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Prof. Dr. Ľuboš Krišťák
Technical University in Zvolen, Slovakia, Department of Physics, Electrical Engineering and Applied Mechanics

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0 wood composites
0 Physical properties of wood
0 mechanical properties of wood
0 wood machining
0 wood dust

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wood composites
wood dust
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Journal article
Published: 27 August 2021 in Materials
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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.

ACS Style

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 Style

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 (17):4875.

Chicago/Turabian Style

Pavlo 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.

Journal article
Published: 18 August 2021 in Polymers
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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.

ACS Style

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 Style

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 (16):2775.

Chicago/Turabian Style

Petar 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.

Journal article
Published: 05 August 2021 in Forests
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The aim of this paper was to determine the particle size composition of wood dust emission from CNC milling of natural wood and medium-density fiberboard (MDF) and evaluate the associated occupational exposure risks. The paper is focused on some of the most commonly used materials in the woodworking and furniture industry, i.e., solid wood (beech, oak, and spruce) and composite materials (MDF panels). In addition to the influence of the machined material, the effect of the technical-technological parameters, namely, feed speed and depth of cut on the particle size distribution, was also investigated. The selected values of the technical-technological parameters used in this study followed the common work practice in small wood processing companies. The particle size distribution was evaluated by using sieve analysis of samples from the total mass of collected wood dust. The results demonstrated that machining of natural wood is characterized mostly by the formation of coarse dust fractions (2 mm–1 mm sieves), whilst the processing of MDF was associated with generation of fine dust fractions with a size below 100 μm. The results obtained can be used for optimizing the technological programs of CNC milling machines, thus, reducing the occupational exposure to harmful wood dust emissions in the wood-processing industry.

ACS Style

Richard Kminiak; Martin Kučerka; Lubos Kristak; Roman Reh; Petar Antov; Alena Očkajová; Tomasz Rogoziński; Marta Pędzik. Granulometric Characterization of Wood Dust Emission from CNC Machining of Natural Wood and Medium Density Fiberboard. Forests 2021, 12, 1039 .

AMA Style

Richard Kminiak, Martin Kučerka, Lubos Kristak, Roman Reh, Petar Antov, Alena Očkajová, Tomasz Rogoziński, Marta Pędzik. Granulometric Characterization of Wood Dust Emission from CNC Machining of Natural Wood and Medium Density Fiberboard. Forests. 2021; 12 (8):1039.

Chicago/Turabian Style

Richard Kminiak; Martin Kučerka; Lubos Kristak; Roman Reh; Petar Antov; Alena Očkajová; Tomasz Rogoziński; Marta Pędzik. 2021. "Granulometric Characterization of Wood Dust Emission from CNC Machining of Natural Wood and Medium Density Fiberboard." Forests 12, no. 8: 1039.

Editorial
Published: 31 July 2021 in Polymers
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Wood and wood-based composites are key engineering materials that can be successfully designed and manufactured with predetermined exploitation properties, making them suitable for a wide range of applications and end uses

ACS Style

Lubos Kristak; Ivan Kubovský; Roman Réh. New Challenges in Wood and Wood-Based Materials. Polymers 2021, 13, 2538 .

AMA Style

Lubos Kristak, Ivan Kubovský, Roman Réh. New Challenges in Wood and Wood-Based Materials. Polymers. 2021; 13 (15):2538.

Chicago/Turabian Style

Lubos Kristak; Ivan Kubovský; Roman Réh. 2021. "New Challenges in Wood and Wood-Based Materials." Polymers 13, no. 15: 2538.

Journal article
Published: 18 July 2021 in Applied Sciences
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Wood dust generated during woodworking—particularly from hardwood species during sanding—poses a health and safety hazard to workers in the wood industry. This study aimed to determine the particle-size distribution of selected hardwood species and the content of fine particles in dust created during machine sanding, which pose the highest health and safety hazards in the woodworking industry. Six hardwood species were studied: black alder, European ash, common walnut, pedunculate oak, hornbeam, and European beech. The sieve analysis method was used to determine the particle-size distribution and article mean arithmetic particle diameter, and laser diffraction analysis was used to determine the finest particle content. Two size ranges were assumed: <2.5 μm and <10 μm. Beech dust had the smallest mean particle diameter. Dust from wood species used in the test had similar contents of fine fractions of particles. The average content of particles smaller than 2.5 µm in wood dust from the tested hardwood species did not exceed 1.9%. In terms of occupational exposure to wood dust, machine sanding conditions of hardwoods should be properly adjusted to limit the formation of large amounts of dust.

