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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.

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.

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.

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 %.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.