173 results on '"Medved, Sergej"'
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2. Processing and functional assessment of anisotropic cellulose nanofibril/Alolt/sodium silicate: based aerogels as flame retardant thermal insulators
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Gorgieva, Selestina, Jančič, Urška, Hribernik, Silvo, Fakin, Darinka, Stana Kleinschek, Karin, Medved, Sergej, Fakin, Tomaž, and Božič, Mojca
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- 2020
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- View/download PDF
3. Kompoziti iz skorje: nova gozdarsko-lesarska vrednostna veriga.
- Author
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MEDVED, Sergej, VILMAN, Gregor, TAJHER, Urban, SEVER, Mark, and ANTONOVIĆ, Alan
- Abstract
Copyright of Gozdarski Vestnik is the property of Federation of Forestry Associations of Slovenia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2023
4. Properties and Emissions of Three-Layer Particleboards Manufactured with Mixtures of Wood Chips and Partially Liquefied Bark
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Jiang, Wen, primary, Adamopoulos, Stergios, additional, Hosseinpourpia, Reza, additional, Walther, Thomas, additional, and Medved, Sergej, additional
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- 2023
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5. Tannin-caprolactam and Tannin-PEG formulations as outdoor wood preservatives: weathering properties
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Tondi, Gianluca, Hu, Jinbo, Rizzo, Filippo, Buh, Janez, Medved, Sergej, Petutschnigg, Alexander, and Thevenon, Marie-France
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- 2017
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6. MECHANICAL TESTING OF LAMINATED COMPOSITE MATERIALS FOR PROSTHETIC SOCKETS
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Bombek, Matic, primary, Vesenjak, Uroš, additional, Pisek, Marko, additional, Vidmar, Gaj, additional, Knez, Sašo, additional, and Medved, Sergej, additional
- Published
- 2021
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7. Thermal insulation panels from cellulosic fibres
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Medved, Sergej, Lesar, Bostjan, Tudor, Eugenia Mariana, and Humar, Miha
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Insulation (Heat) -- Analysis ,Cellulose fibers -- Analysis ,Insulating materials -- Analysis ,Business ,Forest products industry - Abstract
ABSTRACT Recycling of paper is a relatively old but important process. During breakdown of recycled paper cellulosic fibres with different morphology (size) are generated. An important aspect that was considered [...]
- Published
- 2015
8. Particleboards with partially liquefied bark of different particle sizes
- Author
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Jiang, Wen, Adamopoulos, Stergios, Petric, Marko, Sernek, Milan, and Medved, Sergej
- Subjects
Wood Science ,complex mixtures - Abstract
This paper presents a novel method of partially liquefying bark sawmilling waste for use in making particleboards. Maritime pine (Pinus pinaster Ait.) bark of different particle sizes (fine, medium, coarse, and mixed) was partially liquefied in the presence of ethylene glycol as a solvent and sulphuric acid as a catalyst at 180 degrees C for 30 minutes. Single-layer particleboards were prepared by mixing partially liquefied bark (PLB) and wood chips at a ratio of 0.25 with no adhesives (group A) and at ratios of 0.25 or 0.1 with melamine-urea-formaldehyde (MUF) adhesives for additional bonding (groups B and C respectively). Mechanical and physical properties of the particleboards were tested according to European standards. The results showed that the boards in group A had lower densities, inferior mechanical properties and higher moisture content than those in groups B and C. Bark particle size had a significant effect on the mechanical properties of particleboards within each group. Additional MUF bonding and avoidance of coarse bark particles had a positive effect on mechanical properties. The thickness swelling (TS) and water absorption (WA) values of MUF-bonded boards were lower than those of boards without MUF, and greater addition of PLB produced particleboards with better water resistance. Bark particle size was not as critical for TS and WA as for mechanical properties. The overall results suggested using a bark particle size of < 2 mm for further studies.
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- 2021
9. Hardness and density profile of surface densified and thermally modified Scots pine in relation to degree of densification
- Author
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Rautkari, Lauri, Laine, Kristiina, Kutnar, Andreja, Medved, Sergej, and Hughes, Mark
- Published
- 2013
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10. PARTICLEBOARDS WITH PARTIALLY LIQUEFIED BARK OF DIFFERENT PARTICLE SIZES
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JIANG, Wen, primary, ADAMOPOULOS, Stergios, additional, PETRIČ, Marko, additional, ŠERNEK, Milan, additional, and MEDVED, Sergej, additional
- Published
- 2021
- Full Text
- View/download PDF
11. Thermal conductivity of different bio-based insulation materials
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Medved, Sergej, primary, Tudor, Eugenia Mariana, additional, Barbu, Marius Catalin, additional, and Young, Timothy M., additional
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- 2021
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12. On the performance of a melamine–urea–formaldehyde resin for decorative paper coatings
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Kandelbauer, Andreas, Petek, Primoz, Medved, Sergej, Pizzi, Antonio, and Teischinger, Alfred
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- 2010
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13. Influence of resin content on the surface covered with adhesive
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Medved, Sergej, primary and Grudnik, Jure, additional
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- 2021
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14. Alien Wood Species as a Resource for Wood-Plastic Composites
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Medved, Sergej, primary, Tomec, Daša Krapež, additional, Balzano, Angela, additional, and Merela, Maks, additional
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- 2020
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15. Utilization of Partially Liquefied Bark for Production of Particleboards
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Jiang, Wen, primary, Adamopoulos, Stergios, additional, Hosseinpourpia, Reza, additional, Žigon, Jure, additional, Petrič, Marko, additional, Šernek, Milan, additional, and Medved, Sergej, additional
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- 2020
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16. Processing and functional assessment of anisotropic cellulose nanofibril/Alolt/sodium silicate: based aerogels as flame retardant thermal insulators
- Author
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Gorgieva, Selestina, primary, Jančič, Urška, additional, Hribernik, Silvo, additional, Fakin, Darinka, additional, Stana Kleinschek, Karin, additional, Medved, Sergej, additional, Fakin, Tomaž, additional, and Božič, Mojca, additional
- Published
- 2019
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17. Influence of Different Wood Species Chemical Composition on the Liquefaction Properties
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Antonović, Alan, Ištvanić, Josip, Medved, Sergej, Antolović, Suzana, Stanešić, Juraj, Kukuruzović, Juraj, Đurović, Alan, Španić, Nikola, Beljo Lučić, R., Živković, V., Pirc Barčić, A., and Vlaović, Z.
