Hrapavost površine rezanog furnira u smislu nedostataka i varijabilnosti strukture drva – utjecaj blage hidrotermičke obrade

Τhis study deals with the surface roughness and quality of oak sliced veneers and how these characteristics are influenced by the presence of knots, and other defects associated to knots. The variability of roughness is thoroughly examined along the oak stem, exploring also how it differentiates going from one veneer to the adjacent one, cut in different wood depths of the same sawn wood piece in defect and non-defect areas. The expected vertical variability of morphological characteristics did not influence significantly the surface roughness along the stem, which favors the sliced veneers application and performance. The veneers obtained from the edges of the veneer package presented surfaces of high roughness. The smoothest surfaces were recorded in some of the areas on or peripherally of the living intergrown knots. Apart from the cases of large or dead knots that break and result in detrimental cavities, the small live knots do not influence negatively the roughness and therefore, neither the veneer processing demands, nor the overall quality of the final veneer-based product. In order to improve the surface quality of oak sliced veneers and to investigate the response of both defect- and non-defect areas to the hydrothermal modification, two mild and short-term hydrothermal treatments were applied. Among these treatments, only the mildest one (110 ºC) managed to improve significantly the surface quality, concerning both the defect and non-defect areas, while the treatment at 130 ºC did not reveal a significant change of the surface roughness of veneers.U radu je istraživana hrapavost površine i kvaliteta rezanoga hrastova furnira te utjecaj kvrga i drugih nedostataka povezanih s kvrgama na hrapavost površine i kvalitetu tog furnira. Varijabilnost hrapavosti temeljito je ispitana duž hrastova debla te među susjednim furnirima rezanim na različitim dubinama istog debla u područjima s greškama i bez njih. Očekivana vertikalna varijabilnost morfoloških obilježja drva duž debla nije značajno utjecala na hrapavost površine furnira, što pogoduje primjeni i svojstvima rezanog furnira. Površina furnira uzetih s rubova paketa bila je vrlo hrapava. Površine s najmanjom hrapavošću bile su one s područja zdravih uraslih kvrga ili periferno od njih. Osim velikih ili mrtvih kvrga, koje pucaju i rezultiraju štetnim šupljinama, male zdrave kvrge ne povećavaju hrapavost površine furnira, a time ne utječu na zahtjeve obrade furnira ni na kvalitetu proizvoda od njih. Kako bi se poboljšala kvaliteta površine hrastovih rezanih furnira i istražio utjecaj područja s greškama i bez njih na hidrotermičku modifikaciju, primijenjena su dva blaga i kratkotrajna hidrotermička tretmana. Od tih tretmana samo je blaži (110 ºC) uspio znatnije poboljšati kvalitetu površine, kako područja s greškama, tako i područja bez grešaka, dok tretman pri 130 ºC nije bitno utjecao na promjenu hrapavosti površine furnira

Bondability of black locust (Robinia pseudoacacia) and beech wood (Fagus sylvatica) with polyvinyl acetate and polyurethane adhesives

In the previous years, black locust wood (Robinia pseudoacacia) has been participating in the European subsidizing programme of tree species cultivation, aiming in the establishing of new plantations in many European countries, therefore large quantities of this species is going to be harvested in the forthcoming years and the examination of its properties would be very crucial for future utilization. In the present research, the bondability of black locust wood is examined using two different adhesives, Polyvinyl acetate and Polyurethane and two different pressure levels. Beech wood is also included in the research for comparative reasons. According to the results, the shear bond strength of black locust wood was found to be satisfying, especially in the presence of Polyvinyl acetate adhesive and the less intensive pressure used during the specimens’ construction, although it was found lower compared to beech wood, referring both to Polyvinyl acetate and Polyurethane adhesive

