found that green tea had an ability to absorb formaldehyde. This phenomenon was caused by phenolic compounds contained in green tea leaves. The addition of green tea in the amount of 20% and 25% resulted in a decrease in formaldehyde emission fromplywood comparing to the reference sample. Thebonding quality test showed that the addition of tea leaves as a filler did not affect thestrength properties of the tested bond lines.
The Effect of Treatment with Fire Retardant on Properties of Birch Veneer and Manufactured Fire-Resistant Plywood
Properties of fiber-gypsum composite formed on the basis of hemp (Cannabis sativa L.) fibers grown in Poland and natural gypsum
: Properties of fiber-gypsum composite formed on the basis of hemp (Cannabis sativa L.) fibers grown in Poland and natural gypsum. The popularity of composites reinforced with natural fibers is constantly growing and therefore, they are a subject of many scientific works as well. An example of interesting concept is the use of hemp fibers to reinforce a gypsum matrix and therefore, presented study was aimed to determine the effect of their content on the properties of resultant composites. Moreover, the influence of setting temperature was also investigated. The scope of the research included determination of properties such as: density, setting time, bending strength, modulus of elasticity and thermal conductivity coefficient. Studies have shown that as the amount introduced fibers increases, the density of manufactured composites decreases. Furthermore, increase in the content of hemp causes a significant extension in setting time of the gypsum matrix. Based on the outcomes of mechanical properties, it was found that the optimal content of fibers is 4% and further increase in their share results in a deterioration of flexural strength characteristics. The increase in a setting temperature leads to thereduction in their bending strength and modulus of elasticity. Composites reinforced with hemp fibers demonstrate significantly improved thermal insulation properties
The effect of the tree dieback process on the mechanical properties of pine (Pinus sylvestris L.) wood
As a result of the progressing climate changes, there is an increase in the volume of pine deadwood harvested each year from Polish forests. Its presence is an important part of the forest ecosystem; however, there are some indications that the material obtained from dying trees can be characterized by lower quality and properties. Taking into account the growing issue of tree dieback, the volume of pine wood annually harvested in Poland, and the importance of wooden products from an economic standpoint, preliminary research aimed at recognizing the process and its effect on the mechanical properties was conducted. Model trees in Brzeg Forest District were selected based on the crown defoliation. The properties of wood obtained from trees representing three different categories of soundness were determined according to the relevant standards. Based on the results of density, modulus of elasticity, bending strength, and compressive strength, it was found that there were statistically significant differences in wood quality depending on the condition of the tree. The results were particularly interesting in the case of compressing strength, where a healthy tree of lower density showed a similar strength to a dying tree with a much higher density.
