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Viskoelastično toplotno zgoščen les (Viscoelastic Thermal Compressed wood, VTC les) ima zaradi visoke gostote in s tem izboljšanih mehanskih lastnosti velik potencial pri razvoju visokokakovostnih lesnih produktov. Širšo uporabo omejuje v največji meri povratek tlačne deformacije, do katerega pride ob izpostavitvi VTC lesa območjem s povišano vlažnostjo. Termična modifikacija pa je eden od načinov, s katerim lahko izboljšamo dimenzijsko obstojnost lesa in odpornost na lesne glive. V diplomski nalogi smo se osredotočili na dimenzijsko stabilnost tlačne deformacije VTC lesa. Vzorce smrekovega in bukovega lesa, ki so bili predhodno zgoščeni po postopku VTC, in kontrolne nezgoščene vzorce smo termično modificirali pri različnih temperaturah (190 °C, 200 °C, 210 °C in 220 °C). Obstojnost tlačne deformacije smo preverili z namakanjem v vodi. Postopek namakanja smo ponovili v petih ciklih, kjer smo ugotovili, da je povratek tlačne deformacije odvisen od temperature termične modifikacije in lesne vrste. Ugotovili smo, da je obstojnost VTC lesa neposredno povezana z izgubo mase, nastale med postopkom termične modifikacije. Pri termični modifikaciji pri najvišji uporabljeni temperaturi, t. j. 220 °C, pride do večje izgube mase lesa, pri čemer dosežemo boljšo obstojnost in zmanjšamo povratno tlačno deformacijo ter s tem izboljšamo dimenzijsko stabilnost VTC lesa. Viscoelastic thermal compressed (VTC) wood has due to the high wood density and thus improved mechanical properties great potential in the development of high-quality wood products. Its wider utilization is limited by set recovery of compressive deformation, which occurs when VTC wood is exposed to environment of increased humidity. Thermal modification is one of the process which can improve the dimensional stability of wood and resistance to fungal decay. In this thesis the problem of set recovery of compressive deformation was studied. Samples of spruce and beech wood, which were previously densified by the VTC process, were thermally modified with a thermal modification process at different temperatures (190 °C, 200 °C, 210 °C, and 220 °C). Set recovery of compressive deformation was examined after 5 water soaking cycles. It was found that set recovery of compressive deformation depended on the temperature of thermal modification and wood species. It was determined that stability of compression deformations of the VTC wood depends on the level of thermal modification. Thermal modification at temperature 220 °C caused significant mass loss, better stability, and reduced set recovery of compressive deformation, and thus improved the properties of VTC wood.

V skladu s standardnimi metodami SIST EN 113, SIST EN 152-1 ter nestandardno, tako imenovano obrnjeno metodo po Van Acker-ju, smo preverili odpornost nepremazanega, v vročem olju modificiranega lesa na prave razkrojevalke in premazanega, v vročem olju modificiranega, lesa na glive modrivke. Ugotovili smo, da je modifikacija lesa učinkovit postopek za zaščito lesa, prav tako pred pravimi razkrojevalkami kot pred glivami modrivkami. Premazna sredstva dodatno zaščitijo les pred okužbo z glivami modrivkami, zato je površinska obdelava modificiranega lesa priporočljiva. The resistance of uncoated, oil heat treated wood to wood rotting fungi and that of coated, oil heat treated, wood to blue stain fungi were examined. Wood resistance was examined according to the SIST EN 113, and SIST EN 152-1 standard method, so as using a non-standard, so called reverse exposure method named ofter Van Acker. It was found out that the oil heat treatment is an effective process protecting wood from rotting so as from blue stain fungi. Because of surface coatings being very helpful as additional protection of wood against infection of blue stain fungi the surface treatment of oil heat treated wood is recommendable.

