Browsing by Author "Ayata, Umit"
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- Calorific Power Improvement of Wood by Heat Treatment and Its Relation to Chemical CompositionPublication . Domingos, Idalina; Ayata, Umit; Ferreira, José; Cruz-Lopes, Luísa; Sen, Ali; Sahin, Sirri; Esteves, BrunoChemical composition influences the calorific power of wood, mainly due to the calorific power of structural compounds and extractives. Heat treatment changes the chemical composition of treated wood. This work studies the relationship between chemical composition and calorific power improvement by heat treatment. Samples were heat-treated by the ThermoWood process ® for 1 h and 2 h. High heating value (HHV) and chemical composition; lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol, and water were determined. The HHV of untreated wood ranged between 18.54–19.92 MJ/kg and increased with heat treatment for all the tested species. A positive linear correlation was found between HHV and Klason lignin (R2 = 0.60). A negative trend was observed for holocellulose, cellulose, and hemicelluloses content against HHV, but with low determination coefficients for linear regression. The best adjust for polysaccharides was found for hemicelluloses content. A positive correlation could be found for dichloromethane extractives (R2 = 0.04). The same was obtained in relation to ethanol extractives with R2 = 0.20. For water and total extractives, no clear positive or negative trends could be achieved. The results showed that the HHV of wood increased with heat treatment and that this increase was mainly due to the increase in lignin content.
- Changes in the content and composition of the extractives in thermally modified tropical hardwoodsPublication . Esteves, Bruno; Ayata, Umit; Cruz-Lopes, Luísa; Brás, Isabel; Ferreira, José; Domingos, IdalinaChemical composition of wood is known to change during thermal treatments. Two species grown in Turkey, afrormosia (Pericopsis elata) and duka (Tapirira guianensis) were heat treated according to Thermowood® method. Lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol and water were determined. Wood extracts were analysed by gas chromatography with mass detection and existing compounds were identified by NIST17 database. Results show that hemicelluloses and cellulose content decreased for both heat-treated woods along the treatment while lignin percentage increased. The analysis of extractives has shown several compounds normally associated to lignin thermal degradation that increased along the treatment. At the same time several compounds associated to carbohydrate thermal degradation were found in all the extracts for both heat-treated woods. These founding have allowed the understanding of the degradation pattern of wood during thermal modification. There was not much difference between afrormosia and duka woods structural compounds behaviour along thermal modification. However, the variation of the amount of extractives along the treatment depended on the species.
- Determination of decay resistance against Pleurotus ostreatus and Coniophora puteana fungus of heat-treated scotch pine, oak and beech wood speciesPublication . Ayata, Umit; Akcay, Caglar; Esteves, BrunoThe objective of this study, to investigate decay resistance against Pleurotus ostreatus and Coniophora puteana fungus of heat - treated (ThermoWood method) Scotch pine, oak and beech wood species. Scotch pine ( Pinus sylvestris ), oak ( Quercus petreae ) and beech ( Fagus orientalis ) wood species were heat treated at 190°C for 2 h, 212°C for 1 h and 2 h by the ThermoWood® method. Untreated and heat - treated specimens were exposed to white - rot fungus ( Pleurotus ostreat us ) and brown - rot fungus ( Coniophora puteana ) for 12 weeks according to procedures defined in JIS K 1571 standard. After weight losses of all specimens were calculated. According to the results, least weight loss was determined on heat treated at 212°C for 2 h. Heat treatment can be used effectively against fungal attack for Scotch pine, oak and beech wood species.
