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The purpose of this study was to evaluate the feasibility of using magnesium and sodium lignosulfonates (LS) in the production of particleboards, used pure and in mixtures with urea-formaldehyde (UF) resin. Polymeric 4,4′-diphenylmethane diisocyanate (pMDI) was used as a crosslinker. In order to evaluate the effect of gradual replacement of UF by magnesium lignosulfonate (MgLS) or sodium lignosulfonate (NaLS) on the physical and mechanical properties, boards were manufactured in the laboratory with LS content varying from 0% to 100%. The effect of LS on the pH of lignosulfonate-urea-formaldehyde (LS-UF) adhesive compositions was also investigated. It was found that LS can be effectively used to adjust the pH of uncured and cured LS-UF formulations. Particleboards bonded with LS-UF adhesive formulations, comprising up to 30% LS, exhibited similar properties when compared to boards bonded with UF adhesive. The replacement of UF by both LS types substantially deteriorated the water absorption and thickness swelling of boards. In general, NaLS-UF-bonded boards had a lower formaldehyde content (FC) than MgLS-UF and UF-bonded boards as control. It was observed that in the process of manufacturing boards using LS adhesives, increasing the proportion of pMDI in the adhesive composition can significantly improve the mechanical properties of the boards. Overall, the boards fabricated using pure UF adhesives exhibited much better mechanical properties than boards bonded with LS adhesives. Markedly, the boards based on LS adhesives were characterised by a much lower FC than the UF-bonded boards. In the LS-bonded boards, the FC is lower by 91.1% and 56.9%, respectively, compared to the UF-bonded boards. The boards bonded with LS and pMDI had a close-to-zero FC and reached the super E0 emission class (≤1.5 mg/100 g) that allows for defining the laboratory-manufactured particleboards as eco-friendly composites.
Pavlo Bekhta; Gregory Noshchenko; Roman Réh; Lubos Kristak; Ján Sedliačik; Petar Antov; Radosław Mirski; Viktor Savov. Properties of Eco-Friendly Particleboards Bonded with Lignosulfonate-Urea-Formaldehyde Adhesives and pMDI as a Crosslinker. Materials 2021, 14, 4875 .
AMA StylePavlo Bekhta, Gregory Noshchenko, Roman Réh, Lubos Kristak, Ján Sedliačik, Petar Antov, Radosław Mirski, Viktor Savov. Properties of Eco-Friendly Particleboards Bonded with Lignosulfonate-Urea-Formaldehyde Adhesives and pMDI as a Crosslinker. Materials. 2021; 14 (17):4875.
Chicago/Turabian StylePavlo Bekhta; Gregory Noshchenko; Roman Réh; Lubos Kristak; Ján Sedliačik; Petar Antov; Radosław Mirski; Viktor Savov. 2021. "Properties of Eco-Friendly Particleboards Bonded with Lignosulfonate-Urea-Formaldehyde Adhesives and pMDI as a Crosslinker." Materials 14, no. 17: 4875.
The potential of ammonium lignosulfonate (ALS) as an eco-friendly additive to urea–formaldehyde (UF) resin for manufacturing high-density fiberboard (HDF) panels with acceptable properties and low free formaldehyde emission was investigated in this work. The HDF panels were manufactured in the laboratory with very low UF resin content (4%) and ALS addition levels varying from 4% to 8% based on the mass of the dry wood fibers. The press factor applied was 15 s·mm−1. The physical properties (water absorption and thickness swelling), mechanical properties (bending strength, modulus of elasticity, and internal bond strength), and free formaldehyde emission were evaluated in accordance with the European standards. In general, the developed HDF panels exhibited acceptable physical and mechanical properties, fulfilling the standard requirements for HDF panels for use in load-bearing applications. Markedly, the laboratory-produced panels had low free formaldehyde emission ranging from 2.0 to 1.4 mg/100 g, thus fulfilling the requirements of the E0 and super E0 emission grades and confirming the positive effect of ALS as a formaldehyde scavenger. The thermal analyses performed, i.e., differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and derivative thermogravimetry (DTG), also confirmed the main findings of the research. It was concluded that ALS as a bio-based, formaldehyde-free adhesive can be efficiently utilized as an eco-friendly additive to UF adhesive formulations for manufacturing wood-based panels under industrial conditions.
Petar Antov; Viktor Savov; Neno Trichkov; Ľuboš Krišťák; Roman Réh; Antonios N. Papadopoulos; Hamid R. Taghiyari; Antonio Pizzi; Daniela Kunecová; Marina Pachikova. Properties of High-Density Fiberboard Bonded with Urea–Formaldehyde Resin and Ammonium Lignosulfonate as a Bio-Based Additive. Polymers 2021, 13, 2775 .
AMA StylePetar Antov, Viktor Savov, Neno Trichkov, Ľuboš Krišťák, Roman Réh, Antonios N. Papadopoulos, Hamid R. Taghiyari, Antonio Pizzi, Daniela Kunecová, Marina Pachikova. Properties of High-Density Fiberboard Bonded with Urea–Formaldehyde Resin and Ammonium Lignosulfonate as a Bio-Based Additive. Polymers. 2021; 13 (16):2775.