ACS Style

Marta Pędzik; Tomasz Rogoziński; Jerzy Majka; Kinga Stuper-Szablewska; Petar Antov; Lubos Kristak; Richard Kminiak; Martin Kučerka. Fine Dust Creation during Hardwood Machine Sanding. Applied Sciences 2021, 11, 6602 .

AMA Style

Marta Pędzik, Tomasz Rogoziński, Jerzy Majka, Kinga Stuper-Szablewska, Petar Antov, Lubos Kristak, Richard Kminiak, Martin Kučerka. Fine Dust Creation during Hardwood Machine Sanding. Applied Sciences. 2021; 11 (14):6602.

Chicago/Turabian Style

Marta Pędzik; Tomasz Rogoziński; Jerzy Majka; Kinga Stuper-Szablewska; Petar Antov; Lubos Kristak; Richard Kminiak; Martin Kučerka. 2021. "Fine Dust Creation during Hardwood Machine Sanding." Applied Sciences 11, no. 14: 6602.

Journal article
Published: 12 July 2021 in Polymers
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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.

ACS Style

Lubos Kristak; Ivan Ruziak; Eugenia Tudor; Marius Barbu; Günther Kain; Roman Reh. Thermophysical Properties of Larch Bark Composite Panels. Polymers 2021, 13, 2287 .

AMA Style

Lubos 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 Style

Lubos Kristak; Ivan Ruziak; Eugenia Tudor; Marius Barbu; Günther Kain; Roman Reh. 2021. "Thermophysical Properties of Larch Bark Composite Panels." Polymers 13, no. 14: 2287.

Journal article
Published: 07 July 2021 in Forests
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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.

ACS Style

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 Style

Eugenia 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 Style

Eugenia 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.

Editorial
Published: 13 April 2021 in Applied Sciences
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Wood composites are the key material for a number of structural and non-structural applications for interior and exterior purposes, such as furniture, construction, floorings, windows and doors, etc

ACS Style

Ľuboš Krišťák; Roman Réh. Application of Wood Composites. Applied Sciences 2021, 11, 3479 .

AMA Style

Ľuboš Krišťák, Roman Réh. Application of Wood Composites. Applied Sciences. 2021; 11 (8):3479.

Chicago/Turabian Style

Ľuboš Krišťák; Roman Réh. 2021. "Application of Wood Composites." Applied Sciences 11, no. 8: 3479.

Journal article
Published: 02 April 2021 in Polymers
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Planer shavings (PS) are side-products generated during the processing of solid wood, typically used for heating, packaging, or insulation purposes. PS has been used for decades in particleboard manufacture, particularly in the core layer. The aim of this research is to investigate the use of PS with a length over 4 mm in low-density one-layer particleboard manufacturing with a thickness of 10 mm, as an option to reduce the raw material demand for wood-based panels. Correlations towards the mechanical properties of the particleboards, fabricated at a density of 475 kg/m3, could be drawn by analyzing the effects of different urea-formaldehyde adhesive contents (6%, 9%, and 12%). Two methods of adhesive application (pouring and spraying) and two types of blending of PS with adhesive (plowshare mixer and drum mixer) were investigated, with the aim that PS will have controlled resin application. The difference between the adhesive application methods was examined by analyzing the mechanical properties as an internal bond, modulus of rupture, and modulus of elasticity as well as indirectly by visualizing the adhesive distribution by adding a green pigment to the adhesive before application. PS demonstrated reduced bending properties in comparison with the EN 312 standard requirements of particleboards for internal use in dry conditions (type P2), due to the low density. The internal bond strength in the case of the particleboard without pigment application (up to 0.5 N/mm2) was higher compared to the P2 requirements (0.4 N/mm2), and significantly lower (0.15 N/mm2) in combination with the pigment (2.5% based on the board weight, compared to 0.1%, specific for such industry applications), but still superior to the values of the reference panel manufactured with wood particles.

