Accelerated weathering of modified wood: Comparison of heat treated samples with acetylated samples

Abstract

The aim of this study is to determine the accelerated weathering resistance of heat-treated samples and acetylated samples to the weathering factors of the outdoors, especially UV light. For this purpose, heat-treated pine and ash samples and acetylated pine wood samples were exposed to UV light and water at different cycles for a total of 400 hours. Color measurements, surface chemistry (ATR-FTIR), and macroscopic evaluation of the samples were performed after 100, 200, and 400 hours of the test period. In the results, it was found that as the weathering test period of the heat-treated samples increased, the dark initial color began to lighten, and the total color change (∆E*) values gradually increased. In the case of acetylated wood, the color change after the first 100 hours did not change remarkably during the test and was almost stable throughout the test. Acetylated samples tend to lighten slightly. Total color change in control pine and ash samples tended to increase slightly during the test, with the greatest change occurring during the first 100 hours of the test period. The color of these samples tends to darken during testing. After 100 hours, cracks were observed in the control pine and heat-treated ash samples, and these cracks gradually increased and deepened throughout the test. Surface chemistry analyses supported the color change in the samples, and showed that the lignin of the samples degraded from the first stage of weathering period. Acetylated samples performed better than heat-treated samples, and heat-treated samples performed better than control samples against the degrading factors of the accelerated weathering test.

Keywords

• Heat-treatment
• acetylated wood
• accelerated weathering
• color change
• surface chemistry

Modifiye edilmiş ahşabın hızlandırılmış yaşlandırması: Isıl işlemli örnekler ile asetillendirilmiş örneklerin kıyaslanması

Öz

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.

Anahtar Kelimeler

• Isıl işlem
• asetillendirilmiş odun
• yaşlandırma testi
• renk değişimi
• yüzey kimyası

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