Chicago/Turabian StylePetar Antov; Viktor Savov; Neno Trichkov; Ľuboš Krišťák; Roman Réh; Antonios N. Papadopoulos; Hamid R. Taghiyari; Antonio Pizzi; Daniela Kunecová; Marina Pachikova. 2021. "Properties of High-Density Fiberboard Bonded with Urea–Formaldehyde Resin and Ammonium Lignosulfonate as a Bio-Based Additive." Polymers 13, no. 16: 2775.
The ongoing transition to a low-carbon, sustainable forest-based economy, and the adoption of circular bioeconomy principles in the wood-processing industry is associated with the optimization of natural resources, application of environmentally sustainable production technologies, adoption of technological and organizational innovations, and increased economic efficiency and competitiveness. The implementation of all these measures can help to reach the biggest challenge of our time in the fight against climate change in a cost-effective and competitive way. The aim of this study was to estimate the technical efficiency of wood-processing companies in the Slovak Republic and the Republic of Bulgaria by applying data envelopment analysis (DEA) and the Malmquist productivity index (MPI), and to reveal some factors for efficiency improvements. The economic efficiency evaluation based on official data was performed using selected indices of four wood-processing companies in each country in the period 2014–2018. The study implemented an output-oriented DEA model with constant returns to scale as a nonparametric linear approach for measuring the efficiency of production decision-making units (DMUs). The results obtained revealed that the studied Slovak companies were more efficient with better management in terms of machinery planning and overhead utilization. Markedly, the Bulgarian companies achieved better materials management and current planning quality. Increased economic efficiency of wood-processing enterprises in both countries can be realized through investments in innovative technological improvements, and enhanced research and development activities.
Stanislava Krišťáková; Nikolay Neykov; Petar Antov; Mariana Sedliačiková; Roman Reh; Aureliu-Florin Halalisan; Iveta Hajdúchová. Efficiency of Wood-Processing Enterprises—Evaluation Based on DEA and MPI: A Comparison between Slovakia and Bulgaria for the Period 2014–2018. Forests 2021, 12, 1026 .
AMA StyleStanislava Krišťáková, Nikolay Neykov, Petar Antov, Mariana Sedliačiková, Roman Reh, Aureliu-Florin Halalisan, Iveta Hajdúchová. Efficiency of Wood-Processing Enterprises—Evaluation Based on DEA and MPI: A Comparison between Slovakia and Bulgaria for the Period 2014–2018. Forests. 2021; 12 (8):1026.
Chicago/Turabian StyleStanislava Krišťáková; Nikolay Neykov; Petar Antov; Mariana Sedliačiková; Roman Reh; Aureliu-Florin Halalisan; Iveta Hajdúchová. 2021. "Efficiency of Wood-Processing Enterprises—Evaluation Based on DEA and MPI: A Comparison between Slovakia and Bulgaria for the Period 2014–2018." Forests 12, no. 8: 1026.
The effects of using 100% larch bark (Larix decidua Mill) as a raw material for composite boards on the thermophysical properties of this innovative material were investigated in this study. Panels made of larch bark with 4–11 mm and 10–30 mm particle size, with ground bark oriented parallel and perpendicular to the panel’s plane at densities varying from 350 to 700 kg/m3 and bonded with urea-formaldehyde adhesive were analyzed for thermal conductivity, thermal resistivity and specific heat capacity. It was determined that there was a highly significant influence of bulk density on the thermal conductivity of all the panels. With an increase in the particle size, both parallel and perpendicular to the panel´s plane direction, the thermal conductivity also increased. The decrease of thermal diffusivity was a consequence of the increasing particle size, mostly in the parallel orientation of the bark particles due to the different pore structures. The specific heat capacity is not statistically significantly dependent on the density, particle size, glue amount and particle orientation.
Lubos Kristak; Ivan Ruziak; Eugenia Tudor; Marius Barbu; Günther Kain; Roman Reh. Thermophysical Properties of Larch Bark Composite Panels. Polymers 2021, 13, 2287 .
AMA StyleLubos Kristak, Ivan Ruziak, Eugenia Tudor, Marius Barbu, Günther Kain, Roman Reh. Thermophysical Properties of Larch Bark Composite Panels. Polymers. 2021; 13 (14):2287.
Chicago/Turabian StyleLubos Kristak; Ivan Ruziak; Eugenia Tudor; Marius Barbu; Günther Kain; Roman Reh. 2021. "Thermophysical Properties of Larch Bark Composite Panels." Polymers 13, no. 14: 2287.
The potential of tree bark, a by-product of the woodworking industry, has been studied for more than seven decades. Bark, as a sustainable raw material, can replace wood or other resources in numerous applications in construction. In this study, the acoustic properties of bark-based panels were analyzed. The roles of the particle size (4–11 mm and 10–30 mm), particle orientation (parallel and perpendicular) and density (350–700 kg/m3) of samples with 30 mm and 60 mm thicknesses were studied at frequencies ranging from 50 to 6400 Hz. Bark-based boards with fine-grained particles have been shown to be better in terms of sound absorption coefficient values compared with coarse-grained particles. Bark composites mixed with popcorn bonded with UF did not return the expected results, and it is not possible to recommend this solution. The best density of bark boards to obtain the best sound absorption coefficients is about 350 kg/m3. These lightweight panels achieved better sound-absorbing properties (especially at lower frequencies) at higher thicknesses. The noise reduction coefficient of 0.5 obtained a sample with fine particles with a parallel orientation and a density of around 360 kg/m3.