ACS Style

Jakob Gößwald; Marius Barbu; Alexander Petutschnigg; Ľuboš Krišťák; Eugenia Tudor. Oversized Planer Shavings for the Core Layer of Lightweight Particleboard. Polymers 2021, 13, 1125 .

AMA Style

Jakob Gößwald, Marius Barbu, Alexander Petutschnigg, Ľuboš Krišťák, Eugenia Tudor. Oversized Planer Shavings for the Core Layer of Lightweight Particleboard. Polymers. 2021; 13 (7):1125.

Chicago/Turabian Style

Jakob Gößwald; Marius Barbu; Alexander Petutschnigg; Ľuboš Krišťák; Eugenia Tudor. 2021. "Oversized Planer Shavings for the Core Layer of Lightweight Particleboard." Polymers 13, no. 7: 1125.

Journal article
Published: 21 February 2021 in Polymers
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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.

ACS Style

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 Style

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 (4):639.

Chicago/Turabian Style

Petar 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.

Journal article
Published: 08 February 2021 in Polymers
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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.

ACS Style

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 Style

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 (4):511.

Chicago/Turabian Style

Roman 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.

Journal article
Published: 10 January 2021 in Polymers
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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.

ACS Style

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 Style

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 (2):220.

Chicago/Turabian Style

Petar 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.

Journal article
Published: 29 November 2020 in Polymers
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The current work deals with three dimensionally molded plywood formed parts. These are prepared in two different geometries using cut-outs and relief cuts in the areas of the highest deformation. Moreover, the effect of flax fiber reinforcement on the occurrence and position of cracks, delamination, maximum load capacity, and on the modulus of elasticity is studied. The results show that designs with cut-outs are to be preferred when molding complex geometries and that flax fiber reinforcement is a promising way of increasing load capacity and stiffness of plywood formed parts by respectively 76 and 38% on average.

ACS Style

Johannes Jorda; Günther Kain; Marius-Catalin Barbu; Matthias Haupt; Ľuboš Krišťák. Investigation of 3D-Moldability of Flax Fiber Reinforced Beech Plywood. Polymers 2020, 12, 2852 .

AMA Style

Johannes Jorda, Günther Kain, Marius-Catalin Barbu, Matthias Haupt, Ľuboš Krišťák. Investigation of 3D-Moldability of Flax Fiber Reinforced Beech Plywood. Polymers. 2020; 12 (12):2852.

Chicago/Turabian Style

Johannes Jorda; Günther Kain; Marius-Catalin Barbu; Matthias Haupt; Ľuboš Krišťák. 2020. "Investigation of 3D-Moldability of Flax Fiber Reinforced Beech Plywood." Polymers 12, no. 12: 2852.

Journal article
Published: 16 November 2020 in Applied Sciences
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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.

ACS Style

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 Style

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 (22):8113.

Chicago/Turabian Style

Ivan 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.

Journal article
Published: 17 September 2020 in Applied Sciences
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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.

ACS Style

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 Style

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 (18):6499.

Chicago/Turabian Style

Günther 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.

Journal article
Published: 12 August 2020 in Applied Sciences
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The aim of this study was to investigate the flammability of ecologically friendly, 100% natural larch and poplar bark-based panels bonded with clay. The clay acted as a fire retardant, and it improved the fire resistance of the boards by 12–15% for the surface and 27–39% for the edge of the testing specimens. The thermal conductivity was also analyzed. Although the panels had a density ranging from 600 to 900 kg/m3, thermal conductivity for the panel with a density of 600 kg/m3 was excellent, and it was comparable to lightweight insulation panels with much lower densities. Besides that, the advantage of the bark clay boards, as an insulation material, is mostly in an accumulative capacity similar to wood cement boards, and it can significantly improve the climatic stability of indoor spaces that have low ventilation rates. Bark boards with clay, similar to wood cement composites (wood wool cement composites and wood particle cement composites), have low mechanical properties and elasticity. Therefore, there their use is limited to non-structural paneling applications. These ecologically friendly, 100% natural and recyclable composites can be mostly used with respect to their thermal insulation, acoustics and fire resistance properties.