Utjecaj toplinske modifikacije na kvalitetu drva pajasena

Ailanthus altissima (Miller) Swingle is a deciduous, fast-growing species that can tolerate extreme climatic conditions and is particularly invasive. In the framework of climate change, and the imperative need for carbon greenhouse gases sequestration, this species could acquire increasing importance through its utilization in the construction of wood based products and structures, due to its satisfying properties combined with its fast growth. This study determines for the first time the influence of thermal treatment, under different conditions (190 ºC, 210 ºC, 230 ºC for 2 hours), on some crucial physical, hygroscopic and mechanical properties of wood, in an attempt to improve its intense hygroscopic nature and not so desirable colour. Thermal treatment affected the dimensional stability and water absorbing capacity of wood in a positive way, decreasing EMC, swelling (tangential–radial) and adsorption percent, compared to untreated wood. The anisotropy of wood was decreased only to a small extent. The total surface colour differences (ΔΕ*), prior and after treatment, ranged between 0.48 and 54.57, and appeared to be well correlated with treatment temperature. Only the most intensive treatment influenced negatively the modulus of rupture and impact bending strength of wood, while the elasticity and compression strength of treated wood were proved to be similar to those of untreated wood. Tree-of-heaven could benefit from a mild or medium intensity heat treatment process, in order to be modified to an aesthetically pleasing wood with enhanced hygroscopic nature and properties, facilitating its use in cabinetry and in variable indoor and outdoor non-structural applications.Ailanthus altissima (Miller) Swingle listopadna je, brzorastuća i invazivna vrsta drva koja je otporna na ekstremne klimatske uvjete. S gledišta klimatskih promjena i nužne potrebe za sekvestracijom stakleničkih plinova, ta bi vrsta drva zbog svojih svojstava, u kombinaciji s brzim rastom, mogla steći sve veće značenje u graditeljstvu. Ovim se istraživanjem prvi put utvrđuje utjecaj toplinske modifikacije pri različitim temperaturama na ključna fizička i mehanička svojstva drva radi smanjenja njegove higroskopnosti i dobivanja poželjnije boje. Toplinska modifikacija pozitivno je utjecala na dimenzijsku stabilnost te na smanjenje upijanja vode, ravnotežnog sadržaja vode, bubrenja (tangentno – radijalno) i adsorpcije u usporedbi s nemodificiranim drvom. Anizotropnost drva samo se neznatno smanjila. Ukupna promjena boje (ΔE*) površine drva prije i nakon toplinske modifikacije bila je u rasponu od 0,48 do 54,57 i pokazala je dobru korelaciju s temperaturom modifikacije. Samo je modifikacija s najvišom temperaturom negativno utjecala na modul loma i čvrstoću na udar, dok su elastičnost i čvrstoća na vlak toplinski modificiranog drva bili podjednaki kao i nemodificiranog drva. Slab ili umjeren postupak toplinske modifikacije može modificirati drvo pajasena u estetski ugodno drvo poboljšanih svojstava i smanjene higroskopnosti te time olakšati i proširiti njegovu uporabu u proizvodnji namještaja i nenosivih elemenata u graditeljstvu

Utjecaj toplinske obrade na promjenu boje i dimenzijsku stabilnost bukovine (Fagus sylvatica L.)