- Subjects
hydroxyl number ,liquefaction degree ,residual percentage ,wood liquefaction, wood species - Abstract
This paper presents the properties characterization of liquefied different wood species according to their chemical composition. Four hardwood species namely black poplar (Populus nigra L.), beech (Fagus sylvatica), sessile oak (Quercus petraea Liebl.) and common oak (Quercus robur L.) and two softwood species namely common fir (Abies alba Mill.) and spruce (Picea abies Karst.) were liquefied via catalytic liquefaction in the reactor using glycerol solvent as liquefaction reagent under defined reaction conditions: wood/glycerol=1:5, sulfuric acid as catalyst (3 wt%) at 150 °C for 120 min. The chemical composition analysis of the same wood species was carried out for their influence on liquefaction properties. The percentage residues, liquefaction degree and hydroxyl OH- numbers were determined as liquefaction properties. According to gained results and as the main aim, it determined the most suitable wood species for the liquefaction process in terms of obtaining the best liquefaction properties. Furthermore, this reagent system was showed suitable for liquefaction of a wide variety of wood species.
- Published
- 2019
18. Chemical composition of fired Aleppo pine (Pinus halepensis Mill.) sapwood
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Antonović, Alan, Barčić, Damir, Španić, Nikola, Medved, Sergej, Stanešić, Juraj, Podvorec, Tomislav, Lozančić, Matija, Štriga, Sebastijan, Ištvanić, Josip, Župčić, Ivica, and Španić, Nikola
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Aleppo pine (Pinus halepensis Mill.) ,fired wood ,forest fires ,sapwood ,group chemical composition - Abstract
More recently in Croatia, as well as in the whole world, there are more and more issues with forest fires. After the forest fires, significant quantities of fired trees as a lignocellulosic biomass are left behind, and the question arises as to what degree they are chemically degraded or whether they still possess all the properties for further application in mechanical or chemical processing. According to that, the main aim of this study was to research the impact of low ground fire and high fire of the treetops on the Aleppo pine (Pinus halepensis Mill.) sapwood group chemical composition. The study was carried out by determining the group chemical composition of fired sapwood and nonfired for comparison with the fired, by sampling the rings at the height of the trees 0 m, 2 m 4 m. In addition, research results on group chemical composition of nonfired and fired Aleppo pine wood bark and sapwood from previous studies were used for comparison with sapwood from this study. The obtained results shows that the forest fires did not have any effect on overall Aleppo pine sapwood, where the fired wood bark take over all the damage caused by the high temperature during the forest fire.
- Published
- 2018
19. Formaldehyde barrier efficiency of melamine impregnated paper and melamine edge-banding tape surfaced particleboard and MDF: Učinkovitost papirja, impregniranega z melaminsko smolo, in melaminskega robnega traku pri oblaganju ivernih plošč in MDF-plošč z vidika zmanjšanja emisije formaldehida
- Author
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Forštnarič, Jernej and Medved, Sergej
- Abstract
Particleboard and MDF are the most usable materials for furniture production, where emission of formaldehyde should be as low as possible. In order to improve aesthetic properties of particleboard and MDF they are covered with appropriate surfacing material. In most cases, melamine impregnated paper is used for face layers. But covering faces should be accompanied with covered edges, as due to low density of core layer formaldehyde much more easily emits from edges than from faces. The presented research shows differences in formaldehyde emission rate at unsurfaced and surfaced MDF and particleboard. For face layer, melamine impregnated papers with grammages of 130 g/m2 and 200 g/m2 were used, while for covering edges, melamine edge-banding tape was applied. In the research it was determined that higher barrier effect was achieved when impregnated paper with a grammage of 200 g/m2 was used. When surface was completely covered with impregnated paper and melamine edge-band tape, formaldehyde emission was lowered by between 83 % and 94 %. Iverne in MDF-plošče so najpogosteje uporabljen material za izdelavo pohištva, kjer se zahteva čim nižja emisija formaldehida. MDF- in iverne plošče se s ciljem doseganja želenih estetskih karakteristik površinsko obdelajo z ustreznimi materiali. Največkrat so to papirji, impregnirani z melaminsko smolo. Samo oblaganje ploskve pa z vidika zmanjšanja emisije formaldehida ni zadostno, saj formaldehid bistveno laže prehaja skozi rob, kar posledično pomeni, da je treba obdelati oz. zapreti tudi robove. V predstavljeni raziskavi smo iverne in MDF- plošče obložili z impregniranim papirjem gramature 130 g/m2 in 200 g/m2, robove pa zaprli z melaminskim robnim trakom. Efektivnejša zaščita proti emisiji formaldehida je bila dosežena z uporabo impregniranega papirja gramature 200 g/m2. V primeru, da so bili zaprti tako robovi plošč kakor tudi ploskve, se je emisija formaldehida zmanjšala med 83 % in 94 %.
- Published
- 2018
20. Effect of Pine (Pinus Sylvestris) Bark Dust on Particleboard Thickness Swelling and Internal Bond
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Medved, Sergej, primary, Tudor, Eugenia Mariana, additional, Barbu, Marius Catalin, additional, Jambreković, Vladimir, additional, and Španić, Nikola, additional
- Published
- 2019
- Full Text
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21. Influence of Natural Fillers on Thermal and Mechanical Properties and Surface Morphology of Cellulose Acetate-Based Biocomposites
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Španić, Nikola, primary, Jambreković, Vladimir, additional, Šernek, Milan, additional, and Medved, Sergej, additional
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- 2019
- Full Text
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22. The dynamics of thickness swelling and bond strength loss of different wood-based panels at exposure to humid climate and immersion into water
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Medved, Sergej, primary, Žgajner, Damjan, additional, and Antonović, Alan, additional
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- 2019
- Full Text
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23. Alien Wood Species as a Resource for Wood-Plastic Composites.
- Author
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Medved, Sergej, Tomec, Daša Krapež, Balzano, Angela, and Merela, Maks
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INTRODUCED species ,HARDWOODS ,MALEIC anhydride ,INTRODUCED plants ,SCANNING electron microscopy ,FLEXURAL strength - Abstract
Since invasive alien species are one of the main causes of biodiversity loss in the region and thus of changes in ecosystem services, it is important to find the best possible solution for their removal from nature and the best practice for their usability. The aim of the study was to investigate their properties as components of wood-plastic composites and to investigate the properties of the wood-plastic composites produced. The overall objective was to test the potential of available alien plant species as raw material for the manufacture of products. This would contribute to sustainability and give them a better chance of ending their life cycle. One of the possible solutions on a large scale is to use alien wood species for the production of wood plastic composites (WPC). Five invasive alien hardwood species have been used in combination with polyethylene powder (PE) and maleic anhydride grafted polyethylene (MAPE) to produce various flat pressed WPC boards. Microstructural analyses (confocal laser scanning microscopy and scanning electron microscopy) and mechanical tests (flexural strength, tensile strength) were performed. Furthermore, measurements of density, thickness swelling, water absorption and dimensional stability during heating and cooling were carried out. Comparisons were made between the properties of six WPC boards (five alien wood species and mixed boards). The results showed that the differences between different invasive alien wood species were less obvious in mechanical properties, while the differences in sorption properties and dimensional stability were more significant. The analyses of the WPC structure showed a good penetration of the polymer into the lumens of the wood cells and a fine internal structure without voids. These are crucial conditions to obtain a good, mechanically strong and water-resistant material. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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24. PARTICLEBOARDS WITH PARTIALLY LIQUEFIED BARK OF DIFFERENT PARTICLE SIZES.
