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GL Beams Reinforced with Plywood in the Outer Layer
Glulam beams are increasingly used in the construction industry because of their high strength and the possibility of using round timber with smaller cross-sections. The load-bearing capacity of beams is strongly related to the quality of the outer layers and, in the case of wood, especially the tension zones. For these reasons, this study decided to replace the outer lamella with tensile plywood. The produced beams were subjected to static bending strength and modulus of elasticity evaluation. It was shown that the best static bending strength values were obtained for beams containing plywood in the tension layer. However, the change in structure in the tension zone of beams made of glued laminated timber results not only in an increase in the load capacity of elements produced in this way but also in a decrease in the range/range of the obtained results of bending strength. This way of modifying the construction of glued laminated beams allows a more rational use of available pine timber.
Properties of Lightweight Insulating Boards Produced from Triticale Straw Particles
Insulating materials made from straw are becoming increasingly popular in the construction industry. Straw can be used in the construction of buildings as uncompressed straw chips or in the form of compressed panels. This study aimed to determine the possibility of manufacturing boards from straw particles with densities in the range of 150–400 kg/m3, allowing favorable mechanical properties while simultaneously providing high thermal and acoustic insulation properties. The study also analyzed the influence of the degree of carpentry density on the quality of the manufactured boards. The study shows that insulation boards can be produced from straw particles with satisfactory properties already at densities in the range of 200–150 kg/m3. Boards with this density have a compressive strength of 150 kPa, thermal resistance of 0.033–0.046 W/(m·K), and a sound absorption coefficient above 0.31.
Akustyczna płyta komórkowa z rdzeniem listewkowym oraz sposób wytwarzania akustycznej płyty komórkowej z rdzeniem listewkowym
The Effect of Periodic Loading of Glued Laminated Beams on Their Static Bending Strength
Engineered wood products (EWP) such as glulam beams are gaining more and more popularity due to several advantages resulting from the wood itself, as well as the constant search for structural materials of natural origin. However, building materials face some requirements regarding their strength. Thus, the study aimed to assess the static bending strength of structural beams produced with the use of pine wood, after the periodic loading of approximately 80 kN for a year. The manufactured beams differed in the type of facing layers, i.e., pine timber with a high modulus of elasticity and plywood. The produced beams, regardless of their structure, are characterized by a similar static bending strength. Moreover, it has been shown that the loading of beams in the range of about 45% of their immediate capacity does not significantly affect their static bending strength and linear modulus of elasticity.
The Effect of Treatment with Fire Retardant on Properties of Birch Veneer and Manufactured Fire-Resistant Plywood
Kiln-drying effectiveness as influenced by moisture content and density variation within a Scots pine timber batch
APTES-Modified Nanocellulose as the Formaldehyde Scavenger for UF Adhesive-Bonded Particleboard and Strawboard
This work examines the possibility of applying non-modified nanocellulose and nanocellulose functionalized with 3-aminopropyltriethoxysilane (APTES) as a formaldehyde scavenger for commonly used urea-formaldehyde (UF) adhesive. The effect of silanization was determined with the use of Fourier transform infrared spectroscopy (FTIR), flame atomic absorption spectrometry (FAAS), and elemental analysis. Moreover, the ability of cellulosic nanoparticles to absorb the formaldehyde from an aqueous solution was investigated. After homogenization, cured UF adhesives were examined with the use of FTIR, energy-dispersive spectroscopy (SEM-EDS), and the perforator method to determine the content of formaldehyde. Manufactured boards made of rape straw particles and wood particles were tested in terms of their physico-mechanical properties and formaldehyde emission. Studies have shown that the applied method of silanization was effective. Furthermore, in the case of non-modified nanocellulose, no sign of formaldehyde scavenging ability was found. However, the functionalization of cellulosic nanoparticles with APTES containing an amino group led to the significant reduction of formaldehyde content in both the aqueous solution and the UF adhesive. The mechanical properties of both strawboards and particleboards were improved due to the nanocellulose reinforcement; however, no effect of silanization was found. Nevertheless, functionalization with APTES contributed to a decrease in formaldehyde emission from boards, which was not found in the case of the introduction of non-modified cellulosic nanoparticles.