Eugenia Tudor; Lubos Kristak; Marius Barbu; Tomáš Gergeľ; Miroslav Němec; Günther Kain; Roman Réh. Acoustic Properties of Larch Bark Panels. Forests 2021, 12, 887 .
AMA StyleEugenia Tudor, Lubos Kristak, Marius Barbu, Tomáš Gergeľ, Miroslav Němec, Günther Kain, Roman Réh. Acoustic Properties of Larch Bark Panels. Forests. 2021; 12 (7):887.
Chicago/Turabian StyleEugenia Tudor; Lubos Kristak; Marius Barbu; Tomáš Gergeľ; Miroslav Němec; Günther Kain; Roman Réh. 2021. "Acoustic Properties of Larch Bark Panels." Forests 12, no. 7: 887.
The potential of using residual softwood fibers from the pulp and paper industry for producing eco-friendly, zero-formaldehyde fiberboard panels, bonded with calcium lignosulfonate (CLS) as a lignin-based, formaldehyde free adhesive, was investigated in this work. Fiberboard panels were manufactured in the laboratory by applying CLS addition content ranging from 8% to 14% (on the dry fibers). The physical and mechanical properties of the developed composites, i.e., water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), as well as the free formaldehyde emission, were evaluated according to the European norms. In general, only the composites, developed with 14% CLS content, exhibited MOE and MOR values, comparable with the standard requirements for medium-density fiberboards (MDF) for use in dry conditions. All laboratory-produced composites demonstrated significantly deteriorated moisture-related properties, i.e., WA (24 h) and TS (24 h), which is a major drawback. Noticeably, the fiberboards produced had a close-to-zero formaldehyde content, reaching the super E0 class (≤1.5 mg/100 g), with values, ranging from 0.8 mg/100 g to 1.1 mg/100 g, i.e., equivalent to formaldehyde emission of natural wood. The amount of CLS adhesive had no significant effect on formaldehyde content.
Petar Antov; L’Uboš Krišt’ák; Roman Réh; Viktor Savov; Antonios Papadopoulos. Eco-Friendly Fiberboard Panels from Recycled Fibers Bonded with Calcium Lignosulfonate. Polymers 2021, 13, 639 .
AMA StylePetar Antov, L’Uboš Krišt’ák, Roman Réh, Viktor Savov, Antonios Papadopoulos. Eco-Friendly Fiberboard Panels from Recycled Fibers Bonded with Calcium Lignosulfonate. Polymers. 2021; 13 (4):639.
Chicago/Turabian StylePetar Antov; L’Uboš Krišt’ák; Roman Réh; Viktor Savov; Antonios Papadopoulos. 2021. "Eco-Friendly Fiberboard Panels from Recycled Fibers Bonded with Calcium Lignosulfonate." Polymers 13, no. 4: 639.
The potential of using ground birch (Betula verrucosa Ehrh.) bark as an eco-friendly additive in urea-formaldehyde (UF) adhesives for plywood manufacturing was investigated in this work. Five-ply plywood panels were fabricated in the laboratory from beech (Fagus sylvatica L.) veneers bonded with UF adhesive formulations comprising three addition levels of birch bark (BB) as a filler (10%, 15%, and 20%). Two UF resin formulations filled with 10% and 20% wheat flour (WF) were used as reference samples. The mechanical properties (bending strength, modulus of elasticity and shear strength) of the laboratory-fabricated plywood panels, bonded with the addition of BB in the adhesive mixture, were evaluated and compared with the European standard requirements (EN 310 and EN 314-2). The mechanical strength of the plywood with the addition of BB in the adhesive mixture is acceptable and met the European standard requirements. Markedly, the positive effect of BB in the UF adhesive mixture on the reduction of formaldehyde emission from plywood panels was also confirmed. Initially, the most significant decrease in formaldehyde release (up to 14%) was measured for the plywood sample, produced with 15% BB. After four weeks, the decrease in formaldehyde was estimated up to 51% for the sample manufactured with 20% BB. The performed differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and derivative thermogravimetry (DTG), also confirmed the findings of the study. As this research demonstrated, BB as a waste or by-product of wood processing industry, can be efficiently utilized as an environmentally friendly, inexpensive alternative to WF as a filler in UF adhesive formulations for plywood manufacturing.
Roman Réh; Ľuboš Krišťák; Ján Sedliačik; Pavlo Bekhta; Monika Božiková; Daniela Kunecová; Vlasta Vozárová; Eugenia Tudor; Petar Antov; Viktor Savov. Utilization of Birch Bark as an Eco-Friendly Filler in Urea-Formaldehyde Adhesives for Plywood Manufacturing. Polymers 2021, 13, 511 .