- Author
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Wen JIANG, ADAMOPOULOS, Stergios, PETRIČ, Marko, ŠERNEK, Milan, and MEDVED, Sergej
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PARTICLE board ,CLUSTER pine ,WOOD chips ,ACID catalysts ,ETHYLENE glycol ,SULFURIC acid ,CINNAMON - Abstract
This paper presents a novel method of partially liquefying bark sawmilling waste for use in making particleboards. Maritime pine (Pinus pinaster Ait.) bark of different particle sizes (fine, medium, coarse, and mixed) was partially liquefied in the presence of ethylene glycol as a solvent and sulphuric acid as a catalyst at 180°C for 30 minutes. Single-layer particleboards were prepared by mixing partially liquefied bark (PLB) and wood chips at a ratio of 0.25 with no adhesives (group A) and at ratios of 0.25 or 0.1 with melamine-urea-formaldehyde (MUF) adhesives for additional bonding (groups B and C respectively). Mechanical and physical properties of the particleboards were tested according to European standards. The results showed that the boards in group A had lower densities, inferior mechanical properties and higher moisture content than those in groups B and C. Bark particle size had a significant effect on the mechanical properties of particleboards within each group. Additional MUF bonding and avoidance of coarse bark particles had a positive effect on mechanical properties. The thickness swelling (TS) and water absorption (WA) values of MUF-bonded boards were lower than those of boards without MUF, and greater addition of PLB produced particleboards with better water resistance. Bark particle size was not as critical for TS and WA as for mechanical properties. The overall results suggested using a bark particle size of < 2 mm for further studies. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
25. Ugotavljanje prostega formaldehida v lesnih tvorivih
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Gornik Bučar, Dominika and Medved, Sergej
- Subjects
vsebnost prostega formaldehida ,metoda komore ,udc:630 ,formaldehid ,wood-based material ,lesno tvorivo ,perforatorska metoda ,formaldehyde ,lesni proizvod ,free formaldehyde release ,perforator method ,chamber method - Abstract
Koli~ina prostega formaldehida v lesnih proizvodih je kljub nizkim vrednostim {e vedno predmet stalnega nadzora in tudi predmet novih raziskav. Kljub {tevilnim razvitim in tudi uporabljenim metodam danes {e ne obstaja univerzalna metoda, s katero bi z najve~jo zanesljivostjo ugotovili koli~ino vsebovanega prostega formaldehida v lesnih proizvodih. V razli~nih de`elah so uporabljajo razli~ne standardizirane metode. Korelacije med nekaterimi od njih{e niso znane. V prispevku smo ugotavljali vsebnost postega formaldehida vivernih plo{~ah po perforatorski metodi, s ciljem dolo~itve korelacije med jodometri~no titracijo in acetilacetonsko metodo. Ker na koli~ino spo{~enega prostega formaldehida vpliva tudi struktura materiala, smo ugotavljali tudi vpliv sestave iverne plo{~e na koli~ino oddanega formaldehida. Korelacija med jodometri~no titracijo in acetilacetonsko metodo je dobra (R2= 0,8265). Sestava iverne plo{~e, pri ~emer smo se omejili na razmerje med srednjim in zunanjima slojema iverne plo{~e, vpliva na koli~ino oddanega formaldehida. The quantity of free formaldehyde in wood products in spite of low values is still the subject of constant supervision and also the subject of new investigations. Despite numerous methods developed and in use, there is, presently, still no universal method by means by which the quantity of free formaldehyde release in wood products can be established with certainty. In the various countries, various standardised methods are in use. The correlations among some of them are still unknown. In the article we determined the content of released free formaldehyde in particleboards according to the perforator method with the objective to determine the correlation between the iodimetric titration and acetylacetone method. Becausethe quantity of released formaldehyde is also affected by the structureof the material, we also tried to establish the influence of the composition of a chipboard on the quantity of released formaldehyde. The correlation between the iodimetric titration and acetylacetone method is good (R2 = 0.8265). The composition of a chipboard (where we limited ourselves to the ratio between the middle and external layers of the particleboard) has influence on the quantity of released formaldehyde.
- Published
- 2017
26. The Forest Fires Impact on Bark Chemical Composition of the Aleppo Pine (Pinus halepensis Mill.)
- Author
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Antonović, Alan, Barčić, Damir, Ištvanić, Josip, Medved, Sergej, Podvorec, Tomislav, Stanešić, Juraj, and Trposki, Z.
- Subjects
Aleppo pine (Pinus halepensis Mill.) ,Bark group chemical composition ,Forest fires ,Nonburned wood ,Burned wood - Abstract
Forest fires occur with uncontrolled fire in the forests. They are causing great damage, which depends on the age of the forest, the tree species, the vegetation and the type of fire and its intensity, which are less common with natural causes and most often by human activity. In the Republic of Croatia fires occur most commonly in Dalmatia, the islands and the Dalmatian Zagora. Since in the mentioned areas after the fire, significant quantities of fire burned trees have been left behind, the question arises as to what degree they are chemically degraded or whether they still possess all the properties for further application in mechanical or chemical processing. The aim of this paper was to research the group chemical composition and CHNS/O of the Aleppo pine (Pinus halepensis Mill.) bark before and after the impact of low ground fire and high fire of the treetops at the height of the trees of 0, 2 and 4 m. The obtained results showed significant differences in the group chemical composition, as well as in CHNS/O of the bark between nonburned and burned wood resulting from the direct contact of the mentioned fire with the bark.
