Design and manufacturing of organic shape furniture

Wooden furniture of organic shapes was mostly handmade in the past, each piece was almost unique, since the manufacturing processes did not allow repeatability and larger quantity production of the same products. Today, modern 3D modelling software leads to completely different prospective in wooden furniture design and production. It enables modelling of any kind of shape, based on ideas, natural shapes, even 3D scanned existing shapes, etc. Furthermore, prototypes can be 3D printed. This enables that visual presentation of designed form is made in real. Based on the printed forms virtual models can be improved leading to the final sophisticated model. Additionally, during design process the best construction details can be made to improve material efficiency and manufacturing time. Final product can be than made on CNC machines, enabling reproduction of the same product of desired shape in chosen quantities

Utjecaj količine otapala u utekućenom drvu i dodatka kondenziranog tanina na kvalitetu vezanja

Liquefied wood (LW) is a promising natural material that can be used as a part of the adhesive formulation. However, adhesive bonds made of LW only, have low durability. The aim of this study was, therefore, to increase the durability of adhesive bonds containing LW. LW was obtained with liquefaction of black poplar wood in ethylene glycol (EG) as the solvent and sulphuric acid (SA) as the catalyst. An optimal time of 120 minutes and a wood/EG mass ratio of 1:3 was defi ned for liquefaction at 180 °C. After liquefaction, the EG was evaporated in order to achieve a low solvent content LW with a fi nal mass ratio of 1:1. A hydroxyl number for 1:3 and 1:1 LW was determined in order to examine the reduction of hydroxyl groups. Four different adhesive mixtures were prepared: LW with a mass ratio of 1:1 (LW1:1 ), LW with a mass ratio of 1:3 (LW1:3 ), LW with a mass ratio of 1:1 and added condensed tannin (CT) (LW1:1 /CT), and LW with a mass ratio of 1:3 and added CT (LW1:3 /CT). The solid beech wood lamellas, which were bonded with these adhesive mixtures, were tested directly after bonding, and later on, after 7, 30 and 50 days. The test results indicated greater bonding shear strength in the case of LW1:1 compared to LW1:3. The addition of CT did not contribute to essentially higher shear strength values. The adhesive mixtures LW1:1 and LW1:1 /CT (uncured and cured) were analyzed using FT-IR spectroscopy. No significant differences were observed between the cured LW1:1 and the LW1:1 /CT samples.Utekućeno drvo (LW) perspektivan je prirodni materijal koji može biti upotrijebljen kao tvar za izradu ljepila. Međutim, vezivna ljepila napravljena samo od utekućenog drva imaju malu trajnost. Stoga je cilj provedenih istraživanja bio povećati trajnost vezivnih ljepila koja sadržavaju LW. U provedenim je istraživanjima LW dobiven utekućenjem drva topole u etilen glikolu (EG) kao otapalu i sumpornoj kiselini (SA) kao katalizatoru. Definirano je optimalno vrijeme utekućenja od 120 minuta i maseni omjer drvo:EG u iznosu 1:3 za utekućenje pri temperaturi 180 °C. Nakon utekućenja EG je ishlapljen da bi se postigao nizak sadržaj otapala u LW-u s konačnim masenim omjerom 1:1. Utvrđen je hidroksilni broj za LW s omjerom 1:3 i LW s omjerom 1:1 da bi se ispitalo smanjenje broja hidroksilnih skupina. Pripremljene su četiri različite mješavine ljepila: LW s masenim omjerom 1:1 (LW1:1 ), LW s masenim omjerom 1:3 (LW1:3 ), LW s masenim omjerom 1:1 te dodanim kondenziranim taninom (CT) (LW1:1 /CT), i LW s masenim omjerom 1:3 i dodanim CT-om (LW1:3 /CT). Lamele od bukovine lijepljene su navedenim mješavinama ljepila i ispitane odmah nakon lijepljenja, zatim nakon 7, 30 i 50 dana. Rezultati testa pokazali su veću smicajnu čvrstoću vezanja u slučaju LW1:1 u odnosu prema LW1:3 . Dodavanje CT-a nije znatno pridonijelo većoj smicajnoj čvrstoći. Mješavine ljepila LW1:1 i LW1:1 /CT (nesušene i osušene) analizirane su FT-IR spektroskopijom. Nisu zapažene signifi kantne razlike između osušenih uzoraka LW1:1 i LW1:1 /CT

Možnosti uporabe lesa v dodajalnih tehnologijah (3D-tiskanju)