AMA StyleRoman Réh, Ľuboš Krišťák, Ján Sedliačik, Pavlo Bekhta, Monika Božiková, Daniela Kunecová, Vlasta Vozárová, Eugenia Tudor, Petar Antov, Viktor Savov. Utilization of Birch Bark as an Eco-Friendly Filler in Urea-Formaldehyde Adhesives for Plywood Manufacturing. Polymers. 2021; 13 (4):511.
Chicago/Turabian StyleRoman Réh; Ľuboš Krišťák; Ján Sedliačik; Pavlo Bekhta; Monika Božiková; Daniela Kunecová; Vlasta Vozárová; Eugenia Tudor; Petar Antov; Viktor Savov. 2021. "Utilization of Birch Bark as an Eco-Friendly Filler in Urea-Formaldehyde Adhesives for Plywood Manufacturing." Polymers 13, no. 4: 511.
The potential of producing eco-friendly, formaldehyde-free, high-density fiberboard (HDF) panels from hardwood fibers bonded with urea-formaldehyde (UF) resin and a novel ammonium lignosulfonate (ALS) is investigated in this paper. HDF panels were fabricated in the laboratory by applying a very low UF gluing factor (3%) and ALS content varying from 6% to 10% (based on the dry fibers). The physical and mechanical properties of the fiberboards, such as water absorption (WA), thickness swelling (TS), modulus of elasticity (MOE), bending strength (MOR), internal bond strength (IB), as well as formaldehyde content, were determined in accordance with the corresponding European standards. Overall, the HDF panels exhibited very satisfactory physical and mechanical properties, fully complying with the standard requirements of HDF for use in load-bearing applications in humid conditions. Markedly, the formaldehyde content of the laboratory fabricated panels was extremely low, ranging between 0.7–1.0 mg/100 g, which is, in fact, equivalent to the formaldehyde release of natural wood.
Petar Antov; Viktor Savov; Ľuboš Krišťák; Roman Réh; George I. Mantanis. Eco-Friendly, High-Density Fiberboards Bonded with Urea-Formaldehyde and Ammonium Lignosulfonate. Polymers 2021, 13, 220 .
AMA StylePetar Antov, Viktor Savov, Ľuboš Krišťák, Roman Réh, George I. Mantanis. Eco-Friendly, High-Density Fiberboards Bonded with Urea-Formaldehyde and Ammonium Lignosulfonate. Polymers. 2021; 13 (2):220.
Chicago/Turabian StylePetar Antov; Viktor Savov; Ľuboš Krišťák; Roman Réh; George I. Mantanis. 2021. "Eco-Friendly, High-Density Fiberboards Bonded with Urea-Formaldehyde and Ammonium Lignosulfonate." Polymers 13, no. 2: 220.
This article deals with the laser cutting of wood and wood composites. The laser cutting of wood and wood composites is widely accepted and used by the wood industry (due to its many advantages compared to, e.g., saw cutting). The goal of this research was to optimize the cutting parameters of spruce wood (Pices abies L.) by a low-power CO2 laser. The influence of three factors was investigated, namely, the effect of the laser power (100 and 150 W), cutting speed (3, 6, and 9 mm·s−1), and number of annual rings (3–11) on the width of the cutting kerf on the top board, on the width of the cutting kerf on the bottom board, on the ratio of the cutting kerf width on the top and bottom of the board, on the width of the heat-affected area on both sides of the cutting kerf (this applies to the top and bottom of the board), and on the degree of charring. Analysis of variance (ANOVA) and correlation and regression analysis were used for developing a linear regression model without interactions and a quadratic regression model with quadratic interactions. Based on the developed models, the optimization of parameter settings of the investigated process was performed in order to achieve the final kerf quality. The improvement in the quality of the part ranged from 3% to more than 30%. The results were compared with other research dealing with the laser cutting of wood and wood composites.
Ivan Kubovský; Ľuboš Krišťák; Juraj Suja; Milada Gajtanska; Rastislav Igaz; Ivan Ružiak; Roman Réh. Optimization of Parameters for the Cutting of Wood-Based Materials by a CO2 Laser. Applied Sciences 2020, 10, 8113 .
AMA StyleIvan Kubovský, Ľuboš Krišťák, Juraj Suja, Milada Gajtanska, Rastislav Igaz, Ivan Ružiak, Roman Réh. Optimization of Parameters for the Cutting of Wood-Based Materials by a CO2 Laser. Applied Sciences. 2020; 10 (22):8113.
Chicago/Turabian StyleIvan Kubovský; Ľuboš Krišťák; Juraj Suja; Milada Gajtanska; Rastislav Igaz; Ivan Ružiak; Roman Réh. 2020. "Optimization of Parameters for the Cutting of Wood-Based Materials by a CO2 Laser." Applied Sciences 10, no. 22: 8113.