- Determination of some wood properties and response to weathering of Citrus limon (L.) Burm woodPublication . Şahin, Sırrı; Ayata, Umit; Bal, Bekir Cihad; Esteves, Bruno; Can, Ahmet; Sivrikaya, HüseyinOrange is a fruit of the Citrus genus in the family Rutaceae. It is assumed to have originated in southern Asia, and to have been first cultivated in China around 2500 BC. There is little knowledge on the quality of wood from orange trees, which is occasionally used in fine woodwork, tool handles, mosaics, and marquetry. This work aimed to evaluate the possibility of using orange wood from agricultural conversions and orchard plantation renewals to make products with a high value. Logs from plantations located in southern Italy were collected, and the key aspects for determining the suitability of using the wood as flooring were examined. Laboratory tests were carried out to determine the shrinkage, dimensional stability, and surface hardness, which included an indentation test on the wood flooring. Drying trials were also performed, and prototypes of flooring were prepared so professionals and end users could evaluate the aesthetic value. The results confirmed that the wood from orange trees is fine-grained, and is characterized by a high density and shrinkage, average dimensional stability, and high surface hardness. The results of the tests suggested performing careful drying and following specific procedures according to the size of the elements. The wood was highly appreciated by the users, which confirmed the possibility of using this wood as a renewable raw material, despite the limited availability, for manufacturing high-quality products.
- Effect of Thermal Aging on Colour and Glossiness of U System Varnish-applied Laminated Parquet LayersPublication . Ayata, Umit; Sahin, Sirri; Esteves, Bruno; Gurleyen, LeventChanges are reported in perpendicular and parallel glossiness, lightness (L*), red colour (a*) tone, and yellow colour (b*) tone due to thermal aging in beech (Fagus orientalis Lipsky), maple (Acer pseudoplatanus L.), northern red oak (Quercus rubra L.), American black walnut (Juglans nigra L.), and walnut (Juglans regia L.) wood coated with a UV system commonly used on laminated parquets. Coated samples were exposed to different thermal aging levels (30 °C for 30 days, 60 °C for 60 days, and 90 °C for 90 days). Colour and gloss were determined before and after the thermal aging processes. The L* decreased for all species with the thermal aging decreasing more for more intense processes. Variations of the a* and b* colour parameters depended on the species. The colour parameters changed for temperatures higher than 30 °C. In general, glossiness decreased proportionally to the severity of the thermal aging for all of the species studied.
- Effects of thermal modification of oak wood upon selected properties of coating systemsPublication . Gurleyen, Levent; Ayata, Umit; Esteves, Bruno; Gurleyen, Tugba; Cakicier, NevzatHeat treatment processes are usually used in low valued softwoods however there has been an increased use to change the natural colour of more valuable hardwoods without chemicals to be use indoors mainly for parquet floors. In this study, wood samples from oak (Quercus petreae L.) wood were heat treated (ThermoWood method) at 190oC for 2 hours and 212oC for 1 to 2 hours. Untreated and heat treated wood surfaces were coated by two different processes with an UV varnishing system according to manufacturer recommendations. The objective of this study was to investigate some surface properties like adhesion, glossiness, pendulum hardness and color (L*, a*, b*, ΔE, ΔL*, Δa* and Δb*). With heat treatment Lightness decreases and its magnitude is higher for higher temperatures and treating times being lower for double coated wood. There was a slight increase followed by a decrease in redness (lower a*) and a clear decrease in the yellow tone (b*). Total color variation increased with the intensity of the treatment and glossiness decreased (more for single coated wood). The adhesion strength and surface hardness decreased with the heat treatment for both single and double coated wood.
- Land use impact of maritime pine and eucalypt: A life cycle assessment studyPublication . Ferreira, José; Esteves, Bruno; Ayata, Umit; Cruz-Lopes, Luísa; Domingos, IdalinaThe forestry sector in Portugal faces important challenges, resulting in an increased incidence of fires and the action of pathogens, which puts the sustainability of forest resources at risk. Due to the economic, social, and environmental importance of forests, this work assessed the land use environmental impact of maritime pine and eucalypt standing in Portuguese forests. SimaPro software was used to translate the inventory table results into land use impact category. The ILCD 2011 Midpoint+ method was chosen to assess the “land use” environmental impact that focuses on soil quality and its indicator (kg carbon deficit), which describes the changes in soil organic matter associated with land interventions. The results showed that for the first rotation time, the land use impact category per cubic meter of maritime pine is 18423 kg C deficit and 23430 kg C deficit for eucalypt, which means that the land use impact category of eucalypt is 27% higher than the impact of maritime pine.