Usporedba vizualne procjene i izmjerene promjene boje površinski obrađenog drva

Staining of wood with various substances and processes is an important part of surface finishing of wood. Colour differences as a result of staining and of exposure of coloured wood during its utilisation are usually evaluated by instrumental measurements. However, the measurement results can show something else compared to what our naked eye can see. Due to inhomogeneity of wood, this discrepancy can be even greater in the case of finished surfaces. The aim of our research was to evaluate distinctions between visual perception and numerically determined colour differences on differently finished wooden surfaces, to get information at which starting point the colour difference becomes visible, and to establish whether it is related to the nature of the surface. We established that the visual assessment is influenced by many factors and that there is a correlation between visual and instrumental assessments. The colour difference ΔE* of 0.5 should be considered as a value when it starts to become visible, and at the value of 2.0, observers already considered the colour difference as a different colour. It was stated that we have some tolerance in perceiving the colour change. This tolerance is more expressed in the case of transparent coating systems.Premazivanje drva različitim sredstvima i primjenom različitih postupaka važan su dio površinske obrade drva. Promjene boje kao rezultat premazivanja i izlaganja obojenog drva tijekom njegove uporabe obično se mjere uređajima. Međutim, izmjereni rezultati pokazuju nešto sasvim drugo od onoga što se vidi ljudskim okom. Kad je riječ o površinskoj obradi drva, razlike između izmjerenih rezultata i onoga što se vidi ljudskim okom mogu se povećati zbog nehomogenosti drva. Cilj istraživanja bio je procijeniti razlike između vizualne procjene i izmjerene promjene boje na površinski obrađenom drvu primjenom različitih tehnika kako bi se utvrdila vrijednost pri kojoj je promjena boje vidljiva te kako bi se utvrdilo ovisi li ona o vrsti površine. Ustanovili smo da na vizualnu procjenu promjene boje utječe velik broj čimbenika i da postoji veza između vizualne procjene i izmjerenih vrijednosti promjene boje. Promjena boje ΔE* od 0,5 vrijednost je pri kojoj promjena boje postaje vidljiva, a promjenu boje od 2 promatrači vide kao različitu boju. Uočeno je da postoji određena tolerancija u percepciji promjene boje, koja je veća pri procjeni promjene boje prozirnih sustava premaza

Površinska obrada nekih invazivnih vrsta drva

Due to their strong renewal power, the invasive tree species are spreading rapidly, especially in abandoned agricultural and forest areas and along traffic routes and water courses. One way of their restriction is the promotion of their use. In our research, we investigated surface finishing of wood of five selected invasive species in Slovenia, Box elder (Acer negundo L.), Black locust (Robinia pseudoacacia L.), Horse-chestnut (Aesculus hippocastanum L.), Honey locust (Gleditsia triacanthos L.) and Chinese sumac (Ailanthus altissima (Mill.) Swingle), and compared it with the finishing of the European beech (Fagus sylvatica L.) wood. For coatings, we selected one-component waterborne finish on acrylate-polyurethane basis, one-component solventborne finish on polyurethane basis and tung oil as a natural finish. Several surface properties were investigated. We proved that surface hardness, resistance to impact and adhesion were very much related to interactions between the coating and the substrate, while resistance to cold liquids was only dependant on the type of the finish. It was also shown that, in general, finishing of woods of selected invasive tree species was not problematic. The only exception was Black locust wood on which tung oil cured very slowly.Invazivne vrste drva brzo se šire zbog izrazito jakog svojstva obnavljanja, posebice na zapuštenim poljoprivrednim i šumskim površinama te uz prometnice i vodotokove. Jedan od načina ograničavanja njihova širenja jest poticanje uporabe njihova drva. U ovom smo istraživanju proučavali površinsku obradu pet invazivnih vrsta drva u Sloveniji: negundovca (Acer negundo L.), bagrema (Robinia pseudoacacia L.), divljeg kestena (Aesculus hippocastanum L.), gledičije (Gleditsia triacanthos L.) i pajasena (Ailanthus altissima (Mill.) Swingle), u usporedbi s površinskom obradom bukovine (Fagus sylvatica L.). Kao premazni materijali upotrijebljeni su jednokomponentni vodeni lak na bazi poliakrilata i poliuretana, jednokomponentni otapajući poliuretanski lak i tungovo ulje kao prirodni premazni materijal. Pritom je ispitivano nekoliko svojstava površine. Dokazano je da tvrdoća površine, otpornost na udarce i adhezija izrazito ovise o međudjelovanju premaza i podloge, a otpornost na hladne tekućine ovisi samo o vrsti premaza. Također je dokazano da površinska obrada promatranih invazivnih vrsta drva nije problematična. Izuzetak je drvo bagrema, na kojemu se tungovo ulje vrlo sporo suši

Pojačana otpornost na abraziju premazanih iverica prethodno obrađenih atmosferskom plazmom