Wooden shingles are a traditional roofing material on many culturally important building artifacts. Currently, the roof space of many traditional buildings is used for residential purposes and, consequently, cold roof constructions with ventilation layers are applied. In this study, it is evaluated whether the moisture content of wooden shingles is adversely affected by such constructions, compared with unvented shingle roofs over cold attics and whether a temporary closing of the ventilation gaps at the eaves contributes to a lower wood moisture content. Various sensors were installed in and around a building with wooden shingles on a ventilated roof and temperature, air moisture, and air speed in the ventilation layer were measured throughout a year. The findings show that the air speed in the ventilation layer can be adjusted from 0.06 to 0.25 m/s depending on the layout of the eaves. A hygrothermal model was applied to evaluate the effects of different ventilation operation modes and cardinal orientations of the roof on the moisture content of the wooden shingles. The results show that roof ventilation results in a 1% lower shingle moisture content on average than an unventilated roof over a cold attic. Finally, it is shown that the wood moisture content repeatedly reaches dangerous levels above 25% throughout a year, which is worse on north-facing roofs and, hence, measures to increase the dry-out are relevant.
Günther Kain; Friedrich Idam; Franz Federspiel; Roman Réh; Ľuboš Krišťák. Suitability of Wooden Shingles for Ventilated Roofs: An Evaluation of Ventilation Efficiency. Applied Sciences 2020, 10, 6499 .
AMA StyleGünther Kain, Friedrich Idam, Franz Federspiel, Roman Réh, Ľuboš Krišťák. Suitability of Wooden Shingles for Ventilated Roofs: An Evaluation of Ventilation Efficiency. Applied Sciences. 2020; 10 (18):6499.
Chicago/Turabian StyleGünther Kain; Friedrich Idam; Franz Federspiel; Roman Réh; Ľuboš Krišťák. 2020. "Suitability of Wooden Shingles for Ventilated Roofs: An Evaluation of Ventilation Efficiency." Applied Sciences 10, no. 18: 6499.
The objective of this study was to investigate the sound absorption coefficient of bark-based insulation panels made of softwood barks Spruce (Picea abies (L.) H. Karst.) and Larch (Larix decidua Mill.) by means of impedance tube, with a frequency range between 125 and 4000 Hz. The highest efficiency of sound absorption was recorded for spruce bark-based insulation boards bonded with urea-formaldehyde resin, at a level of 1000 and 2000 Hz. The potential of noise reduction of larch bark-based panels glued with tannin-based adhesive covers the same frequency interval. The experimental results show that softwood bark, an underrated material, can substitute expensive materials that involve more grey energy in sound insulation applications. Compared with wood-based composites, the engineered spruce bark (with coarse-grained and fine-grained particles) can absorb the sound even better than MDF, particleboard or OSB. Therefore, the sound absorption coefficient values strengthen the application of insulation panels based on tree bark as structural elements for the noise reduction in residential buildings, and concurrently they open the new ways for a deeper research in this field.
Eugenia Mariana Tudor; Anna Dettendorfer; Günther Kain; Marius Catalin Barbu; Roman Réh; Ľuboš Krišťák. Sound-Absorption Coefficient of Bark-Based Insulation Panels. Polymers 2020, 12, 1012 .
AMA StyleEugenia Mariana Tudor, Anna Dettendorfer, Günther Kain, Marius Catalin Barbu, Roman Réh, Ľuboš Krišťák. Sound-Absorption Coefficient of Bark-Based Insulation Panels. Polymers. 2020; 12 (5):1012.
Chicago/Turabian StyleEugenia Mariana Tudor; Anna Dettendorfer; Günther Kain; Marius Catalin Barbu; Roman Réh; Ľuboš Krišťák. 2020. "Sound-Absorption Coefficient of Bark-Based Insulation Panels." Polymers 12, no. 5: 1012.
During production, thermally modified wood is processed using the same machining operations as unmodified wood. Machining wood is always accompanied with the creation of dust particles. The smaller they become, the more hazardous they are. Employees are exposed to a greater health hazard when machining thermally modified wood because a considerable amount of fine dust is produced under the same processing conditions than in the case of unmodified wood. The International Agency for Research on Cancer (IARC) states that wood dust causes cancer of the nasal cavity and paranasal sinuses and of the nasopharynx. Wood dust is also associated with toxic effects, irritation of the eyes, nose and throat, dermatitis, and respiratory system effects which include decreased lung capacity, chronic obstructive pulmonary disease, asthma and allergic reactions. In our research, granular composition of particles resulting from the process of longitudinal milling of heat-treated oak and spruce wood under variable conditions (i.e., the temperature of modification of 160, 180, 200 and 220 °C and feed rate of 6, 10 and 15 m.min−1) are presented in the paper. Sieve analysis was used to determine the granular composition of particles. An increase in fine particle fraction when the temperature of modification rises was confirmed by the research. This can be due to the lower strength of thermally modified wood. Moreover, a different effect of the temperature modification on granularity due to the tree species was observed. In the case of oak wood, changes occurred at a temperature of 160 °C and in the case of spruce wood, changes occurred at the temperatures of 200 and 220 °C. At the temperatures of modification of 200 and 220 °C, the dust fraction (i.e., that occurred in the mesh sieves, particles with the size ≤ 0.08 mm) ranged from 2.99% (oak wood, feed rate of 10 m.min−1) to 8.07% (spruce wood, feed rate of 6 m.min−1). Such particles might have a harmful effect on employee health in wood-processing facilities.
