Yazar "Aydin, Mehmet A." seçeneğine göre listele

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    A comparative study on photodegradation of twenty-three wood species after UV irradiation
    (Pergamon-Elsevier Science Ltd, 2024) Tomak, Eylem D.; Ermeydan, Mahmut A.; Can, Ahmet; Aydin, Mehmet A.
    The study investigates the effect of UV irradiation on different native and exotic wood species which is an open subject of research. Thirteen native wood species and ten exotic wood species, totally twenty-three wood species, all important for wood industry in Turkey, were subjected to UVA-340nm irradiation with a constant irradiance of 0.89 W/m2/nm and a temperature of 60 degrees C for 2, 4, 8, 16, 24, 48, 72, 96, 120, 144, 168, 252 and 336 h to determine the critical degradation time for the wood species. A short exposure time (from 2h to 48h) was especially studied since the previous studies reported that important and rapid changes occurred within the initial exposure periods. The effect of UV irradiation on wood surfaces was investigated by color, surface roughness, and FTIR-ATR measurements. The results proved that UV radiation caused a rapid color change for extractive-rich wood species at the initial period of exposure (16h-48h) which decreases upon prolonged exposure. The overall color change and surface roughness were higher for native wood species in a long exposure period than for exotic ones. Elm, oak, plane, walnut, acacia and linden as native wood species, iroko, tiama, acajou, okoume, garapa, sapelli, dibetou and teak as exotic wood species were found to be more resistant to color changes in prolonged irradiation periods, probably due to content of their components especially extractives and lignin. Similar to greater color change found within the beginning of the irradiation period (16h-48h), the first 8h-24h seemed to cause a greater increase in roughness for exotic species and 16h-24h for native wood species probably due to the changes in surface chemistry. Acacia, elm, cherry, beech, tiama, teak and okoume had the highest RI whilst S. pine, ash, poplar, plane, sapelli, limba and iroko had the lowest RI among the wood species. FTIR-ATR analysis demonstrated that UV light ended up with photodegradation of lignin and photooxidation of hemicelluloses which leads carbonyl-containing chromophores, even after short-time exposures (8h-24h).
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    Weathering of wood under indoor and outdoor environmental conditions
    (Wiley, 2025) Aydin, Mehmet A.; Can, Ahmet; Tomak, Eylem D.; Ermeydan, Mahmut A.
    This paper investigates the surface properties of 27 wood species exposed to indoor and outdoor weathering agents using above-ground test equipment for 1 year in Bursa, Turkey. For this purpose, colour changes, surface roughness and chemical composition of wood surfaces were analysed at an interval of 3 months during the exposure period. The results showed that the colour change on the wood surfaces exposed to outdoor weathering was observed during the first 3 months, and that the temperate wood species showed much more surface darkening and colour change compared with tropical wood species. In outdoor weathering, the least colour change was found in wenge as a tropical wood, and in walnut and elm as the temperate species, while the greatest colour change was in ayous and poplar. In the case of indoor weathering, iroko and cherry displayed the least amount of colour change, while the most was seen in wenge and Scots pine. Additionally, surface roughness and cracks increased with weather conditions, especially in outdoor conditions. Fourier Transform-infrared spectra revealed chemical changes, especially in carbonyl and lignin groups. Significant darkening, mould growth and crack formation on the surfaces were observed after the ninth month of outdoor weathering. However, cracks or mould formations were not observed on the samples exposed to indoor weathering; only a slight colour change was common. The study showed that the indoor and outdoor degradation agents, wood species and humidity conditions had an important role in the tested parameters.