This study aims to investigate the influence of atmospheric plasma treatment on the abrasion resistance of particleboards, as an example of a wood-based material, coated with a waterborne finish. The treatment of the substrate, prior to coating application, using a floating-electrode dielectric barrier discharge (FE-DBD) plasma, resulted in an enhanced abrasion resistance of the coated particleboards in comparison to the untreated ones during the abrasion test with a duration of 200 revolutions. This finding was related to lower contact angles of water and coating after treatment with plasma and greater hardness of the coating on the treated substrates. The micrographs of the sample cross sections recorded with scanning electron microscope showed differences in the amounts of remained coating on the abraded areas. Investigation with attenuated total reflection Fourier transform infrared spectroscopy revealed that treatment of the substrate with plasma did not affect the chemical composition nor the curing and structure of the later applied coating. Further studies should be performed to determine the resistance properties of such surface systems to other impacts.Cilj ovog rada bio je istražiti utjecaj atmosferske plazme na otpornost iverica na abraziju, kao primjer materijala na bazi drva premazanoga vodenim premazom. Tijekom ispitivanja abrazije u trajanju od 200 ciklusa obrada iverica uz pomoć plazme (FE-DBD) prije nanošenja premaza rezultirala je poboljšanom otpornošću premazanih iverica na abraziju u usporedbi s neobrađenom ivericom. Rezultat istraživanja povezan je s nižim kontaktnim kutom vode i premaznog materijala nakon obrade iverica plazmom i s većom tvrdoćom premaza na podlozi obrađenoj plazmom. Mikrografi je presjeka uzorka dobivene pretražnim elektronskim mikroskopom pokazale su razlike u količini preostalog premaza na površinama ispitanima na otpornost na habanje. Ispitivanje infracrvenom spektroskopijom uz prigušenu totalnu refleksiju pokazalo je da obrada podloge plazmom nije utjecala na kemijski sastav ni na otvrdnjavanje i strukturu kasnije nanesenog premaza. Potrebno je provesti daljnja ispitivanja kako bi se dodatno utvrdila otpornost takvih površinskih sustava

Prof. Dr. Katarina Čufar received the Zois Prize for important achievements and the Golden Plaque of the University of Ljubljana

At the end of 2020, Prof. Dr. Katarina Čufar received two prestigious awards: the Zois Prize for important scientific research achievements in the development of dendrochronology and wood science, which is a state award of the Republic of Slovenia, and Golden Plaque from the University of Ljubljana for outstanding scientific research, exemplary teaching and achievements in enhancing the university’s reputation. We briefly introduce the prize-winner and her work

Dr. Jure Žigon je prejel Jesenkovo nagrado Biotehniške fakultete UL za najboljšega diplomanta doktorskega študija 3. stopnje 2021

Jesenkove nagrade Biotehniške fakultete UL so najvišja priznanja za pedagoške, raziskovalne in strokovne dosežke ter za gospodarski in splošni družbeni napredek na področju biotehniških ved v Sloveniji. Biotehniška fakulteta jih podeljuje že vse od leta 1973, med njimi tudi Jesenkovo nagrado za najboljšega diplomanta doktorskega študija. Za leto 2021 je to nagrado na slovesnosti v marcu 2022 prejel asist. dr. Jure Žigon, ki je na Oddelku za lesarstvo BF zaposlen kot samostojni strokovni delavec

Prof. Dr. Katarina Čufar received the Jesenko Lifetime Achievement Award

In March 2021, Prof. Dr. Katarina Čufar received the Jesenko Lifetime Achievement Award, the most prestigious prize of the Biotechnical Faculty, University of Ljubljana. This is the third award for Katarina Čufar within just a few months, as at the end of 2020 she also received the Golden Plaque from the University of Ljubljana and the Zois Prize of the Republic of Slovenia for significant scientific achievements and exemplary teaching

Prof. dr. Primož Oven – prejemnik Zlate plakete Univerze v Ljubljani

Na Univerzi v Ljubljani (UL) je med 28. novembrom in 2. decembrom 2022 potekal Teden univerze in tudi letos, ob 103. rojstnem dnevu univerze, so bili predstavljeni najodličnejši raziskovalni dosežki, podeljeni častni nazivi, plakete, nagrade in priznanja vsem, ki so pripomogli, da je Univerza v Ljubljani iz leta v leto boljša. Na Oddelku za lesarstvo Biotehniške fakultete UL smo zelo ponosni, da je na slavnostni seji Senata Univerze v Ljubljani 29. 11. 2022 Zlato plaketo prejel tudi naš sodelavec, prof. dr. Primož Oven, vodja Katedre za kemijo lesa in druge lignocelulozne materiale. Prof. Oven je mednarodno uveljavljen raziskovalec in pedagog na področju proučevanja zvez med funkcijami, strukturami, kemizmom in lastnostmi lesa, biorafinacije ter valorizacije lesne biomase s poudarkom na pridobivanju in uporabi nanoceluloze in lesnih ekstraktivov. V akademskem in gospodarskem okolju promovira trajnostno izrabo lesa v krožnem biogospodarstvu in skrbi za ugled UL doma in v tujini