Alena Očkajová; Martin Kučerka; Richard Kminiak; Ľuboš Krišťák; Rastislav Igaz; Roman Réh. Occupational Exposure to Dust Produced when Milling Thermally Modified Wood. International Journal of Environmental Research and Public Health 2020, 17, 1478 .
AMA StyleAlena Očkajová, Martin Kučerka, Richard Kminiak, Ľuboš Krišťák, Rastislav Igaz, Roman Réh. Occupational Exposure to Dust Produced when Milling Thermally Modified Wood. International Journal of Environmental Research and Public Health. 2020; 17 (5):1478.
Chicago/Turabian StyleAlena Očkajová; Martin Kučerka; Richard Kminiak; Ľuboš Krišťák; Rastislav Igaz; Roman Réh. 2020. "Occupational Exposure to Dust Produced when Milling Thermally Modified Wood." International Journal of Environmental Research and Public Health 17, no. 5: 1478.
Ecofriendly wood-based materials are required by consumers at present. Decorative panels are part of a large group of wood-composite materials, and their environmental properties must not be neglected. More environmentally friendly decorative panels can be achieved by various methods. This paper describes a method of production from larch bark. Tree bark, as a byproduct of the wood industry, is one of the research topics that have gained interest in the last decade, especially for its applications in biobased lignocomposites, with regard to the shrinkage of wood resources. In the present work, the formaldehyde content of decorative boards based on larch bark (0.6 g/cm3) was analyzed when bonded with five different types of adhesive systems: urea-formaldehyde, polyvinyl acetate, the mixture of 70% urea-formaldehyde + 30% polyvinyl acetate, polyurethane, and tannin-based adhesive. A self-agglomerated board was also analyzed. The formaldehyde content of the larch-bark samples was determined with the perforator method (EN 120:2011), and findings showed that all tested samples reached the E1 classification (≤8 mg/100 oven dry). Moreover, 75% of the values of the corrected formaldehyde content were included in the super-E0 class (≤1.5 mg/100 oven dry). In the case of boards bonded with tannin-based adhesive, this natural polymer acted as a formaldehyde scavenger.
Eugenia Mariana Tudor; Marius Catalin Barbu; Alexander Petutschnigg; Roman Réh; Ľuboš Krišťák. Analysis of Larch-Bark Capacity for Formaldehyde Removal in Wood Adhesives. International Journal of Environmental Research and Public Health 2020, 17, 764 .
AMA StyleEugenia Mariana Tudor, Marius Catalin Barbu, Alexander Petutschnigg, Roman Réh, Ľuboš Krišťák. Analysis of Larch-Bark Capacity for Formaldehyde Removal in Wood Adhesives. International Journal of Environmental Research and Public Health. 2020; 17 (3):764.
Chicago/Turabian StyleEugenia Mariana Tudor; Marius Catalin Barbu; Alexander Petutschnigg; Roman Réh; Ľuboš Krišťák. 2020. "Analysis of Larch-Bark Capacity for Formaldehyde Removal in Wood Adhesives." International Journal of Environmental Research and Public Health 17, no. 3: 764.
The research on population shows that the count of overweight people has been constantly growing. Therefore, designing and modifying utility items, e.g., furniture should be brought into focus. Indeed, furniture function and safety is associated with the weight of a user. Current processes and standards dealing with the design of seating furniture do not meet the requirements of overweight users. The research is aimed at designing flexible chairs consisting of lamellae using the finite element method (FEM). Three types of glued lamellae based on wood with different number of layers and thickness were made and subsequently, their mechanical properties were tested. Values for modulus of elasticity and modulus of rupture were used to determine stress and deformation applying the FEM method for modelling flexible chairs. In this research, the methodology for evaluating the ultimate state of flexible chairs used to analyse deformation and stability was defined. The analysis confirms that several designed constructions meet the requirements of actual standards (valid for the weight of a user up to 110 kg) but fail to meet the requirements for weight gain of a population.
Nadežda Langová; Roman Réh; Rastislav Igaz; Ľuboš Krišťák; Miloš Hitka; Pavol Joščák. Construction of Wood-Based Lamella for Increased Load on Seating Furniture. Forests 2019, 10, 525 .
AMA StyleNadežda Langová, Roman Réh, Rastislav Igaz, Ľuboš Krišťák, Miloš Hitka, Pavol Joščák. Construction of Wood-Based Lamella for Increased Load on Seating Furniture. Forests. 2019; 10 (6):525.
Chicago/Turabian StyleNadežda Langová; Roman Réh; Rastislav Igaz; Ľuboš Krišťák; Miloš Hitka; Pavol Joščák. 2019. "Construction of Wood-Based Lamella for Increased Load on Seating Furniture." Forests 10, no. 6: 525.