ACS Style

Eugenia Mariana Tudor; Christoph Scheriau; Marius Catalin Barbu; Roman Réh; Ľuboš Krišťák; Thomas Schnabel. Enhanced Resistance to Fire of the Bark-Based Panels Bonded with Clay. Applied Sciences 2020, 10, 5594 .

AMA Style

Eugenia Mariana Tudor, Christoph Scheriau, Marius Catalin Barbu, Roman Réh, Ľuboš Krišťák, Thomas Schnabel. Enhanced Resistance to Fire of the Bark-Based Panels Bonded with Clay. Applied Sciences. 2020; 10 (16):5594.

Chicago/Turabian Style

Eugenia Mariana Tudor; Christoph Scheriau; Marius Catalin Barbu; Roman Réh; Ľuboš Krišťák; Thomas Schnabel. 2020. "Enhanced Resistance to Fire of the Bark-Based Panels Bonded with Clay." Applied Sciences 10, no. 16: 5594.

Journal article
Published: 29 April 2020 in Polymers
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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.

ACS Style

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 Style

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 (5):1012.

Chicago/Turabian Style

Eugenia 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.

Journal article
Published: 25 February 2020 in International Journal of Environmental Research and Public Health
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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.

ACS Style

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 Style

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 (5):1478.

Chicago/Turabian Style

Alena 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.

Journal article
Published: 25 January 2020 in International Journal of Environmental Research and Public Health
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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.

ACS Style

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 Style

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 (3):764.

Chicago/Turabian Style

Eugenia 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.

Journal article
Published: 11 December 2019 in BioResources
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The quality of milled surface medium-density fibreboards (MDF) and the effect of the wrong milling direction during the process of automatic milling in real conditions in practice (production machine, production tool, and material) are presented in the paper. Moreover, the effect of the double vs. single bladed milling cutter on the final surface quality with the simultaneous changes in individual parameters of feed rate, thickness of the removed layer, and cutting direction was investigated. The MDF was separated using the strategy “one per pass“ with required cutting direction (climb or conventional) and the required thick strips cutting off (4 mm to 16+ mm) at a constant operation speed of the milling cutter (n = 20000 min−1) and a changing feed rate from vf = 1 m/min−1 to vf = 5 m/min−1. The use of a multi-bladed milling cutter resulted in the higher quality of the milled surface in all cases (change in feed rate, thickness of removed layer, and cutting direction). The effect of the wrong milling direction during automatic milling was observed only for a single-bladed milling cutter used. An increase in surface roughness (Ra) occurred; therefore, using the double-bladed milling cutter, which was not associated with an increase in surface roughness, is recommended.

ACS Style

Richard Kminiak; Mikuláš Siklienka; Rastislav Igaz; Ľuboš Krišťák; Tomáš Gergeľ; Miroslav Němec; Roman Réh; Alena Očkajová; Martin Kučerka. Effect of cutting conditions on quality of milled surface of medium-density fibreboards. BioResources 2019, 15, 1 .

AMA Style

Richard Kminiak, Mikuláš Siklienka, Rastislav Igaz, Ľuboš Krišťák, Tomáš Gergeľ, Miroslav Němec, Roman Réh, Alena Očkajová, Martin Kučerka. Effect of cutting conditions on quality of milled surface of medium-density fibreboards. BioResources. 2019; 15 (1):1.

Chicago/Turabian Style

Richard Kminiak; Mikuláš Siklienka; Rastislav Igaz; Ľuboš Krišťák; Tomáš Gergeľ; Miroslav Němec; Roman Réh; Alena Očkajová; Martin Kučerka. 2019. "Effect of cutting conditions on quality of milled surface of medium-density fibreboards." BioResources 15, no. 1: 1.