Quality and Dimensional Parameters of Large-Sized Pine Timber in View of Expectations of Polish Sawmill Industry
Changes in the processing directions of round wood require the selection of raw material with appropriate quality and dimensional characteristics. In the case of large-size pine wood, these parameters translate significantly into its value and material indicators. The purpose of the research was to verify the currently applied classification principles with respect to the expectations of the market of wood industry customers. The research was conducted using the direct survey method, taking into account the structure of processing and sorting of production of wood industry representatives. The basic dimensional and quality groups for coniferous wood were separated, with wood defects assigned to them, in accordance with the currently binding principles of the quality and dimensional classification conducted by the State Forests. The respondents pointed out the necessity of changes in the minimum dimensions for wood of higher quality classes and changes in admissibility of selected defects in wood of lower classes.
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.
Propolis extract as a bio-based modifier of urea-formaldehyde adhesive in particleboard production
The effect of urea-formaldehyde adhesive modification with propylamine on the properties of manufactured plywood
The Possibility of Using Pine Bark Particles in the Chipboard Manufacturing Process
This research evaluated the possibility of using sawmill by-products from the roundwood-processing line in the production of wood-based panels. Due to its number of favorable properties, interesting chemical composition and large reserves resulting from the lack of industrial applications, the research focused particularly on the use of bark. Manufactured variants of boards differed in the proportions of wood chips to bark (70:30, 60:40, 50:50). Moreover, the boards containing only wood chips and a mixture of chips and sawdust were used as references. Urea-formaldehyde adhesive mixed with ammonium nitrate as a hardener was applied as a binding agent for the boards. Based on the mechanical properties (modulus of elasticity, modulus of rupture, internal bonding), physical properties (density, thickness swelling, water absorption) and content and emission of formaldehyde, it was found that it is possible to produce boards characterized by good properties from sawmill by-products without advanced processing. Moreover, the use of bark instead of sawdust in order to increase the homogeneity of the cross-section allows one to obtain panels with significantly lower formaldehyde emission and water uptake.
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%.
Selected Mechanical Properties of Glue-Laminated Timber Produced from Locally Repaired Timber
This study aimed to evaluate the mechanical properties determined in a 4-point bending test of beams made of lumber from which knots had been locally removed and the resulting loss replaced with sound wood. Three sets of beams were prepared, which differed in the number of layers/lamellas and the position of the lamellas from which edge knots were removed. All the lamellas used in the tests were subjected to a modulus of elasticity assessment. In addition to the distribution of defects, it determined the position of a given piece in the beam structure. The tests showed that high mechanical properties could characterise the beams produced in this way, i.e., a modulus of elasticity close to 12 kN/mm2 and a strength above 40 N/mm2, if the lamellas without knots were located below the outer tension lamella. Significantly better results were obtained when PUR glue was used in the inserts rather than MUF. In this case, beams with an improved outer lamella in the tension zone using semi-circular inserts glued with PUR glue had an average strength of 34.6 N/mm2.
Modified Buckwheat Husk as a Filler for Urea–Formaldehyde Resin in Plywood Production
The aim of the presented research was to determine the suitability of both non-modified and modified buckwheat husk (BH) as a filler for urea–formaldehyde adhesive in plywood production. The effect of two modification methods, acetylation and silanization, was investigated. Infrared spectroscopy outcomes confirmed that both acetylation and silanization of the filler had occurred. Based on the results, it was found that the introduction of BH had a significant effect on both the adhesive properties and the characteristics of the manufactured plywood. The application of non-modified husks led to a reduction in viscosity and an extension of the gelation time, and the produced plywood boards were characterized by reduced bonding quality and increased delamination. Modification of the husk surface by acetylation and silanization with 3-aminopropyltriethoxysilane contributed to the noticeable improvement in the resin properties. On the other hand, the improvement in plywood properties, consisting of the increase in bonding quality and reduced delamination, was observed only in the case of the silanized husk. Furthermore, the use of non-modified and acetylated husk did not significantly influence the formaldehyde emission. The reduction in the investigated emission of formaldehyde was observed only in the case of variants containing 15 and 20% of silanized buckwheat husk.
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.