- Published
- 2017
27. Bark as a Formaldehyde Scavenger
- Author
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Medved, Sergej, Antonović, Alan, and Barbu, Marius Catalin
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Pine bark ,Formaldehyde scavenger - Abstract
Bark is much underutilized material. The majority of bark is us as fuel and for landscaping there are still significant amounts of bark that remains unused, hence creating a problem when disposed. Due to dust like shape/size bark is not suitable or desired constituent for particleboard production. One of possible use of bark is related to its chemical compositions, namely due to the phenolic like components, bark can be used as formaldehyde scavenger. The aim of paper is to present the usability of bark dust and bark extract as particleboard formaldehyde scavenger. Pine (Pinus sp.) bark was chipped in laboratory conditions. For extraction hot water extraction was used. Bark dust was added to melamine-urea-formaldehyde resin and to particles prior to blending, while bark extract was sprayed over particles prior to blending. Hand formed mat was pressed at usual conditions (temperature 200° C, 3 N/mm2 pressure). The formaldehyde emission/content was determined by Perforator method (SIST EN 12460-5), by gas analysis (SIST EN 12460-3) and by Flask method (SIST EN 717-3). The experiment showed that addition of bark positively influences formaldehyde content/emission.
- Published
- 2017
28. Vpliv zrnatosti brusnega papirja na emisijo formaldehida iz ivernih plošč: The impact of sandpaper grit size on formaldehyde emission from particleboards
- Author
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Krajšek, Gregor and Medved, Sergej
- Abstract
Sanding is an important stage of wood-based panel production, where the primary goal is to achieve a desired thickness as well as appropriate smoothness of the surface. With sanding, the emission of formaldehyde can be influenced especially by the selection of sanding paper grit size. The aim of this paper is to present how the grit size of selected sanding paper affects formaldehyde emission of three-layer particleboard. For this purpose we selected 16 mm thick particleboard for furniture use. Sanding paper with grit sizes of 40, 80 and 120 was used for particleboard sanding. Formaldehyde emission was determined by the gas analysis method (SIST EN 717-2). The findings indicate that formaldehyde emission decreases with increasing grit size of sandpaper used in the process. Brušenje je pomembna stopnja proizvodnje različnih lesnih ploščnih kompozitov. Njegov primarni namen je doseganje želene debeline in primerne gladkosti površine. Z brušenjem oz. izbiro zrnatosti brusnega papirja pa lahko vplivamo tudi na emisijo formaldehida. Da bi ugotovili vpliv zrnatosti uporabljenega brusnega papirja na emisijo formaldehida, smo iverne plošče brusili s papirji različne zrnatosti. Uporabili smo iverno ploščo debeline 16 mm, ki je namenjena za pohištveno rabo. Za brušenje smo uporabili brusni papir zrnatosti 40, 80 in 120. Emisijo formaldehida smo določili po plinski metod
- Published
- 2017
29. CREEP BEHAVIOUR OF PARTICLE-BASED PANELS AND ITS RELATION TOWARDS DENSITY PROFILE.
- Author
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MEDVED, Sergej, JAMBREKOVIĆ, Vladimir, TUDOR, Eugenia Mariana, and BARBU, Marius Catalin
- Subjects
- *
ORIENTED strand board , *STRUCTURAL panels , *PARTICLE board , *DENSITY , *BEHAVIOR - Abstract
Wood-particle-based panels are versatile materials, which can be used for packaging, furniture and construction. Their usability ranges from non-load-bearing to load-bearing purposes. Since they are used over long periods of time, it is important to know their behaviour under load over long periods. Three different particle-based panels: Oriented Strand Board - OSB type 3, P5 and P2 grade particleboard - PB) where exposed to different bending loads. The load was applied to the upper and bottom sides of the panel for 24h. The behaviour of panels was correlated to density profile. During this experiment, it was determined that deformation in bending depends on the type of composite and the side of the panel exposed to the load. The lowest deflection was observed in OSB. At 40% of maximum load, the highest deflection was determined in P5 grade PB, while at 60% of maximum load, the highest deflection was determined in P2 grade PB. The wood particle type did not play an essential role when analysing deflection, because OSB type 3 and PB grade P2 values were about 10% lower than that of the P5 structural panel. A possible reason why the deflection was 10% higher in the case of structural PB P5 could be related to the actual load applied, namely for PB P2 the load was 176 N, whereas for PB P5 the load was almost 45% higher (253 N). The deflections increased linearly corresponding to stress levels of 40% and 60% of the maximum load. [ABSTRACT FROM AUTHOR]
- Published
- 2020
30. ALIEN WOOD SPECIES FOR PARTICLEBOARDS.
- Author
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MEDVED, Sergej, VILMAN, Grega, and MERELA, Maks
- Subjects
- *
PARTICLE board , *INTRODUCED species , *BLACK locust , *AILANTHUS altissima , *BENDING strength - Abstract
Under the frame of Project APPLAUSE, we tested the possibility to use four alien/invasive wood species for particleboard production. For that purpose, black locust (Robinia pseudoacacia), honey locust (Gleditsia triacanthos), staghorn sumac (Rhus typhina) and tree of heaven (Ailanthus altissima) were used. Preparation of particles and particleboards was done in laboratory conditions. The properties of particleboards were influenced by the selection of wood species. Differences already appeared with the morphological characteristics of the particles. Best properties, in general, were obtained using staghorn sumac (highest bending strength and modulus of elasticity, relatively high internal bond and relatively low thickness swelling). Relatively good properties were also determined at particleboards made from tree of heaven (relatively high bending strength and modulus of elasticity, highest internal bond) and honey locust (low thickness swelling relatively high bending strength and modulus of elasticity), although some improvements needs to be made, with regard to the board composition and manufacturing process. [ABSTRACT FROM AUTHOR]
- Published
- 2019
31. Formaldehyde barrier efficiency of melamine impregnated paper and melamine edge-banding tape surfaced particleboard and MDF
- Author
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Medved, Sergej, primary and Forštnarič, Jernej, additional
- Published
- 2018
- Full Text
- View/download PDF
32. Vpliv klimatskih pogojev na poves nekaterih lesnih ploščnih kompozitov
- Author
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Medved, Sergej, Jambreković, Vladimir, Kraigher, Hojka, and Humar, Miha
- Subjects
lesni ploščni kompoziti ,poves ,obremenitev ,upogib - Abstract
Uporabnost lesnih ploščnih kompozitov, še posebej tistih namenjenih uporabi v gradbeništvu je pogojena z njihovim obnašanjem v okolju s spreminjajočimi klimatskimi pogoji in pri dalj časa trajajočih obremenitvah. Za ugotavljanje vpliva klimatskih pogojev na poves lesnih ploščnih kompozitov smo uporabili pet različnih lesnih ploščnih kompozitov namenjenih tako uporabi v gradbeništvu, kakor tudi splošni oz. pohištveni rabi. Iz vsake vrste plošče smo izžagali šest preskušance velikosti 180 mm × 30 mm × debelina, ki smo jih izpostavili trem različnim klimatskim pogojem. Za ugotavljanje povesa smo uporabili štiritočkovni upogibni test. Poves preskušancev pri štiritočkovnem upogibnem testu je odvisen tako od vrste lesnega ploščnega kompozita kakor tudi od klimatskih pogojev. Ugotovimo lahko, da imajo plošče, ki so namnjene uporabi v gradbeništvo (FP–Bu, OSB, KIP P5) manjši poves kakor pri iverni plošči namenjeni splošni oz. pohištveni uporabi (IP P2). Majhen povesa pri nizki in normalni klimi smo ugotovili tudi pri MDF plošči. Pri ploščah narejenih iz manjših gradnikov (KIP P5, IP P2 in MDF) smo ugotovili, da je pri preskušancih izpostavljenih višji vlažnosti prišlo do predčasne porušitve in sicer je pri KIP P5 prišlo do porušitve po 30 minutah, pri IP P2 in MDF pa celo po 1 minuti obremenitve.