V podjetju, ki izdeluje kuhinjsko pohištvo, želijo v proizvodnjo vključiti modificiran les, ker je dimenzijsko stabilnejši. S postopkom modifikacije lahko vplivamo tudi na barvo, zato jim modificiranega lesa ne bi bilo treba lužiti. Pri tem pa je pomembno, da so klasični in vodni premazni sistemi kompatibilni z modificiranimi podlagami ter kako lastnosti modificiranega lesa vplivajo na lastnosti površinskega sistema. Na nemodificiranem ter v vakuumu termično (pri temperaturah 150 °C in 200 °C) modificiranem hrastovem lesu, smo preizkušali nekatere lastnosti: debelino, oprijemnost, odpornost proti udarcem, razenju in odpornost robov proti vodi, utrjenih filmov vodnega in poliuretanskega laka ter barvo in sijaj. Ugotovili smo, da je vodni lak slabo odporen proti mehanskim poškodbam ter da vrsta podlage močno vpliva tako na debelino utrjenega filma, na sijaj, kot tudi na odpornostne lastnosti površinskega sistema. Z višanjem temperature modifikacije se te lastnosti slabšajo, zmanjša pa se tudi debelina utrjenega filma. Najslabše lastnosti smo ugotovili pri preizkušancih, modificiranih pri 200 °C, pozitivno je izstopala le odpornost robov proti omočitvi z vodo. Kitchen furniture producer wants to introduce thermally modified wood into their regular production. Thermal modification of wood increases its dimensional stability and influences its colour, so there would be no need to stain it. However, there are questions, whether the classical waterborne coating systems are compatible with the modified substrates, and how the properties of modified wood influence characteristics of the system. Some properties: thickness, adhesion, resistance against impact and scratching, and resistance of edges against water of strengthened films of waterborne and polyurethane coatings were tested on untreated and in vacuum thermally modified (temperatures: 150 °C and 200 °C) oak wood colour and gloss. It was found out that waterborne coatings showed low resistance against mechanical injuries, the type of the substrate influenced the thickness of strengthened film strongly, so as gloss, and properties of surface system. These properties get worse with too high a temperature of modification, also thickness of strengthened film reduces. The worst properties were found in wood samples, modified at 200 °C, the only exception being the resistance of edges against watering.

Večina zaščitnih pripravkov za les predstavlja potencialno nevarnost za okolje in človeka, tako med postopkom zaščite, z uporabo lesa in obdelavo kot tudi popreteku življenjske dobe zaščitenega lesa. Zato si v zadnjem času prizadevamo za razvoj novih okolju prijaznejših postopkov zaščite. Ena od možnih rešitev je modifikacija lesa. Na vzorcih, modificiranih z različnimi silicijevimi spojinami, ki so jih pripravili na Inštitutu za biologijo in tehnologijo lesa v Göttingenu (Nemčija), smo opravili test v skladu s privzetim evropskim standardom SIST EN 152/2. Vzorci so bili izpostavljeni delovanju suspenzije spor gliv modrivk Aureobasidium pullulans in Sclerophoma pithyophilla. Ugotovili smo, da modifikacija s silicijevimi spojinami lesa ni zaščitila pred modrenjem, z izjemo Silikonata 1, ki je preprečil obarvanje vzorcev z glivami modrivkami. Most of the wood preservatives represent a potential danger for environment and human beings, while wood protecting, treating, using, and decaying. Therefore, lately, there is a tendency to develop a new environment friendly procedures to protect it. One of the possibilities is a modification. The specimens, modified with various silicon compounds, prepared at the Institute of Wood Biology and Technology in Göttingen (Germany), were tested then at faculty, in accordance with the SIST EN 152/2 standard instructions, and exposed to the suspension of blue stain spores Aureobasidium pullulans and Sclerophoma pithyophilla. It was found out that the modification with silicon compounds did not protect wood against blue stain fungi, with the exception of Siliconat 1, which prevented wood colouring.

Les je, kot naravni material, vnetljiv in gorljiv. Ker ga je zato treba ustrezno zaščititi proti gorenju, smo preizkušali najnovejše postopke termične modifikacije lesa ter impregnacijo z okolju prijaznejšimi sredstvi kot so borove učinkovine. Ugotoviti smo želeli, kakšna je gorljivost termično modificiranega lesa. Les smo impregnirali z 1, 5 ter 10 % vodno raztopino Topbora. Impregniran kot neimpregniran les smo nato še dodatno termično modificirali v vakuumu pri temperaturi 150, 170, 190, 210, 230 °C. Za testiranje gorljivosti lesa smo uporabili modificirano ameriško metodo ASTM: E69-50 (1965). Rezultati so pokazali, da so kontrolni vzorci v 4,28 min izgubili 75 % lesne mase. Pri modificiranem lesu pa smo najboljši rezultat zabeležili pri temperaturi modificiranja 210 °C ter 10 % vodno raztopino Topbora, kjer so vzorci v 4,16 min izgubili le 32 % mase. Ugotovili smo, da se gorljivost modificiranega lesa zniža samo z dodatkom Topbora. Pri neimpregniranem modificiranem lesu je odstotek izgube lesne mase nižji ali enak kot pri kontrolnih vzorcih. Wood is a natural material, inflammable and combustible material. Considering this fact it is necessary to utilise proper flame retardants. The latest procedures of thermal modification of wood and impregnation with environmentally friendly biocides such as boron compounds were tested. Our purpose was to find out the combustibility of thermally modified wood. Wood was impregnated with 1, 5 and 10 % Topbor based aqueous solutions. The impregnated so as not impregnated wood was then further thermally modified in the vacuum at 150, 170, 190, 210 and 230 °C. For testing, a modified American method ASTM E 69-50 (1965) was utilised. Control samples lost 75 % of wood mass in 4.28 min. At the modified wood, the best results are reported after modification of samples impregnated with 10 % Topbor aqueous solution at 210 °C, where the samples lost only 32 % of the weight in 4.16 min. It was found out that the burning behaviour of the modified wood was reduced only by the addition of boron. When not impregnated, the percentage of loss of wood mass is comparable to the control specimens.