Thermal modifi cation of wood permanently alters several of its chemical and physical properties. Beech wood is one of the most important hardwoods in Central and Eastern Europe and is extensively used in furniture production. In this study the effects of thermal modification of beech wood (Fagus sylvatica L.) on hygroscopic properties were examined and the color changes of the treated wood were determined. Beech wood has been subjected to a heat treatment at the temperature of 180 °C for five different durations ranging from 2 to 10 h. A more intense, gradual color change of the treated samples was observed after 4-h treatment, whereas in some other cases the recorded alterations were less intense. The most pronounced color differentiations compared to untreated samples occurred in 8-h and 10-h treatments. Dimensional stability and absorption were measured after 1-h, 3-h, 6-h, 1 day and 3 days immersion in water. The 8-h treatment duration exhibits the greatest reduction of swelling and absorption percentage.Toplinska modifikacija drva trajno mijenja neka njegova kemijska i fizikalna svojstva. Bukovina je jedna od najvažnijih vrsta tvrdog drva u srednjoj i istočnoj Europi, a uvelike se upotrebljava za proizvodnju namještaja. U ovoj su studiji predstavljeni rezultati istraživanja utjecaja toplinske modifikacije bukovine (Fagus sylvatica L.) na neka higroskopna svojstva i promjene boje toplinski obrađenog drva. Bukovina je podvrgnuta toplinskoj obradi pri temperaturi 180 °C i tijekom pet različitih trajanja procesa obrade, od dva do deset sati. Intenzivnije promjene boje toplini izlaganih uzoraka uočene su nakon četiri sata, dok su u drugim slučajevima zabilježene manje intenzivne promjene. Najintenzivnije razlike u boji u usporedbi s netretiranim uzorcima dogodile su se nakon osam i deset sati obrade. Dimenzijska stabilnost i apsorpcija mjerene su nakon jedan sat, tri sata, šest sati, jedan dan i tri dana potapanja uzoraka u vodi. Nakon potapanja uzoraka u vodi u trajanju od osam sati zabilježeno je najveće smanjenje bubrenja i postotka apsorpcije

Changes in Hygroscopic Properties of Poplar and Black Pine Induced by Thermal Treatment

The aim of the present research is to comprehend the response of poplar (Populus sp.) and pine (Pinus nigra L.) wood to thermal modification at the temperature of 180°C and 200°C, for 3 different treatment durations of 3, 5 and 7 hours, in the presence of air, by examining their physical and hygroscopic properties and comparing these species properties one another. Specifically, in this research, the mass loss of the samples due to the treatment, the density, the equilibrium moisture content (EMC) and the hygroscopic properties (radial, tangential and longitudinal swelling and absorption percentages) were examined. As the treatment intensity increased, the mass loss of pine and poplar boards due to treatment also increased, which corresponds to the loss of moisture, and the chemical constituents of wood due to their degradation (evaporation of volatile extracts, loss of products through thermal degradation etc.). The thermal treatment has led to a reduction in the recovery rate of the pine and poplar plates of their original weight due to reduced moisture recovery, which is more pronounced as the treatment temperature and duration increase. The EMC of all heat-treated pine and poplar samples was reduced compared to the corresponding control value, even in the case of the less intensive treatment (180°C-3h) and as the intensity increased, EMC decreased further (20.73%-38.43% for pine and 18.76%-49.20% for poplar). Thermal treatments reduced the density of pine (0.76-20.24%) and poplar (1.04-24.42%), and as the treatment intensity increased, larger reduction was recorded. The hygroscopic properties of heat-treated pine were improved in every case due to thermal treatments. The most intensive treatment tended to slightly increase the adsorption and radial-tangential swelling rates, without approaching the control levels. Referring to poplar, all treatments, even the less intensive ones, improved the hygroscopic nature of wood, reducing the adsorption and tangential-radial swelling rates compared to the control sample. Therefore, confirming the results of literature, the thermal treatment was found to improve the hygroscopic behavior of pine and poplar and to further reduce tangential swelling levels in relation to radial direction, contributing to the limitation of wood anisotropy

Bondability of black locust ("Robinia pseudoacacia") and beech wood ("Fagus sylvatica") with polyvinyl acetate and polyurethane adhesives

In the previous years, black locust wood (Robinia pseudoacacia) has been participating in the European subsidizing programme of tree species cultivation, aiming in the establishing of new plantations in many European countries, therefore large quantities of this species is going to be harvested in the forthcoming years and the examination of its properties would be very crucial for future utilization. In the present research, the bondability of black locust wood is examined using two different adhesives, Polyvinyl acetate and Polyurethane and two different pressure levels. Beech wood is also included in the research for comparative reasons. According to the results, the shear bond strength of black locust wood was found to be satisfying, especially in the presence of Polyvinyl acetate adhesive and the less intensive pressure used during the specimens’ construction, although it was found lower compared to beech wood, referring both to Polyvinyl acetate and Polyurethane adhesive