- Published
- 2016
33. Forest and wood: idea, invention, innovation (in forestry, wood technology and paper industry): book of abstracts of the Scientific Meeting Forest and Wood, Ljubljana, May 12th, 2016
- Author
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Kraigher, Hojka, Humar, Miha, Emri, Igor, Nasilowska, Sylwia A., Kacprzak, Mariusz, Kotlarz, Jan, Rynkiewicz, Alicja, Bajc, Marko, Brezovar, Jernej, Finžgar, Domen, Kladnik, Andraž, Capuder, Rok, Levanič, Jaka, Poljanšek, Ida, Oven, Primož, Sežun, M., Mešl, M., Zule, J., Lavric, G., Gregori, A., Mazur, Anna, Mrak, Tanja, Gričar, Jožica, Železnik, Peter, Zavadlav, Saša, Voglar, Grega E., Hafner, Polona, Ferlan, Mitja, Levanič, Tom, Pogorelčnik, Ajda, Lesar, Boštjan, Thaler, Nejc, Lesar, Matej, Kržišnik, Davor, Ugovšek, Aleš, Šubic, Barbara, Rep, Gregor, Žigon, Jure, Šernek, Milan, Hora, Guido, Medved , Sergej, and Jambreković, Vladimir
- Subjects
WOOD SCIENCE AND TECHNOLOGY ,FORESTRY - Published
- 2016
34. Vpliv zrnatosti brusnega papirja na emisijo formaldehida iz ivernih plošč
- Author
-
Medved, Sergej, primary and Krajšek, Gregor, additional
- Published
- 2017
- Full Text
- View/download PDF
35. Influence of Liquefied Wood pH Values As a Hardener on Particleboards Properties
- Author
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Antonović, Alan, Jambreković, Vladimir, Ištvanić, Josip, Španić, Nikola, Medved, Sergej, and Trposki, Zoran
- Subjects
Liquefied wood ,Particleboards ,Hardeners ,Urea- and Melamine-Urea Formaldehyde Resins ,technology, industry, and agriculture - Abstract
Wood liquefaction is a new technique of chemical wood processing, and its aim is to convert wood material in environment frendly and biodegradable polymer materials, and increase percentage of its utilization. Nowdays, according to previous published researches, maximum attention attracted wood liquefaction in presence of some organic reagents and the most interesting are two methods. The first method is the preparation in presence of phenol, which resulted in liquefaction products rich with phenol units. The second liquefaction method was achieved in presence of polyhydric alcohols. Wood composite materials and fragmented wood-based panels (particleboards, fibreboards, OSB, MDF, WPC and other panels) are materials of the future. With their wide spectra of potential applications these materials occupy almost all fields of use. Quality of wood composite materials does not exclusively depend on wood species and their properties applied in production, but with application of other essential non-wooden synthetic chemical components, such as a different types of resins and adhesives, hardeners and paraffin emulsion, which were designed in accordance with the requirements of everyday use and utilisation demands. According to above, this research has focused on the possibility of using liquefied wood (LW) as a hardener in particleboards production, and the impact of different LW pH values on the polymer structure and adhesion-cohesion properties of polymerization of urea-formaldehyde (UF) and melamine-urea- formaldehyde (MUF) adhesives. Furthermore, aim of this research was also the influence of mentioned new adhesion system on the particleboards physical and mechanical properties, and formaldehyde emission.
- Published
- 2015
36. Acetylated wood cellulose as polymer base of bio composite materials
- Author
-
Španić, Nikola, Jambreković, Vladimir, Medved, Sergej, Antonović, Alan, and Šubarić, Drago
- Subjects
wood ,cellulose ,acetylation ,bio composite materials ,FT-IR ,TGA - Abstract
Natural polymeric materials are interesting alternative to petrochemical products with potential application in almost all areas of human activities. However, despite the fact that the use of natural polymers based on polysaccharides, proteins and agricultural raw materials are very common, studies on potential use of acetylated cellulose isolated from wood as bio composite materials polymer matrix are very scarce. Specifically, acetylated cellulose application is almost exclusive to preparation of membranes for desalination, medical dialysis and filtration, while the commercial application of cellulose esters in terms of structural materials is at very low level, which regularly involves the synthesis and application of mixed cellulose esters (eg, cellulose acetate butyrate as material for tool handles and/or glasses frames). Wishing to expand the field of cellulose acetate application to bio composite wood material systems, the possibilities of cellulose isolation and its acetylation from two domestic commercially meagrely used wood species was investigated in this paper. Quantitative analysis of laboratory acetylation process beside chemical analysis of gained product by infrared spectroscopy (FT-IR) indicates the impact of water present in cellulose structure on values of mass increase, number of acetyl groups and the degree of acetylation. Results of thermogravimetric analysis (TGA) confirmed thus obtained results.
- Published
- 2014
37. Influence of pH Value of Liquefied Wood as a Hardener of Urea-Formaldehyde Resin with 4 % Melamine Addition in Particleboard Production
- Author
-
Antonović, Alan, Jambreković, Vladimir, Španić, Nikola, Medved, Sergej, Ištvanić, Josip, Devčić, Matej, and Grbac, Ivica
- Subjects
technology, industry, and agriculture ,Liquefied wood ,particleboards ,urea-formaldehyde resin ,melamine-urea-formaldehyde resin ,hardeners ,pH value - Abstract
Wood liquefaction is novel method, and its aim is to convert wood material in biodegradable polymer materials and increase percentage of wood utilization. The most interesting are two wood liquefaction methods. The first one is the preparation in presence of phenol, which resulted in liquefaction products rich with phenol units. The second liquefaction method was achieved in presence of alcohols, especially polyhydric alcohols, and the gained products can be used as polyols. Panels based on fragmented wood and wood composite materials, respectively, are materials of the future. With their wide spectra of potential applications these materials occupy almost all fields of use. The quality of wood composite materials does not exclusively depend on wood species and their properties applied in production, and with the application of other necessary synthetic chemical components like different resins, hardeners and parafine emulsions, is designed according to utilization demands. With regard to this issue, this paper is focused and the main aim was to analyse the possibility of using liquefied wood (LW) as a hardener and the impact of its various pH values in the adhesion process of urea-formaldehyde (UF) and melamine-urea-formaldehyde (MUF) resin with the addition of 4% melamine at high temperatures, and the impact of its actions on the particleboards physical-mechanical properties and formaldehyde emission.
