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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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    Effect of Adhesion and Corrosion Performance of Geomet Basecoat (321)-Topcoat (ML Black) Applications on Cataphoretic Coating
    (Sakarya University, 2024) Usta, İbrahim; Yılmaz, Oguz; Gül, Minel; Can, Ahmet; Gül, Harun
    This study aimed to improve corrosion resistance and adhesion of metallic materials typically used in automotive application. A combination of cataphoretic and Geomet coatings has been used to improve corrosion resistance. Firstly, cataphoretic coating was applied and then the coating process was completed with Geomet 321 and ML Black respectively. The results of the corrosion tests were classified into different categories such as adhesion, water resistance, moisture resistance, salt resistance and cyclic tests. The corrosion properties of the two-and three-layer coatings were found to improve as a function of both the sandblast pre-treatment and the post-cataphoresis curing temperature. The findings show that the adhesion strength and corrosion properties of Geomet 321 increases with curing temperature and sandblasting. This study will be a contribution to the future of protective coatings in the automotive industry by describing the process steps necessary to achieve optimum results. © 2024, Sakarya University. All rights reserved.
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    Ekstraktiflerin dut odununun dış ortam dayanımına etkisi
    (2023) Ermeydan, Mahmut Ali; Dizman, Rıza; Tomak, Eylem Dizman; Can, Ahmet
    Bu çalışmada amaç, dut ağacı (Morus spp.) odun ekstraktiflerinin toprak üstü kullanım yerlerinde maruz kalabileceği UV ışığı başta olmak üzere dış ortamın bozundurucu faktörlerine karşı dayanıklılığının belirlenmesidir. Bu amaçla dut odun örnekleri öncelikli olarak sikloheksan/etanol (2/1) ardından aseton/su (7/3) ve son olarak da su ile toplam 21 gün boyunca üç aşamalı ekstraksiyona maruz bırakılmıştır. Ekstrakte edilen ve edilmeyen örnekler, denize yakın ve denize uzak 2 farklı alanda 6 ay süresince doğal dış ortam koşullarına bırakılmıştır. Örneklerin teste başladıktan 1, 3 ve 6 ay sonra rutubet miktarı, renk ve yüzey pürüzlülük ölçümleri, yüzey kimyası (ATR-FTIR) ve makroskopik açıdan değerlendirilmesi yapılmıştır. Sonuçlarda ekstraksiyon işlemi örneklerin başlangıç yüzey pürüzlülüğünü yaklaşık %50 oranında arttırmış ve rengini %4 oranında açılmasına neden olmuştur. Örneklerin yaşlandırma test süresi uzadıkça rutubet miktarının arttığı, ekstrakte edilen örneklerin ekstrakte edilmeyen örneklere, denize yakın alanda bekletilen örneklerin denizden uzaktaki alanda bekletilen örneklere kıyasla daha fazla rutubet miktarına sahip olduğu bulunmuştur. Ekstrakte edilmeyen örneklerde, yaşlandırma test süresince meydana gelen yüzey pürüzlülüğü, ekstrakte edilen örneklere kıyasla daha fazla olmuştur. Denizden uzak alanda bekletilen ekstrakte edilmeyen örneklerin pürüzlülüğü, denize yakın alanda bekletilen örneklere kıyasla daha fazla bulunmuştur. Yaşlandırılan örneklerde, test süresinin ilk 3 ayında ?L* değerlerinde artma, daha sonra azalma, buna karşın ?a* ve ?b* değerlerinde ise azalma eğilimi gözlenmiştir. 1. ay ile 6. ay arasında toplam renk değişimindeki (?E*) değişim ekstrakte edilmeyen örneklerde ekstrakte edilen örneklere kıyasla daha az bulunmuştur. Yüzey kimyası analizleri, örneklerdeki renk değişimini desteklemekle birlikte örneklerin lignininde yaşlanmanın ilk aşamasından itibaren bozunmalar olduğunu göstermiştir.