UTILIZATION OF WOOD OF EVERGREEN HARDWOODS IN THE PRODUCTION OF COMPOSITE BOARDS

THE HARVESTED MATERIAL FROM THREE SITES OF EVERGREEN HARDWOODS WAS SEPARATED BY SPECIES AND FORM OF MATERIAL (STEM WOOD AND BRANCHES WITH THE FOLIAGE) AND THEN WEIGHTED SEPARATELY FOR EACH SPECIES AND FORM. ALSO, FOR THIS MATERIAL THE STEM WOOD/BRANCHES AND FOLIAGE RATIO, WOOD/BARK RATIO AND THE PERCENT OF HUMIDITY WERE MEASURED. THE STEM WOOD OF FIVE SPECIES (QUERCUS ILEX, QUERCUS COCCIFERA, ARBUTUS UNEDO, ERICA ARBOREA, PHILLIREA MEDIA) AND MIXTURE OF BRANCHESFROM THE SAME SPECIES WERE PROCESSES INTO PARTICLEBOARD FURNISH USING AN INDUSTRIAL RING FLAKER. THE FURNISH WAS ANALYSED FOR ITS PARTICLE SIZE AND DISTRIBUTION, LENGTH, THICKNESS AND BULK DENSITY. A PART OF THIS FURNISH WAS SCREENED FOR REMOVAL OF THE VERY LARGE PARTICLES AND REDUCING THE AMOUNT OF FINES. ONE LAYER LABORATORY UREA-FORMALDEHYDE PARTICLEBOARDS WERE MADE A) USING THE UNSCREENED FURNISH SEPARATELY FOR EACH SPECIES, B) USING THE SCREENED FURNISH 1) SEPARATELY FOR EACH SPECIES, 2) ALL TOGETHER IN A MIXTURE AND 3) IN ADMIXTURES WITH FIR AND POPLAR. USING THE ABOVE MIXTURES THREE LAYER PARTICLEBOARDS WERE ALSO MADE USING SCREENED FURNISH FOR THE CORE AND FINES FOR THE SURFACE LAYERS. IN ADDITION TO THE ABOVE VENEERED BOARDS WERE MADE USING SCREENED FURNISH FOR THE CORE AND A POPLAR VENEER OF 2 MM IN THICKNESS FOR EACH SURFACE. ALL THE BOARDS WERE TESTED FOR DENSITY, I.B., M.O.R., THICKNESS SWELLING AND WATERABSORPTION. THE BENDING STRENGTH OF ALL BOARDS MADE WITH FURNISH FROM EVERGREEN HARDWOODS WAS VERY LOW. BOARDS MADE WITH ADMIXTURES OF FIR AND