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

Uporaba naravnih olj za površinsko zaščito lesa navadne bukve

Different natural drying oils were used for surface finishing of common beech wood (Fagus sylvatica L.). Surface performances and properties of the oiled surfaces were investigated according to the standard tests. Drying time, colour and gloss changes, uptake of oils into wood and uptake of liquid water into oiled wood, were determined, and the wettability of oiled wood surfaces was investigated by determination of the apparent contact angles of water. The results of the standard resistance tests showed that tung oil, the commercial decking and linseed oil had the best water repellent and protective properties. Worse properties were determined for those surfaces finished with walnut, hemp and coconut oils

Resistance of polylactic acid/nanofibrillated cellulose composite to scratching

The aim of the study was to prepare a bionanocomposite based on polylactic acid (PLA) with the addition of nanofibrillated cellulose (NFC) as a reinforcement component. For the production of the composite we used unmodified and acetylated NFC (A_NFC). Freeze-dried NFC was acetylated in a heterogeneous system with acetic anhydride in dimethylformamide (DMF) in the presence of pyridine as a catalyst. The success of the acetylation was determined by FT-IR spectroscopy. PLA films were prepared with the addition of 2.5%, 5% and 10% of unmodified and acetylated NFC. The focus of this research was the impact of the NFC additive on the transparency and on the resistance of the bionanocomposite to scratching. The transparency of the bionanocomposite film was measured using UV-Vis spectrophotometry, and the resistance of the films to scratching was evaluated with a scratch test. The optimal amount of NFC and A_NFC added to the polymer PLA to achieve better resistance of the bionanocomposite to scratching was determined. The best resistance of the prepared bionanocomposite to scratching was achieved by the addition of a 2.5% A_NFC to the PLA polymer, which also has minimal reduced transparency with respect to the PLA film. With the highest addition of A_NFC to the PLA polymer, bionanocomposite films with minimal reduction of transparency were obtained

Gallery-pedagogical activities and fine arts in the first three years of primary school

This article discusses the integration of pupils of the first educational period of the primary school in the gallery-pedagogical activities within the regular classes. In a qualitative study, we examined the extent to which these students are involved in the activities of the gallery, how the planning and the execution of visiting the curators-educators is going, how many works of art of the current exhibition the students see, and in which way they are presented to them. We were also interested in the reactions of the students on the works of art and their sense of self-initiative. The study has shown the importance of museums and galleries, where students have the opportunity to experience the works of art in an authentic gallery area. This way the students experience art differently, they estimate it, and think about it. Having developed the museum pedagogy or pedagogical activities, the curators-educators can contribute a lot to accepting art among the youngest students

Lastnosti površinskih premazov v odvisnosti od njegovih interakcij s termično modificiranim lesom