The results of research into utilizing grinded beech bark in order to substitute commonly used fillers in urea formaldehyde (UF) adhesive mixtures to bond plywood are presented in the present study. Four test groups of plywood with various adhesive mixtures were manufactured under laboratory conditions and used for experimentation. Plywood made using the same technology, with the common filler (technical flour), was used as a reference material. Three different concentrations of grinded beech bark were used. The thermal conductivity of the fillers used, viscosity and its time dependence, homogeneity and the dispersion performance of fillers were evaluated in the analysis of adhesive mixture. The time necessary for heating up the material during the pressing process was a further tested parameter. The produced plywood was analyzed in terms of its modulus of elasticity, bending strength, perpendicular tensile strength and free formaldehyde emissions. Following the research results, beech bark can be characterized as an ecologically friendly alternative to technical flour, shortening the time of pressing by up to 27%. At the same time, in terms of the statistics, the mechanical properties and stability of the material changed insignificantly, and the formaldehyde emissions reduced significantly, by up to 74%. The utilization of bark was in compliance with long-term sustainability, resulting in a decrease in the environmental impact of waste generated during the wood processing.
Roman Réh; Rastislav Igaz; Ľuboš Krišťák; Ivan Ružiak; Milada Gajtanska; Monika Božíková; Martin Kučerka. Functionality of Beech Bark in Adhesive Mixtures Used in Plywood and Its Effect on the Stability Associated with Material Systems. Materials 2019, 12, 1298 .
AMA StyleRoman Réh, Rastislav Igaz, Ľuboš Krišťák, Ivan Ružiak, Milada Gajtanska, Monika Božíková, Martin Kučerka. Functionality of Beech Bark in Adhesive Mixtures Used in Plywood and Its Effect on the Stability Associated with Material Systems. Materials. 2019; 12 (8):1298.
Chicago/Turabian StyleRoman Réh; Rastislav Igaz; Ľuboš Krišťák; Ivan Ružiak; Milada Gajtanska; Monika Božíková; Martin Kučerka. 2019. "Functionality of Beech Bark in Adhesive Mixtures Used in Plywood and Its Effect on the Stability Associated with Material Systems." Materials 12, no. 8: 1298.
Good quality sleep is a prerequisite for regenerating the human body, hence, beds should be optimized for specific group of users, taking into consideration their size or age. Current research studies show similar trends in adult populations around the world, where increases in height as well as in weight can be observed. Not only the ergonomics but also the safety of beds, which is determined by the quality and dimensions of structural elements, must be taken into account in bed design. Designing the structural elements for users with a high body weight is presented in the paper. The properties of a bed’s structural elements, which ensure comfort as well as the safety of a bed are affected by the excess weight of users. New requirements for cross sections, suitable materials and construction of structural elements were set in accordance with the standard EN 1725:1998 [1]. Also, an analysis of stresses was done using the finite element method (FEM) and the calculation of allowable stresses related to a user weighing 150 kg. The results of our research provide complete standards and regulations associated with the safety requirements of bedroom furniture for users with a weight more than 110 kg to ensure that the manusfacture of quality products in Slovakia.
Roman Réh; Ľuboš Krišťák; Miloš Hitka; Nadežda Langová; Pavol Joščák; Miloš Čambál. Analysis to Improve the Strength of Beds Due to the Excess Weight of Users in Slovakia. Sustainability 2019, 11, 624 .
AMA StyleRoman Réh, Ľuboš Krišťák, Miloš Hitka, Nadežda Langová, Pavol Joščák, Miloš Čambál. Analysis to Improve the Strength of Beds Due to the Excess Weight of Users in Slovakia. Sustainability. 2019; 11 (3):624.
Chicago/Turabian StyleRoman Réh; Ľuboš Krišťák; Miloš Hitka; Nadežda Langová; Pavol Joščák; Miloš Čambál. 2019. "Analysis to Improve the Strength of Beds Due to the Excess Weight of Users in Slovakia." Sustainability 11, no. 3: 624.
Eugenia Mariana Tudor; Marius C. Barbu; Alexander Petutschnigg; Roman Reh. Added-value for wood bark as a coating layer for flooring tiles. Journal of Cleaner Production 2018, 170, 1354 -1360.
AMA StyleEugenia Mariana Tudor, Marius C. Barbu, Alexander Petutschnigg, Roman Reh. Added-value for wood bark as a coating layer for flooring tiles. Journal of Cleaner Production. 2018; 170 ():1354-1360.
Chicago/Turabian StyleEugenia Mariana Tudor; Marius C. Barbu; Alexander Petutschnigg; Roman Reh. 2018. "Added-value for wood bark as a coating layer for flooring tiles." Journal of Cleaner Production 170, no. : 1354-1360.
The influence of beech bark concentrations as filler in urea-formaldehyde (UF) adhesives was investigated relative to the composite forming process and selected properties of final 5-layer beech plywood. Beech bark was used as filler to lower the wood processing waste production and decrease formaldehyde emissions. A combination of UF adhesives filled with different beech bark concentrations as the adhesive was used. Three different concentrations of beech bark, 15 wt.%, 20 wt.%, and 25 wt.% were used in the experiment. Urea-formaldehyde adhesive filled with 20 wt.% technical flour was used as a reference sample. The effect of the filler was studied via its temperature profile during pressing, mechanical properties in bending, water absorption, thickness swelling, and formaldehyde emissions after pressing. The time needed to reach the temperature between the beech veneers, at least 105 °C, which was equal to the final temperature filler-adhesive-wood matrix cross-linking, was also investigated during the pressing process. The measurements of the free formaldehyde emissions showed that for samples with non-zero bark concentrations there was a decrease of formaldehyde emissions by at least 46%.
