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    Calorific Power Improvement of Wood by Heat Treatment and Its Relation to Chemical Composition
    (Mdpi, 2020) Domingos, Idalina; Ayata, Umit; Ferreira, Jose; Cruz-Lopes, Luisa; Sen, Ali; Sahin, Sirri; Esteves, Bruno
    Chemical 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 (R-2 = 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 (R-2 = 0.04). The same was obtained in relation to ethanol extractives with R-2 = 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.
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    Determination of Some Wood Properties and Response to Weathering of Citrus limon (L.) Burm Wood
    (North Carolina State Univ Dept Wood & Paper Sci, 2020) Sahin, Sirri; Ayata, Umit; Bal, Bekir Cihad; Esteves, Bruno; Can, Ahmet; Sivrikaya, Hiiseyin
    The ability of Citrus limon (L.) Burm wood to be used for flooring applications was considered in this work. Selected wood properties were determined, and the response to weathering was tested. Janka hardness, density, screw withdrawal resistance, color, glossiness, and artificial weathering (144, 288, and 432 h) were determined. The wood from Citrus limon was shown to be a dense wood with air density around 830 kg/m(3) and with a high Janka hardness of 138.0 N/mm(2), 120.4 N/mm(2), and 115.9 N/mm(2) for cross, tangential, and radial sections, respectively. This opens good perspectives to this kind of wood being used for flooring. Statistical analysis showed that both Janka hardness and screw withdrawal resistance were significantly different between surfaces. Nevertheless, the homogeneity groups showed that the main differences were between the surfaces in the longitudinal direction when compared with the transverse direction. The wood is lighter than most common woods and it is mainly yellow. After weathering, the wood became darker, redder, and yellower. Glossiness decreased in the first hours of the weathering period.
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    Effect of Heat Treatment on Shore-D Hardness of Some Wood Species
    (North Carolina State Univ Dept Wood & Paper Sci, 2021) Esteves, Bruno; Sahin, Sirri; Ayata, Umit; Domingos, Idalina; Ferreira, Jose; Gurleyen, Levent
    Hardness is an important wood property for several applications. Typically, it is necessary to use traditional methods, such as a universal test machine, to determine a wood's hardness value. This work reports the hardness of some wood species before and after heat treatment (ThermoWood method) using the Shore-D hardness method. The Shore-D hardness value of untreated wood ranged between 35.3 for Limba wood and 77.2 for Santos wood. With heat treatment, hardness decreased, and the decrease was greater for samples that underwent harsher treatment (2 h at 212 degrees C). The decrease of hardness was highest for Sipo wood (14%) and the lowest for Afrormosia wood (2.5%). Analysis of variance tests showed that there was a significant difference between wood species, heat treatment, and the interaction between both variables at the chosen level of significance (P <= 0.05). Results showed that Shore-D hardness could be used to measure hardness directly in a production line or in small wood companies without using a universal test machine.
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    EFFECTS OF ARTIFICIAL WEATHERING ON THE SURFACE PROPERTIES OF COATED RADIATA PINE
    (Univ Bio-Bio, 2023) Sahin, Sirri; Esteves, Bruno; Can, Ahmet; Sivrikaya, Huseyin; Domingos, Idalina; Ferreira, Jose; Ayata, Umit
    Radiata pine boards were coated with two different methods A and B both beginning with a hydro primer and finishing with a mat oil but method A using an acrylic high gloss coating and method B three layers of an acrylic sealer in between. The samples were subjected to aging processes for 144 h, 288 h, and 432 h by using UV-A 340 nm lamps. The CIE L*a*b* and CIE L*C*H* coordinates were determined (L*, a*, b*, C*, h(o)*, Delta E*), gloss (perpendicular (perpendicular to) and parallel (//) to the grain at 20 degrees, 60 degrees, and 85 degrees angles) and surface adhesion strength via the pull-off method were tested before and after weathering. Results have shown that lightness (L*), decreases with weathering for both varnish applications with a higher decrease for the B coating system. Redness increased for both applications with no significant differences. At the same time there was a yellowing of the samples along the weathering period. Parallel and perpendicular gloss decreased for 20 degrees and 60 degrees angles while it increased for 85 degrees angle. The adhesion strength of method A was higher and its decrease with weathering was smaller than for method B. Both varnish applications have proven to confer some protection against wood discoloration, but method A showed the best results and is therefore the best method to be used by radiata pine.