V Evropi so se razvili različni postopki termične modifikacije, za katere je značilno, da povečajo dimenzijsko stabilnost in biološko odpornost lesa. Odpornost termično modificiranega lesa proti fotodegradaciji pa ostaja bolj ali manj nespremenjena in površinska obdelava takega lesa je še vedno potrebna. V raziskavi smo proučili kompatibilnost devetih različnih premazov s termično modificiranim lesom rdečega bora (Pinus sylvestris L.). Z enoletnim staranjem v naravnih razmerah smo ugotovili, da se trajnost filmov premazov poveča, če so premazi naneseni na termično modificiran les. Ugotovili smo, da je razlog za to v spremenjenih lastnostih termično modificiranega lesa. Ta ima nižjo ravnovesno vlažnost, zmanjšano sposobnost absorpcije tekoče vode, povečano dimenzijsko stabilnost, boljšo UV-obstojnost in biološko odpornost, kot tudi boljše omakanje s premazi in globljo penetracijo premazov. Prav tako smo ugotovili, da so se sistemi s premazi na vodni osnovi po enoletnem staranju slabše izkazali kot sistemi s premazi na osnovi organskih topil, saj so bolj plesneli, filmi premazov pa bolj pokali. Dodajanje fotostabilizatorjev transparentnim premazom se je odrazilo v zmanjšanju luščenja in pokanja filmov premazov. Pigmentirani sistemi so bili v primerjavi s transparentnimi sistemi odpornejši. Rezultati večje trajnosti premaznih sistemov na termično modificiranem lesu so pokazali, da prilagoditev obstoječih premazov za les za uporabo na termično modificiranem lesu ni potrebna.Various heat treatment processes for wood modification have been developed in Europe, resulting in increase of dimensional stability and resistance to biological attack of wood. However, resistance of thermally modified wood against photodegradation remains almost the same and surface finishing of modified wood is still needed. The aim of research was to study compatibility of nine different coatings with thermally modified Scotch pine wood (Pinus sylvestris L.). One-year natural weathering test showed that the durability of coatings was increased when applied on thermally modified wood. This finding was explained by the changed characteristics of thermally modified wood, which, in comparison with unmodified wood, showed lower equilibrium moisture content, lower liquid water permeability, increased dimensional stability, better UV stability and resistance to blue stain fungi. Better wetting of thermally modified wood with coatings and deeper penetration of coatings into modified wood were observed as well. It was also established that after one year of weathering the systems with waterborne coatings showed inferior performance compared to the systems with solventborne finishes, exhibited by film cracking and moulding of the whole system. The addition of photostabilizers into the transparent coating formulation resulted in a decrease of flaking and cracking of the coating. Compared to the transparent systems, the pigmented systems proved as superior. The results of better performance of the systems thermally modified wood - coating compared to the systems unmodified wood - coating showed that adjustment of existing commercial coatings for use on thermally modified wood is not needed

Assessment of the stain penetration in wood

Po postopku luženja z vodnim lužilom so v lesnoobdelovalnem podjetju naleteli na problem različnega nabreka posameznih letvic znotraj lepljenega elementa. Zaradi tega smo obstoječe lužilo poskušali modificirati na ta način, da bi zmanjšali njegovo penetracijo v les. Pripravili smo 15 novih formulacij, še pred tem pa smo morali razviti hitro, enostavno in zanesljivo metodo za določanje globine penetracije lužila v les. Ugotovili smo, da so štirje novi pripravki penetrirali signifikantno manj od izvornega vodnega lužila. Le-te bomo preskusili tudi v industrijskem merilu. Dobljene razlike v globini penetracije preskušenih pripravkov so izkazale, da je novo razvita metoda zanesljiva. Kljub temu pa jo bomo v naših nadaljnjih raziskavah poskušali izboljšati. Prav tako bomo proučili vpliv vlažnosti lesa pred luženjem na globino penetracije lužila.During the staining a company, producing wood furniture, encountered a problemof uneven swelling of small boards in glued elements. Therefore we tried to modify the used stain in the way that it would penetrate less into wood. We prepared 15 modified formulations of the waterborne stain, but firstly, we had to develop a simple, quick and reliable method for determination of the stain penetration into the wood. We have found that four modified waterborne stain formulations penetrated significantly less than the original one. Their performance on the industrial scale will be evaluated by further tests. The observed differences between penetration depths of the tested formulations proved that the new method is reliable. However, in order to improve the method, some further investigations will be carried out. We also intend to investigate the influence of wood moisture content on the penetration of the stain

Hardwood polyoses

Prispevek obravnava lesne polioze (hemiceluloze) listavcev. Le-te so poleg celuloze eden od obnovljivih naravnih organskih snovi. Lesovi listavcev imajo drugačno vsebnost in sestavo lesnih polioz kot iglavci. Delež polioz v lesu listavcev se giblje do 40 %. Predstavljajo zanimivi vir kemikalij: ksiloze, ksilitola, furfurala, hidroksimetilfurfurala, levulinske kisline in drugih. Za uspešno uporabo lesnih polioz je vsekakor potrebno izredno dobro poznavanje njihove kemijske zgradbe.The article studies hardwood polyoses (hemicelluloses), being one of renewablenatural organic materials, next to cellulose. Hardwood polyoses differ from softwood ones with regard to their content and compositiontheir portion in hardwoods being up to 40%. Polyoses could be converted to primary chemicals: xylose, xylitol, furfural, hydroxymethylfurfural, levulinic acid, etc. To use wood polyoses successfully we have to understand their chemical structure well