Additive manufacturing technologies have developed greatly over the last decade in terms of technology and printing materials. Special emphasis is placed on the development of cheaper materials that are derived from natural sources, without the release of harmful substances during the manufacturing process, with the possibility of using waste materials and recycling after service life. Wood or wood residues are among the potential raw materials that could be used for 3D printing in combinations with natural and synthetic polymers. It is anticipated that, with the development of additive technologies, the use of wood will also expand to the area of structural elements, such as in the construction of prefabricated houses. A review of publications on the topic of 3D printing with natural raw materials with an emphasis on wood biomass and technologies, where the use of wood particles is possible, was made

Influence of thermal modification of wood on curing of adhesives and bond performance

Proučevali smo vpliv temperature termične modifikacije na utrjevanje in kakovost lepilnih spojev. Uporabili smo les smreke, ki je bil termično modificiran pri temperaturah 150, 170, 190, 210 in 230 °C ter različna lepila: fenol-formaldehidno (FF) za vroče lepljenje ter tri lepila za hladno lepljenje: polivinilacetatno (PVAc), poliuretansko (PU) ter melamin-urea- formaldehidno (MUF). Utrjevanje lepil smo spremljali z merjenjem reoloških lastnosti z reometrom pri čemer smo namesto standardnih aluminijastih diskov uporabili diske iz termično modificiranega lesa z različno stopnjo modifikacije ter z različnimi vlaţnostmi. Uporabili smo oscilatorni test z "multiwave" tehniko merjenja. Ugotovili smo, da so PVAc, PU ter MUF lepila utrjevala počasneje glede na stopnjo termične modifikacije lesa, vendar so bili razlogi različni. PVAc in MUF lepili sta utrjevali počasneje zaradi slabše absorpcije vode v modificiran les, PU lepilo pa zaradi niţje vlaţnosti modificiranega lesa. Termična modifikacija lesa je vplivala tudi na striţno trdnost lepilnih spojev. Striţna trdnost FF lepilnih spojev je padala z naraščanjem temperature modifikacije lepljencev, kar je bila posledica manjše utrjenosti lepila in niţje trdnosti modificiranega lesa. Po namakanju v vodi se je striţna trdnost FF spojev prepolovila, vendar so bolj modificirani preskušanci obdrţali večji deleţ začetne trdnosti. Povprečna efektivna penetracija FF lepila je sicer nekoliko naraščala s stopnjo modifikacije, vendar razlike niso bile statistično značilne. Termična modifikacija je zmanjšala omočitev površine lesa z vodo, toda izboljšala omočitev površine lesa s FF lepilom. Pri spojih s PVAc lepilom sta striţna trdnost spojev in deleţ loma po lesu padala s stopnjo termične modifikacije tako pri suhih preskušancih kot po namakanju preskušancev v vodi. Trdnost suhih PU lepilnih spojev se je zniţala glede na stopnjo termične modifikacije lesa, vendar manj kot pri PVAc lepilu. Po namakanju preskušancev v vodi pa sta se trdnost PU spojev in deleţ loma po lesu povečevala s stopnjo modifikacije lesa. Razlog je bil verjetno v navzemu vode in nabrekanju lesa. Navzem vode med 24 urnim namakanjem lepljencev v vodi je padal s stopnjo termične modifikacije lesa. Pri MUF lepilu je striţna trdnost suhih spojev padala s stopnjo termične modifikacije nekoliko bolj kot pri PU lepilu, vendar precej manj kot pri PVAc lepilu. Po namakanju preskušancev je striţna trdnost MUF spojev padla na polovico začetne trdnosti suhih spojev ter bila neodvisna od stopnje termične modifikacije, vendar je deleţ loma po lesu ostal 100 %. Skupna ugotovitev pri vseh lepilih je bila, da višja kot je bila stopnja termične modifikacije, manjša je bila deformacija pri kateri je prišlo do loma ter bolj krhek je bil lom. Skupna delaminacija PVAc lepilnih spojev je bila precej velika in se je povečevala s stopnjo termične modifikacije lesa. Pri PU in MUF lepilnih spojih izrazite delaminacije ni bilo.In the thesis the effect of the temperature used for the thermal modification of wood on the curing of adhesive and on bond performance was investigated. Spruce wood, heat treated at temperatures of 150, 170, 190, 210 and 230 °C, and four different types of adhesives were used: one adhesive for hot pressing, phenol-formaldehyde (PF), and three adhesives for cold setting: polyvinyl acetate (PVAc), polyurethane (PU) and melamine-urea-formaldehyde (MUF). The curing of the adhesives was monitored by measuring their rheological properties with a rheometer. Wooden discs, prepared from wood that had been subjected to different degrees of thermal modification and having different moisture contents, were used, instead of standard aluminium discs. The oscillation test with the "multiwave" measurement technique was used. It was found that the PVAc, PU and MUF adhesives cured more slowly depending on the degree of thermal modification, but the reasons for the retardation of curing were different. PVAc and MUF curing was slower because of the lower degree of adsorption of water in the modified wood, whereas the PU cured slower because of the lower moisture content of the modified wood. Thermal modification had a significant influence on the shear strength of the adhesive bonds. The shear strength of the PF adhesive bonds decreased with an increasing temperature of thermal modification, because of the lower degree of adhesive cure and the lower strength of the modified wood. After soaking in water, the shear strength of the PF joints reduced by half, but the more strongly modified specimens retained a greater proportion of the initial shear strength. The average effective penetration of the PF adhesive slightly increased with the degree of thermal modification, but these differences were not statistically significant. Thermal modification reduced surface wetting with water, but improved wetting with the PF adhesive. The shear strength and wood failure of the PVAc adhesive bond (of dry specimens and after soaking in water) decreased with a higher degree of thermal modification. The shear strength of the PU adhesive bonds decreased with degree of thermal modification of the wood, but less than in the case of the PVAc adhesive bonds. After soaking in water the shear strength and wood failure of the PU adhesive bonds increased with the degree of thermal modification. The reason was probably water intake and swelling of the wood. The water intake after 24 h of soaking decreased with the degree of thermal modification of the wood. The shear strength of the MUF adhesive bonds decreased with the degree of thermal modification slightly more than that of the PU adhesive bonds, but much less than that of the PVAc adhesive bonds. After soaking in water the shear strength of the MUF adhesive bonds dropped to half the initial dry strength, and was observed to be independent of the degree of thermal modification. The average wood failure of the wood remained at 100 %. In the case of all the adhesives bonds is was noticeable that with a higher degree of thermal modification the deformation was smaller when failure of the bond occurred, and that the failure was more brittle. The total delamination of the PVAc adhesive bonds was quite high, and increased with the degree of thermal modification of the wood. Delamination of the PU and MUF adhesive bonds was not pronounced