- Published
- 2014
38. Influence of treatment and facade implementation on the blue staining on facade of the model object
- Author
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Žlahtič, Mojca, Thaler, Nejc, Medved , Sergej, Pohleven, Franc, Krže , Luka, Željko, Marko, Lesar, Boštjan, and Humar, Miha
- Subjects
WOOD SCIENCE AND TECHNOLOGY - Published
- 2014
39. Novel types of wood composite materials modified with liquefied wood
- Author
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Antonović, Alan, Jambreković, Vladimir, Ištvanić, Josip, Devčić, Matej, Medved, Sergej, and Iliev, Borče
- Subjects
technology, industry, and agriculture ,liquefied wood ,wood composite materials ,resin modification ,complex mixtures - Abstract
Wood is one of the most abundant and accessible renewable resources available to men. With growing emphasis on sustainable development, new methods involving alternative wood use are being explored. An approach that has been intensively researched in recent years is wood liquefaction, with the aim of converting wood material in a biodegradable polymer materials and increase the percentage of wood utilization. In previous years, the researchers were liquefied chemical wood components such as cellulose, hemicellulose and lignin in liquid bioactive materials. Wood liquefaction is based on the fact that the wood components are chemically derivatised, thus increasing their solubility in certain solvents which dissolved macromolecules can subsequently used for the preparation of useful polymer materials, or macromolecules are partially decomposed into smaller soluble oligomers which are then used as a source of raw materials for further use. Particularly interesting is the use of liquefied wood as a source of raw materials from which can be produced various wood composite materials (particleboard, fibreboard panels, MDF, WPC), and therefore replace some synthetic polymers based on the conventional source - oil. Therefore, the aim of this paper is to give an overview of using liquefied wood in synthetic resins modification as a raw materials for the novel types of composite materials production.
- Published
- 2013
40. Strength comparison of joints at window frames
- Author
-
Hrovatin, Jasna, Prekrat, Silvana, Berginc, Jordan, Šernek, Milan, Zupančić, Anton, Oblak, Leon, and Medved Sergej
- Subjects
wood ,window ,joint ,strength ,mechanical properties - Abstract
The strength of joints with a wooden ring, which are protected by international patent was compared with the strength of tenon dowel joints, and consequently the applicability and suitability for producing such window frames was established. The strength of different implementations of angular joints of window profiles was tested on a tensile-testing machine. It was established that the average ultimate strength of joints with a wooden ring was higher than the ultimate strength of tenon joints, which was chosen as an upper reference limit.
- Published
- 2013
41. Thermal characteristics some wood-based panels used in contruction
- Author
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Medved, Sergej, Jambreković, Vladimir, Iliev, Borče, Gorišek, Željko, and Iliev, Borče
- Subjects
wood-based panels ,thermal conductivity ,thermal diffusivitiy ,density - Abstract
Wood–based panels are widely used panels not only for furniture but also for construction purposes, especially for prefabricated houses. They can be used for flooring, roofing, walls and as insulation. Although wood–based panels used as load bearing construction materials have to have good mechanical properties it can be determined that they even have relatively good thermal characteristics (low thermal conductivity). Despite the fact that thermal characteristics of panels are related to the density of panel it is also evident that there is a difference among different panels related to size and type of constituent. The aim of paper is to present thermal characteristics of some wood – based panels used in construction. It was determined that thermal characteristics (thermal diffusivity) depend on the type of constituent, type of panel and its density.
- Published
- 2013
42. CHEMICAL COMPOSITION OF FIRED ALEPPO PINE (Pinus halepensis Mill.) BIOMASS.
- Author
-
Antonović, Alan, Barčić, Damir, Španić, Nikola, Medved, Sergej, Stanešić, Juraj, Podvorec, Tomislav, Lozančić, Matija, Štriga, Sebastijan, and Ištvanić, Josip
- Subjects
ALEPPO pine ,LIGNOCELLULOSE ,BIOMASS ,CELLULOSE ,FOREST fires - Abstract
The Republic of Croatia, as well as the rest of the Mediterranean European countries, is increasingly faced with the problem of forest fires and their immediate aftermath. After the forest fires, significant quantities of fired trees as lignocellulosic biomass are left behind, and the question arises as to what degree they are chemically degraded or whether they still possess all the properties for further application in mechanical or chemical processing. Therefore, the aim of this study was to research the impact of forest low ground fire and high fire of the treetops on the Aleppo pine (Pinus halepensis Mill.) chemical composition as a biomass quality property. The study was carried out by determining the group chemical composition of fired and non-fired wood anatomical parts for comparison with the fired ones, by sampling the rings at the height of the trees 0 m, 2 m 4 m. The results obtained show that the non-fired bark contains a appreciably higher content of ash, accessory materials (extractives) and lignin, and a considerably lower content of polysaccharides cellulose and polyoses (hemicellulose) than sapwood and heartwood, which is similar in comparison to the results of previous studies. The bark results show a notable difference in reduced ash, cellulose and lignin content, and in increased accessory materials and wood polyoses (hemicellulose) content between the non-fired and fired wood. Furthermore, the content of individual chemical components of fired bark at different forest fires heights of 0, 2 and 4m for each sample did not differ substantially. Contrary to fired bark, sapwood and heartwood does not have considerable differences in the chemical composition of non-fired and fired wood, as well as on different forest fires heights. The results obtained show that forest fires do not have any effect on overall Aleppo pine sapwood and heartwood; it is fired wood bark that takes on all the damage caused by the high temperature during a forest fire. In addition, the fired sapwood and heartwood still possess all the chemical properties for further application. [ABSTRACT FROM AUTHOR]
- Published
- 2018
43. Quality of Wood Based Panel Surface and Its Impact on Surfacing with Melamine Impregnated Paper
- Author
-
Medved, Sergej, Jambreković, Vladimir, Điporović-Momčilović, Milanka, Wieland, S, and Schnabel, T
- Subjects
particleboard ,fiberboard ,melamine impregnated paper ,surface modification ,FTIR - Abstract
Delamination of paper could also occur if the surface of the board is contaminated – unreactive. Such low reactivity of board could be due to the high density (as we mentioned before) usage of water repelling substance like wax emulsion or even due to the thermal modification, which partially already occurs during pressing. Quality surface of board is important because the melamine- impregnated papers used nowadays are impregnated with high reactivity resins. At the end of impregnation resin the resin is cured to a predetermined degree and when impregnated paper is paced together with the board into the press the resin has to be reactivated so that it can wet and penetrate into board surface and fully cure in a relatively short time (less than 30 seconds). The aim of this paper is to present the impact of board quality, especially surface quality on the surfacing with impregnated paper. For this purposes commercially available unsanded and sanded particleboard and MDF boards furniture grade were used. For surfacing white melamine impregnated paper marked 80/200 was used. Sanded boards were thermally modified at temperatures 190, 210 and 230°C in oven. Unsanded and sanded boards were sprayed with wax emulsion. Prior to surfacing boards were conditioned at 20°C and 65% relative air humidity. After 5 days of climatization boards were surfaced at 190°C, 2.5 N/mm2. At unsurface board density distribution, surface pH value, wetting contact angle was determined. Surface of board was also analyzed by FT–IR spectrometer. At surface boards only bond strength by surface soundness test was determined.