POPLAR HAD BENDING WITHIN THE STANDARDS. (ABSTRACT TRUNCATED)ΤΟ ΥΛΙΚΟ ΠΟΥ ΠΡΟΕΚΥΨΕ ΑΠΟ ΤΗΝ ΥΛΟΤΟΜΙΑ ΤΡΙΩΝ ΕΠΙΦΑΝΕΙΩΝ ΑΕΙΦΥΛΛΩΝ-ΠΛΑΤΥΦΥΛΛΩΝ ΔΙΑΧΩΡΙΣΘΗΚΕ ΚΑΤΑ ΕΙΔΟΣ ΚΑΙ ΜΟΡΦΗ (ΣΕ ΚΟΡΜΟΥΣ ΚΑΙ ΚΛΑΔΙΑ ΜΕ ΤΟ ΦΥΛΛΩΜΑ) ΚΑΙ ΖΥΓΙΣΘΗΚΕ ΚΑΘΕ ΚΑΤΗΓΟΡΙΑ ΧΩΡΙΣΤΑ. Σ'ΑΥΤΟ ΤΟ ΥΛΙΚΟ ΜΕΤΡΗΘΗΚΕ Η ΑΝΑΛΟΓΙΑ "ΞΥΛΩΝ/ ΚΛΑΔΙΩΝ ΚΑΙ ΦΥΛΛΩΜΑΤΟΣ", "ΞΥΛΟΥ/ΦΛΟΙΟΥ" ΚΑΙ Η ΠΕΡΙΕΧΟΜΕΝΗ ΥΓΡΑΣΙΑ. ΟΙ ΚΟΡΜΟΙ ΠΕΝΤΕ ΕΙΔΩΝ (Q. ILEX, Q. COCCIFERAD, PH. MEDIA, A. UNEDO ΚΑΙ E. ARBOREA) ΚΑΙ ΜΕΙΓΜΑ ΤΩΝ ΚΛΑΔΙΩΝ ΤΟΥΣ ΜΕΤΑΤΡΑΠΗΚΑΝ ΣΕ ΞΥΛΟΤΕΜΑΧΙΔΙΑ ΜΕ ΤΗΝ ΧΡΗΣΙΜΟΠΟΙΗΣΗ ΤΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΒΙΟΜΗΧΑΝΙΑΣ ΜΟΡΙΟΣΑΝΙΔΩΝ. ΣΤΑ ΞΥΛΟΤΕΜΑΧΙΔΙΑ ΕΓΙΝΕ ΚΟΚΚΟΜΕΤΡΙΚΗ ΑΝΑΛΥΣΗ, ΚΑΙ ΠΡΟΣΔΙΟΡΙΣΘΗΚΕ ΤΟ ΜΗΚΟΣ, ΠΑΧΟΣ ΚΑΙ Η ΧΩΡΙΚΗ ΠΥΚΝΟΤΗΤΑ ΤΟΥΣ. ΕΝΑ ΜΕΡΟΣ ΤΩΝ ΞΥΛΟΤΕΜΑΧΙΔΙΩΝ ΚΟΣΚΙΝΙΣΘΗΚΕ ΓΙΑ ΝΑ ΑΠΟΜΑΚΡΥΝΘΟΥΝ ΤΑ ΠΟΛΥ ΜΕΓΑΛΑ ΞΥΛΟΤΕΜΑΧΙΔΙΑ ΚΑΙ Η ΣΚΟΝΗ. ΣΤΟ ΕΡΓΑΣΤΗΡΙΟ ΚΑΤΑΣΚΕΥΑΣΘΗΚΑΝ ΜΟΝΟΣΤΡΩΜΕΣ ΜΟΡΙΟΣΑΝΙΔΕΣ ΜΕ ΟΥΡΙΑ ΦΟΡΜΑΛΔΕΥΔΗ Α) ΧΡΗΣΙΜΟΠΟΙΩΝΤΑΣ ΑΚΟΣΚΙΝΙΣΤΑ ΞΥΛΟΤΕΜΑΧΙΔΙΑ ΑΠΟ ΚΑΘΕ ΕΙΔΟΣ ΧΩΡΙΣΤΑ, Β) ΧΡΗΣΙΜΟΠΟΙΩΝΤΑΣ ΚΟΣΚΙΝΙΣΜΕΝΑ ΞΥΛΟΤΕΜΑΧΙΔΙΑ 1) ΑΠΟ ΚΑΘΕ ΕΙΔΟΣ ΧΩΡΙΣΤΑ, 2) ΜΕΙΓΜΑ ΑΠΟ ΟΛΑ ΤΑ ΕΙΔΗ ΚΑΙ 3) ΣΕ ΜΕΙΞΗ ΜΕ ΛΕΥΚΗ ΚΑΙ ΕΛΑΤΗ. ΕΠΙΣΗΣ ΚΑΤΑΣΚΕΥΑΣΘΗΚΑΝ ΤΡΙΣΤΡΩΜΕΣ ΜΟΡΙΟΣΑΝΙΔΕΣ ΧΡΗΣΙΜΟΠΟΙΩΝΤΑΣ ΚΟΣΚΙΝΙΣΜΕΝΑ ΞΥΛΟΤΕΜΑΧΙΔΙΑ ΣΕ ΔΙΑΦΟΡΕΣ ΜΕΙΞΕΙΣ ΓΙΑ ΤΗΝ ΜΕΣΑΙΑ ΣΤΡΩΣΗ ΚΑΙ ΠΟΛΥ ΛΕΠΤΟ ΥΛΙΚΟ (ΣΚΟΝΗ) ΓΙΑ ΤΙΣ ΕΠΙΦΑΝΕΙΕΣ. ΤΕΛΟΣ ΚΑΤΑΣΚΕΥΑΣΘΗΚΑΝ ΕΠΙΚΑΛΥΜΕΝΕΣ ΣΑΝΙΔΕΣ ΜΕ ΤΗΝ ΧΡΗΣΙΜΟΠΟΙΗΣΗΣΤΟΝ ΠΥΡΗΝΑ ΚΟΣΚΙΝΙΣΜΕΝΩΝ ΞΥΛΟΤΕΜΑΧΙΔΙΩΝ ΚΑΙ ΣΕ ΚΑΘΕ ΕΠΙΦΑΝΕΙΑ ΑΠΟ ΕΝΑ ΞΥΛΟΦΥΛΛΟ ΛΕΥΚΗΣ ΠΑΧΟΥΣ 2 MM. ΣΕ ΟΛΕΣ ΟΙ ΣΑΝΙΔΕΣ ΜΕΤΡΗΘΗΚΕ Η ΠΥΚΝΟΤΗΤΑ ΚΑΙ ΜΕΛΕΤΗΘΗΚΑΝ ΟΙ ΙΔΙΟΤΗΤΕΣ ΑΝΤΟΧΗ ΣΕ ΚΑΜΨΗ, ΑΝΤΟΧΗ ΣΕ ΕΓΚΑΡΣΙΟ ΕΦΕΛΚΥΣΜΟ, ΚΑΤΑ ΠΑΧΟΣ ΔΙΟΓΚΩΣΗ ΚΑΙ ΠΡΟΣΡΟΦΗΣΗ ΝΕΡΟΥ. (ΠΕΡΙΚΟΠΗ ΠΕΡΙΛΗΨΗΣ