Adhesive bonding of heat-treated wood

S termično modifikacijo lesu zmanjšamo ravnovesno vlažnost, izboljšamo dimenzijsko stabilnost, povečamo trajnost ter odpornost proti glivam in insektom. Termično modificiran les ima drugačne lastnosti kot naraven les, zato je lepljenje takega lesa običajno zahtevnejše. Študije so pokazale, da termično modificiran les lahko kakovostno lepimo z večino industrijskih lepil za les, vendar je pogosto potrebno prilagoditi pogoje lepljenja in/ali modificirati lastnosti lepila. Trdnost lepilnih spojev termično modificiranega lesa je v splošnem odvisna od vrste lesa in stopnje modifikacije ter vrste lepila. Težavno je predvsem lepljenje z lepili na vodni osnovi, saj je modificiran les bolj hidrofoben.Thermal modification of wood reduces its equilibrium moisture content, improves dimensional stability, and increases durability and decay resistance.Bonding of heat-treated wood is difficult, because of its modified properties. Several studies had shown that heat treated wood can be sufficiently bonded with most of industrial wood adhesives, but usually some modifications of bonding process and/or adhesive need to be made. Adhesive bond strength of heat-treated wood depends on wood species, degree of modification and type of adhesive. Especially bonding with waterborne adhesives presents difficulties, because heat-treated wood is more hydrophobic