- Published
- 2012
44. Wood-based panels and environment
- Author
-
Medved, Sergej, Antonović, Alan, Španić, Nikola, Jambreković, Vladimir, and Grbac, Ivica
- Subjects
wood based panels ,environment - Abstract
Increasing growth of wood-based panel sector which we faced at the beginning of this decade and increasing goal to lover the emission of greenhouse gasses placed wood and woodbased panels into new perspective. To lower the emission of greenhouse gasses such a materials should be use that causes as little as possible impact on our environment. Looking at the production process it is known that raw material and energy is needed. In this paper we are going to present how the wood-based panel production process influences the environment, and why, despite the intensive process this production has lower impact on environment compared to other non-wood furniture and construction materials.
- Published
- 2011
45. Properties of particleboards made by using an adhesive with added liquefied wood: Lastnosti ivernih plošč, izdelanih z uporabo lepila z dodanim utekočinjenim lesom
- Author
-
Čuk, Nataša, Kunaver, Matjaž, and Medved, Sergej
- Abstract
In this study, three-layer particleboards were produced using liquefied wood in an adhesive mixture. The influence of two different formaldehyde resins: melamine-formaldehyde and melamine-urea-formaldehyde resin and two various catalysts: ammonium sulfate and ammonium formate on the particleboard properties was investigated. There were also two pressing parameters examined: temperature and time. The following physical and mechanical properties of particleboards were measured: board thickness, density, moisture content, bending strength and modulus of elasticity, internal bonding strength, surface soundness, thickness swelling and formaldehyde content. The results showed that properties of produced particle boards were better when melamine-formaldehyde resin and ammonium formate as a catalyst were used in combination with liquefied wood in the adhesive mixture. Also, mechanical properties were improved as the press time and press temperature increased. The optimal mechanical properties of particleboards made with the utilization of the liquefied wood in the adhesive mixture were achieved at 3 min press time and 180 °C press temperature using melamine-formaldehyde resin and 3 % of ammonium formate as a catalyst. A very important characteristic is the low formaldehyde content and that is extremely important in the provision of better quality of life. With the liquefaction of wood and the application of liquefied wood in the particleboard production wood biomass exploitation could be significantly increased. We are able to produce new materials from renewable resources that can be a great alternative to the raw materials, originating from crude oil. Izdelali smo trislojne iverne plošče, kjer smo za pripravo lepila uporabili utekočinjen les. Ugotavljali smo, kako v kombinaciji z utekočinjenim lesom na lastnosti ivernih plošč vplivata dve različni formaldehidni smoli: melamin-formaldehidna in melamin-urea-formaldehidna smola, ter dva različna katalizatorja: amonijev sulfat in amonijev formiat. Ugotavljali smo tudi vpliv dveh parametrov stiskanja, in sicer temperature stiskanja in časa stiskanja. Fizikalne in mehanske lastnosti, ki smo jih ivernim ploščam določili, so bile: debelina plošče, gostota, vsebnost vlage, upogibna trdnost in modul elastičnosti, razslojna trdnost, čvrstost površine, debelinski nabrek in vsebnost prostega formaldehida. Rezultati so pokazali, da smo izboljšali lastnosti ivernih plošč, ko smo v kombinaciji z utekočinjenim lesom uporabili melamin-formaldehidno smolo in amonijev formiat kot katalizator. Ugotovili smo tudi, da so se lastnosti izdelanih ivernih plošč s časom in temperaturo stiskanja izboljšale. Optimalne lastnosti ivernih plošč, pri katerih smo lepilni mešanici dodali utekočinjen les, smo dosegli pri času stiskanja 3 min in temperaturi stiskanja 180 °C, pri uporabi melamin-formaldehidne smole in 3 % amonijevega formiata kot katalizatorja. Zelo pomembna pri izdelanih ivernih ploščah je tudi majhna vsebnost prostega formaldehida, kar močno vpliva na izboljšanje kvalitete bivanja. Z utekočinjanjem lesa in njegovo uporabo pri izdelavi ivernih plošč povečamo izrabo lesne biomase. Iz obnovljivih virov tako lahko sintetiziramo nove materiale, ki so odlična alternativa materialom, ki jih sicer pridobivamo iz surove nafte.
- Published
- 2011
46. Properties of liquefied wood modified melamine-formaldehyde (MF) resin adhesive and its application for bonding particleboards
- Author
-
Čuk, Nataša, primary, Kunaver, Matjaž, additional, Poljanšek, Ida, additional, Ugovšek, Aleš, additional, Šernek, Milan, additional, and Medved, Sergej, additional
- Published
- 2015
- Full Text
- View/download PDF
47. Wood-based panels as material for sustainable use of natural resources
- Author
-
Medved, Sergej, Antonović, Alan, Jambreković, Vladimir, Čuk, Nataša, Kunaver, Matjaž, and Despot, Radovan
- Subjects
wood-based panels ,insulation properties ,formaldehyde emission ,liquefied wood - Abstract
Wood is important natural renewable raw material that can be used for many purposes. One can say that wood and wood based products follows us from the cradle to grave. From the mid of previous century we started to massively produced and used an interesting material called wood-based panels. Wood based panels as widely used material is mostly out of wood, especially from wood residues so one can say that this industry contributes to the sustainable use of natural resources. It can be also expressed that wood-based panels are a way of recycling of wood residues. Since they are made mostly out of wood, they also store CO2. And this is not their only advantage. Second very important advantage is also its good mechanical and physical properties, which can also be altered according to their purpose of usage. Like wood, they also have good isolation properties (especially low density fibrous materials), hence contributing to lower energy consumption when used as a building material (wooden houses, prefabricated houses, passive houses, etc). One of the disadvantages of those materials is the emission of formaldehyde due to the usage of synthetic formaldehyde based adhesives. But since wood can be liquefied and later used as partial substitute for synthetic adhesives. With the usage of liquefied wood the formaldehyde emission was lowered, and since more natural material was used for the production of wood based panels they became friendlier. The aim of this paper is to show the possibilities that wood based products offer to us as a material for various purposes and as a material that can help us to reduces the use of crude oil as raw material.