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    Modifiye edilmiş ahşabın hızlandırılmış yaşlandırması: Isıl işlemli örnekler ile asetillendirilmiş örneklerin kıyaslanması
    (2023) Tomak, Eylem Dizman; Can, Ahmet; Ermeydan, Mahmut Ali; Aydın, Mehmet Ali
    Bu çalışmada amaç, ısıl işlemli örnekler ile asetillendirilmiş örneklerin toprak üstü kullanım yerlerinde maruz kalabileceği UV ışığı başta olmak üzere dış ortamın bozundurucu faktörlerine karşı dayanıklılığının hızlandırılmış yaşlandırma testi ile belirlenmesidir. Bu amaçla ısıl işlemli çam ve dişbudak örnekleri ile asetillendirilmiş çam odunu örnekleri toplam 400 saat boyunca değişik döngülerde UV ışığı ve suya maruz bırakılmıştır. Örneklerin teste başladıktan 100, 200 ve 400 saat sonra renk ve yüzey kimyası (ATR-FTIR) analizi ile makroskopik açıdan değerlendirilmesi yapılmıştır. Sonuçlarda, ısıl işlemli örneklerin yaşlandırma test süresi uzadıkça koyu olan başlangıç renklerinin açılmaya başladığı ve toplam renk değişimi (?E*) değerlerinin giderek arttığı bulunmuştur. Buna karşın asetillendirilmiş örneklerde ilk 100 saat sonrasındaki renk değişimi test süresince dikkate değer ölçüde değişmemiş ve test boyunca neredeyse stabil olmuştur. Asetillendirilmiş örneklerin rengi hafif açılma eğilimindedir. Kontrol çam ve dişbudak örneklerinde toplam renk değişimi test süresince hafif bir artış eğiliminde olup, en büyük değişim ilk 100 saatlik test süresinde gerçekleşmiştir. Bu örneklerin rengi test süresince koyulaşma eğilimindedir. 100 saat sonrasında kontrol çam ve ısıl işlemli dişbudak örneklerinde çatlaklar gözlenmiş ve test süresince bu çatlaklar giderek artmış ve derinlemiştir. Yüzey kimyası analizleri, örneklerdeki renk değişimini desteklemekle birlikte örneklerin lignininde yaşlanmanın ilk aşasından itibaren bozunmalar olduğunu göstermiştir. Hızlandırılmış yaşlandırma testinin bozundurucu faktörlerine karşı, asetillendirilmiş örnekler ısıl işlemli örneklerden, ısıl işlemli örnekler ise kontrol örneklerinden daha iyi bir performans sergilemiştir.
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    Role of extractives on the weathering of tropical and temperate wood species in two above-ground fields: coastal or terrestrial
    (Taylor & Francis Inc, 2024) Ermeydan, Mahmut A.; Dizman, Riza; Tomak, Eylem D.; Can, Ahmet
    The effect of heartwood extractives on natural weathering of 5 temperate (juniper, walnut, oak, pseudoacacia, and chestnut) and 9 tropical (wenge, teak, iroko, dahoma, moabi, okan, padauk, ipe, and tatajuba) wood species against abiotic degrading agents at two sites was investigated. Wood species were exposed to three-stage extraction, then extracted and un-extracted samples were exposed outdoors for 12 months in two above-ground test sites, coastal or terrestrial. Samples were evaluated regarding moisture content, color change, surface roughness, and surface chemistry (ATR-FTIR) at 1, 3, 6, and 12 months of exposure. Results indicate that roughness and color change increased as the exposure time increased. Among the temperate species, the least rough surfaces were found in juniper, while iroko, ipe, and wenge were for tropical species. The location did not statistically affect roughness. Temperate species generally showed rougher surfaces than tropical species. The remarkable color change occurred in the first 3 months in temperate wood species and between 3 and 6 months in extractive-rich tropical wood species. The highest color change was seen in samples extracted and exposed on the terrestrial test site, while the lowest was in un-extracted samples exposed on the coast. Padauk had the most color change, while moabi had the least. The surfaces of temperate species showed darkening while the surfaces of tropical species showed lightening during the weathering exposure. FTIR studies confirmed that the change in the surface chemistry of temperate species mostly occurs in the first month, while surface degradation of some tropical species can take up to 3 months.
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    The effect of weathering aging on the color and roughness values of wood material impregnated with phase change materials with increased UV resistance
    (Bursa Technical University, 2023) Can, Ahmet
    This study aimed to increase the resistance of hybrid poplar (Populus x euroamericana) wood to UV rays that it may be exposed to in above-ground areas. For this reason, poplar wood samples were impregnated using lauric acid (C12H24O2), myristic acid (C14H28O2), and shellac polymer. The samples obtained were subjected to 400 hours of accelerated aging. The total color change (?E) of the samples was evaluated at 100, 200, and 400 hours after starting the test. In these examples, there was an increase in ?L* values of the variations without shellac (control, MA1, MA2, LA1, LA2) in the first 100 hours of the test period and a decrease in later times (200-400 hours). In contrast, the ?a* and ?b* values in the first 100 hours while there was a negative trend, an increase was observed in the positive direction at 200 and 400 hours. While an increased total color change (?E*) occurred in the early stages of the accelerated aging test, the color change decreased later. At the end of the 400 hours accelerated aging test, a total color change of 13.65 in the control samples and 14.54 in the shellac polymer was obtained. In contrast a lower total color change was obtained in the other variations. The minimum total color change of 2.95 was obtained in the MA2Sh group.
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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.