Obdelava smrekovega lesa s plazmo spremeni njegove dielektrične lastnosti

The effects of dielectric barrier discharge (DBD) plasma treatment on the dielectric properties of Norway spruce wood (Picea abies (L.) Karst.) were investigated using dielectric analysis. Dielectric constant (i.e. permittivity) and loss coefficient were determined at various frequencies. The resulting changes on lamellae specimens of different thicknesses were compared with the change in mass and moisture content. A significant influence of the plasma was found, leading to an increase of the dielectric constant by about 2%, and a decrease of sample mass directly after the plasma treatment by approx. 14%, whereas a reduction in moisture content by only about 0.6% and a corresponding change in loss coefficient were detected. Overall, the mechanisms of the observed changes remain unclear and seem mainly uncorrelated with the hitherto known chemical changes in wood surfaces caused by similar plasma discharges.Vpliv obdelave z dielektrično barierno razelektritveno (DBD) plazmo na dielektrične lastnosti smrekovega lesa (Picea abies (L.) Karst.) smo raziskovali z dielektrično analizo. Pri različnih frekvencah smo določili dielektrično konstanto in faktor dielektričnih izgub. Nastale spremembe na vzorcih lamel različnih debelin smo primerjali s spremembo mase in vlažnosti. Ugotovljen je bil pomemben vpliv obdelave s plazmo, kar je povzročilo povečanje dielektrične konstante za približno 2 % in zmanjšano maso vzorca neposredno po plazemski obdelavi, medtem ko je bilo zaznano zmanjšanje vlažnosti za približno 0,6 % in ustrezno povečanje tangensa izgubnega kota. Na splošno mehanizmi opaženih sprememb ostajajo nejasni in se zdijo v glavnem nepovezani z do zdaj znanimi kemičnimi spremembami na površinah lesa, ki jih povzročajo podobne plazemske razelektritve

Spremljanje reoloških lastnosti lepil med utrjevanjem

Merjenje reoloških lastnosti se večinoma uporablja za spremljanje kakovosti izdelkov in njihovih lastnosti v proizvodnji hrane, kozmetike, gume, plastičnih mas, barv, črnil in mnogih drugih izdelkov. Spremljanje utrjevanja lepil z merjenjem sprememb reoloških lastnosti z reometrom je razmeroma nova tehnika, ki omogoča merjenje dinamičnega strižnega modula, spremembe viskoznosti in izgubnega kota med utrjevanjem proučevanega lepila. V osnovi je podobna klasični dinamični mehanski analizi (DMA), saj vzorec materiala med utrjevanjem dinamično obremenjujemo in merimo njegov odziv na obremenitev. Rezultati reoloških meritev omogočajo natančno določitev točke želiranja in zamreženja lepila. Z dodatno opremo lahko hkrati spremljamo tudi spremembe dielektričnih lastnosti lepila med utrjevanjem ter na ta način ugotovimo povezavo med njegovimi dielektričnimi in reološkimi lastnostmi, kar je izjemno pomembno za aplikacijo v industriji lepljenega lesa.Measuring the rheological properties is often used for quality control in food, cosmetics, tires, polymers, colors, and many other products. Monitoring adhesive cure by measuring change of rheological properties is a new technique. This method enables measuring of dynamic shear modulus, viscosity change, and phase angle during curing of selected adhesive. It is similar to dynamic mechanical analysis (DMA), because the sample of material is dynamically loaded during curing and it response is measured. Rheological measurements allow to determine gel point and vitrification point. With additional equipment is also possible to measure change of dielectric properties and find out the correlation between dielectric and rheological properties, what is very important for application in laminated wood industry

Design and Manufacturing of Organic Shape Furniture

Wooden furniture of organic shapes was mostly handmade in the past, each piece was almost unique, since the manufacturing processes did not allow repeatability and larger quantity production of the same products. Today, modern 3D modelling software leads to completely different prospective in wooden furniture design and production. It enables modelling of any kind of shape, based on ideas, natural shapes, even 3D scanned existing shapes, etc. Furthermore, prototypes can be 3D printed. This enables that visual presentation of designed form is made in real. Based on the printed forms virtual models can be improved leading to the final sophisticated model. Additionally, during design process the best construction details can be made to improve material efficiency and manufacturing time. Final product can be than made on CNC machines, enabling reproduction of the same product of desired shape in chosen quantities

Timber passive house technologies of Slovenian contemporary architecture

Energy efficiency is essential in the efforts to achieve a 20 % reduction of primary power consumption by 2020. It is widely recognized that the potential of energy saving in buildings is large. Considering the tendencies of energy production and price, it is becoming urgent to reduce energy consumption in buildings. The choice of materials for a building with a high energy efficiency becomes much more important and strategies for reducing the use of primary energy for the production of materials and components becomes key. Renewable building materials should already be integrated into the early phases of building planning. The positive trend towards wooden construction is dictated by international guidelines, where a wooden building is an important starting point, not only for low-energy, but also low-emission building with exceptional health and safety aspects. In Europe, the most comprehensive and widely used is a concept of ultra-low energy house, more precisely, the passive house concept. Most Slovenian buildings combine contemporary styling with a degree of energy efficiency that comes close to passive house standards. It is widely recognised that the Slovenian construction industry is relatively advanced in the field of low energy buildings. In the light of the growing importance of energy-efficient building methods, it could be said that timber passive house would play an increasingly important role in the future