- Published
- 2010
48. Dimensional stability of particleboards
- Author
-
Medved, Sergej, Điporović-Momčilović, Milanka, Popović, Mlađan, Antonović, Alan, Jambreković, Vladimir, Ristić, Ratko, Medarević, Milan, and Popović, Zdravko
- Subjects
fungi ,particleboard ,thickness swelling ,wood species ,resin content ,density - Abstract
When exposed to water or moist environment particleboards tend to swell and expand in all directions. The most visible is swelling in thickness that is higher than horizontal expansion. Thickness swelling of particleboards is influenced by many factors. Among the most important are raw material used, type and share of adhesive used and density of the produced boards. The purpose of this paper is to present the impact of wood species used, share of adhesive and board density on thickness swelling after 24-hour immersion in water. Several three-layer and single-layer particleboards bonded with urea-formaldehyde adhesive were made in laboratory conditions where wood species (three-layer made from spruce, beech, oak and poplar particles), resin content (three-layer, core layer: 6 to 9% ; surface layer: 10 to 13%) and density of board (single-layer with density between 0.7 and 1.0 g/cm3) were altered. In boards where resin content and density was altered industry made particles were used. Thickness swelling was determined with 24-hour immersion test. It was determined that the highest swelling was determined when beech particles were used, and the lowest when oak and spruce particles were used. The biggest changes in swelling and pressure were observed when the resin content was changed in the core layer. The swelling was also influenced by the density of boards. It was determined that the highest swelling was observed in boards with the highest density.
- Published
- 2010
49. Influence of some pressing parameters on properties of particleboards modified with liquefied wood
- Author
-
Antonović, Alan, Jambreković, Vladimir, Španić, Nikola, Tišler, Vesna, and Medved, Sergej
- Subjects
technology, industry, and agriculture ,liquefied wood (LW) ,composite materials ,urea-formaldehyde (UF) resin modification ,liquefied wood-formaldehyde (LWF) resin - Abstract
Wood composites are materials of future, and with their wide spectra of potential applications occupy almost all fields of usage. In group of wood composite materials from fragmented wood, "valueless" biomass and residues after usage are converted to valuable material. The problem with application of other necessary synthetic chemical components (particularly adhesives), mainly oil derivatives, which according to oil shortage and price growth on world market can endanger that production, has been the subject of many scientific researches which gave positive results. The above mentioned adhesives are essential non-wooden components in wood composite production. Linked to above, many researches are focused on wood liquefaction and liquefied wood (LW) application as potential adhesives, apropos to gluing solid particles with liquid wood. Based on previous studies, maximum attention was given to LW applications in modification of phenol-formaldehyde (PF) resins, polyurethanes, saturated and unsaturated polyesters, isocyanates and epoxy resins, and their further application in novel material types. It is evident that because of their "inferior" properties, researches on urea-formaldehyde (UF) resins failed, as well as researches on preparations of adhesives on UF base modified with LW. Therefore, the subject of this study was researching the influence of specific pressing parameters on liquefied wood compatibility with UF resins, its influence on polymer structure and adhesion-cohesion properties of modified UF adhesives, and particleboards physical-mechanical properties and formaldehyde emission.
- Published
- 2009
50. Utjecaj promjene vlažnosti zraka na čvrstoću bukovih ploča od cjelovitog drva
- Author
-
Pervan, Stjepan, Prekrat, Silvana, Gorišek, Željko, Medved, Sergej, Straže, Aleš, and Grbac, Ivica
- Subjects
čvrstoća na smik ,bukva ,vlaga zraka - Abstract
U radu je analizirana smicajna čvrstoća sljepljenih spojeva bukovine, kao i čimbenici koji utječu na nju, poput debljine drva, vlage zraka i načina termičke obrade drva. Na osnovu dosadašnjih znanstvenih spoznaja analizirana su i svojstva bukovine koja su ključna za čvrstoću ljepljenog spoja. Prikazana je statistička usporedba eksperimentalnih rezultata čvrstoće na smik paralelno s vlakancima dužinsko-širinski ljepljenih ploča izrađenih od parene i neparene bukovine. Uzorci su izrađeni u dvije različite debljine, 20 (neparena bukovina) i 40 mm (parena i neparena bukovina), te zatim izlagani trima diferencijalnim klimama od 33%, 65% i 88% relativne vlage zraka pri sobnoj temperaturi. Uspoređeni su rezultati s obzirom na debljine uzoraka, različite vlažnosti zraka i načine termičke obrade drva. Napravljena je statistička analiza studentovim t-testom uz razinu značajnosti 0, 05 te je utvrđeno da ne postoji statistički značajna razlika pri usporedbi čvrstoće na smik kod grupa 4, 7, 8, 9, 10 i 13, koje ukazuju da debljina uzorka i postupak termičke obrade bukovine nemaju utjecaj na čvrstoću sljepljenog bukovog spoja. Utvrđeno je da nije zadovoljen uvjet homogenosti varijance u grupama 1, 11, 12, te je stoga korišten Mann-Whitneyev U test koji je pokazao statistički značajnu razliku u čvrstoći neparenih uzoraka debljine 20 mm pri izlaganju vlažnostima zraka od 33 i 65 % (promjena vlage zraka iz izuzetno suhih prema umjerenim uvjetima ima utjecaja na tanje uzorke), te je također za uzorke debljine 40 mm dokazano da promjena vlage s suhih i umjerenih uvjeta na izuzetno vlažne ima značajnog utjecaja na čvrstoću bukovog sljepljenog uzorka. Također je utvrđena statistički značajna razlika u čvrstoći na smik između grupa uzoraka parene bukovine izlaganih vlagama zraka od 33, 65, 88%, gdje vrijednost čvrstoće izuzetno pada pri povećanju relativne vlage zraka. Potvrđeno je da termički tretman obrade drva (parenje) ima utjecaja na čvrstoću spoja koja je manja kod parenog u odnosu na nepareno drvo.
- Published
- 2009
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