Ivan Ružiak; Rastislav Igaz; Ľuboš Krišťák; Roman Reh; Jozef Mitterpach; Alena Očkajová; Martin Kučerka. Influence of Urea-formaldehyde Adhesive Modification with Beech Bark on Chosen Properties of Plywood. BioResources 2017, 12, 1 .
AMA StyleIvan Ružiak, Rastislav Igaz, Ľuboš Krišťák, Roman Reh, Jozef Mitterpach, Alena Očkajová, Martin Kučerka. Influence of Urea-formaldehyde Adhesive Modification with Beech Bark on Chosen Properties of Plywood. BioResources. 2017; 12 (2):1.
Chicago/Turabian StyleIvan Ružiak; Rastislav Igaz; Ľuboš Krišťák; Roman Reh; Jozef Mitterpach; Alena Očkajová; Martin Kučerka. 2017. "Influence of Urea-formaldehyde Adhesive Modification with Beech Bark on Chosen Properties of Plywood." BioResources 12, no. 2: 1.
It would seem that with appropriate treatment almost any agricultural residue may be used as a suitable raw material for the wood-based panels like particle- and fiberboard production. The literature on wood-ligno-cellulose plant composite boards highlights steady interest for the design of new structures and technologies towards products for special applications with higher physical-mechanical properties at relatively low prices. Experimental studies have revealed particular aspects related to the structural composition of ligno-cellulose materials, such as the ratio between the different composing elements, their compatibility, and the types and characteristics of the used resins. Various technologies have been developed for designing and processing composite materials by pressing, extrusion, airflow forming, dry, half-dry, and wet processes, including thermal, chemical, thermo-chemical, thermo-chemo-mechanical treatments, etc. Researchers have undertaken to determine the manufacturing parameters and the physical-mechanical properties of the composite boards and to compare them with the standard PB, MDF, HB, SB made from single-raw material (wood). A great emphasis is placed on the processability of the ligno-cellulose composite boards by classical methods, by modified manufacturing processes, on the types of tools and processing equipment, the automation of the manufacturing technologies, the specific labor conditions, etc. The combinations of wood and plant fibers are successful, since there is obvious compatibility between the macro- and microscopic structures, their chemical composition, and the relatively low manufacturing costs and high performances, as compared to synthetic fiber-based composite materials.
Marius C. Barbu; Roman Reh; Ayfer Dönmez Çavdar. Non-Wood Lignocellulosic Composites. Materials Science and Engineering 2017, 947 -977.
AMA StyleMarius C. Barbu, Roman Reh, Ayfer Dönmez Çavdar. Non-Wood Lignocellulosic Composites. Materials Science and Engineering. 2017; ():947-977.
Chicago/Turabian StyleMarius C. Barbu; Roman Reh; Ayfer Dönmez Çavdar. 2017. "Non-Wood Lignocellulosic Composites." Materials Science and Engineering , no. : 947-977.
Wood composites are made from various wood or ligno-cellulosic non-wood materials (shape and origin) that are bonded together using either natural bonding or synthetic resin (e.g. thermoplastic or duroplastic polymers), or organic- (e.g. plastics)/inorganic-binder (e.g. cement). This product mix ranges from panel products (e.g., plywood, particleboard, strandboard, or fiberboard) to engineered timber substitutes (e.g., laminated veneer lumber or structural composite lumber). These composites are used for a number of structural and nonstructural applications in product lines ranging from interior to exterior applications (e.g. furniture and architectural trim in buildings). Wood composite materials can be engineered to meet a range of specific properties. When wood materials and processing variables are properly selected, the result can provide high performance and reliable service. Laminated composites consist of wood veneers bonded with a resin-binder and fabricated with either parallel- (e.g. Laminated Veneer Lumber with higher performance properties parallel to grain) or cross-banded veneers (e.g. plywood, homogenous and with higher dimensional stability). Particle-, strand-, or fiberboard composites are normally classified by density (high, medium, low) and element size. Each is made with a dry woody element, except for fiberboard, which can be made by either dry or wet processes. Hybrid composites based on wood wool, particles, and floor mixed with cement or gypsum are used in construction proving high weathering and fire resistance in construction. The mixture with plastics (PP or PE) and wood floor open a new generation of injected or molded Wood Plastic Composites (WPC), which are able to substitute plastics for some utilizations. In addition, sandwich panels with light core made from plastic foams or honeycomb papers are used in the furniture industry.
Marius C. Barbu; Roman Réh; Mark Irle. Wood-Based Composites. Materials Science and Engineering 2017, 1038 -1074.
AMA StyleMarius C. Barbu, Roman Réh, Mark Irle. Wood-Based Composites. Materials Science and Engineering. 2017; ():1038-1074.
Chicago/Turabian StyleMarius C. Barbu; Roman Réh; Mark Irle. 2017. "Wood-Based Composites." Materials Science and Engineering , no. : 1038-1074.