Utilization Potential of Tree-of-Heaven Species Biomass—A Review

Climate change and the subsequent increase in global mean air temperature already present a significant impact on forest vegetation. Especially in the near future, several forest species are expected to be in danger of extinction or compelled to migrate to colder regions. Some common species will be replaced by highly climate-tolerant species, primarily exotic plants, among others. The tree of Ailanthus, or “tree-of-heaven”, as it is widely known, constitutes a rapidly growing plant, considered to be native to parts of China, while since the middle of the 18th century, it gradually spread to Europe and North America. This species demonstrates a preference for warmer, drier environments, although it can also survive in a variety of habitats and endure pollution of urban areas. It is a species with several uses, such as for animal feed, fuel, timber, pharmaceutical applications, etc., while its suitability for specialized applications of high-added-value is constantly being investigated. Its wood has a desirable appearance and characteristics that are comparable to those of other hardwood species of similar densities/weight. This article discusses some of the most important characteristics of Ailanthus wood and presents a comprehensive and constructive review of the chemistry, pharmacology, traditional and innovative uses, quality control, biological resistance, potential utilization in bioenergy and biofuels and wood products (e.g., wood-based panels, other advanced structure materials, etc.), use challenges and limitations, in order to contribute to the utilization potential assessment of this species biomass

SHORT NOTE INFLUENCE OF THERMAL TREATMENT ON MECHANICAL STRENGTH OF SCOTS PINE (PiNuS SylvESTRiS L.) WOOD

ABSTRACT In this study, mechanical properties of Scots pine wood (Pinus sylvestris L.) were determined after its thermal treatment at 200°C, for three different time periods of 4, 6 and 8 hours. Bending strength (MOR), modulus of elasticity (MOE), impact bending strength, compression strength and hardness in tangential and radial direction, which are properties of great significance for the strength and stability of wooden structures and furniture, were examined and compared to the corresponding untreated pine wood properties. Equilibrium moisture content (EMC) and density of treated and untreated specimens were also estimated