Vzorce rdečega bora in bukve smo modificirali s sredstvi na osnovi silicija. Uporabili smo več različnih raztopin. Da bi ugotovili fungicidno odpornost, smo vzorce izpostavili trem lesnim glivam: kletni gobi (Ciniophora puteana), hišni gobi (Poria placenta) in pisani ploskocevki (Trametes versicolor). Ugotavljali smo tudi odpornost na mehko trohnobo, bakterije in modul elastičnosti lesa. Najmanjša izguba modula elastičnosti po modifikaciji in osmih tednih izpostavljenosti zemlji je bila pri borovih vzorcih, modificiranih z nerazredčenim sredstvom metiltrietoksisilana pri bukvi pa pri vzorcih, modificiranih z nerazredčenim sredstvom tetraetoksisilana. Z vodnim steklom pa smo opravili tudi test izpiranja po EN 84 in skušali ugotoviti, ali čas utrjevanja vpliva na odpornost na glive. Mikroskopske raziskave so pokazale tipične znake trohnob. Ugotovili smo, da sta modifikacijski sredstvi (SMK2100 (100 %) in HS2090 (20 %) vidno prisotni v celicah. Mini-blok test z glivama Coniophora puteana in Poria placenta ni uspel, s Trametes versicolor pa je pokazal, da je najbolj odporno modifikacijsko sredstvo PTEO tu je bila izguba mase vzorcev manjša od 10 %. Pine and beech samples were modified using various silicon chemicals. To find out fungicidal resistance the samples were exposed to 3 wood fungi: Coniophora puteana, Poria placenta and Trametes versicolor. Resistance to soft rot, bacteria and dynamic module of elasticity were studied also. After the modification and 8 weeks long exposition to soil beds, the smallest loss of elasticity module was found at pine samples, modified with MTES (100 %) and with TEOS (100 %) at beech. To find out whether the fixation time has any influence on fungi, EN 84 washing out test with water glass was performed. Microscopic research showed typical signs of either soft, brown or white rot. Modification means SMK2100-100 % and HS2090-20 %) were observed in the cells. Mini-block test with Coniophora puteana and Poria placenta did not succeed. The test with Trametes versicolor proved PTEO to be the most resistant modification means, the mass loss of the samples was less than 10 %.

Les je zelo nagnjen k krčenju in nabrekanju. Da bi ga ustrezno stabilizirali, smo ga termično modificirali. Ugotavljali smo, kako vpliva termična modifikacija na dimenzijsko stabilnost in odpornost proti glivam modrivkam. Modifikacijo hrastovega in bukovega pulta smo opravili v vakuumu pri temperaturi 170 °C in 200 °C. V prvem primeru smo modificirali že zlepljen pult, v drugem pa elemente lesa, ki smo jih kasneje zlepili v pult. Dimenzijsko stabilnost smo preizkušali tako, da smo vzorce namakali v vodi in nato spremljali nabrekanje. Za ocenjevanje odpornosti proti glivam modrivkam smo uporabili standardizirano metodo SIST EN 152. Ugotovili smo, da termična modifikacija poveča dimenzijsko stabilnost lesa že pri 170 °C, še izraziteje pa pri 200 °C. Večjo dimenzijsko stabilnost smo ugotovili pri kasneje zlepljenih pultih. Modifikacija je povečala odpornost pulta proti glivam modrivkam. Pri hrastu je bila bolj učinkovita, saj je preprečila pomodrelost že pri 170 °C, pri bukovini pa se je odpornost na modrivke pokazala pri temperaturi modifikacije 200 °C. Wood is very vulnerable to shrinkage and swelling. To stabilise it accordingly, we have modified it thermally. We wished to determine the impact of thermal modification on the dimensional stability and resistance to blue stain fungi. Modification of oak and beech panel was performed in a vacuum at a temperature of 170 °C and 200 °C. In 1st case, we modified a previously glued panel. In 2nd case, we modified the wooden elements and glued them together subsequently. Dimensional stability was tested by soaking the samples in water and monitoring the swelling. To assess resistance to blue stain fungi we used a standardised method SIST EN 152. We established that thermal modification increased the dimensional stability of wood already at 170 °C, but even more explicitly at 200 °C. Greater dimensional stability was observed in panels glued together later. The modification increased the resistance of panels against blue stain fungi. In the case of oak wood, it was more effective as it prevented blue staining already at 170 °C, and in the case of beech wood, the resistance to blue stain fungi was indicated at 200 °C.