Kısmen Pirolize Edilmiş ve Delignifiye Edilmiş Lignin ile Modifiye Edilmiş Üre-Formaldehit Reçine Sistemleri: Bir İnceleme

Öz

Üre-formaldehit (UF) reçineleri, odun kökenli ürünlerin üretiminde yaygın olarak kullanılan tipik yapıştırıcılardır. Bununla birlikte, formaldehit emisyonu yayan bu tür fosil yakıt bazlı reçinelerin kullanımı, çevre ve insan sağlığı açısından ciddi riskler oluşturmaktadır. Doğal yapıştırıcı ve su itici özelliklere sahip biyo-bazlı lignin polimeri, UF reçinelerinde ikame katkı maddesi olarak değerlendirilebilmektedir. Lignin reçine yapısına eklendiğinde, metilen bağlarının bulunduğu bölgelerde yeni bağların oluşmasıyla C-N bağlarının sayısında azalma meydana gelmektedir. Ancak, zayıf bağlanma kapasitesi ve amorf yapısı nedeniyle ham lignin doğrudan UF reçinelerine eklenememekte; ön işlemden geçirilmesi gerekmektedir. Bu doğrultuda, çalışmada inert atmosfer altında düşük sıcaklık bölgesinde ligninin kısmi pirolizi önerilmektedir. Söz konusu reaksiyon, kısmi C–O bağlarının parçalanması yoluyla daha uzun zincirli bir yapı oluşturarak ligninin kimyasal yapısını değiştirmektedir. Bu yöntemin formaldehit emisyonlarını azaltması beklenmekle birlikte, ortaya çıkan zincir yapısının su iticiliği artıracağı ve ligninin nem içeriğini düşüreceği öngörülmektedir. Literatürde yer alan araştırmalar, lignin katkılarının reçine viskozitesi, serbest formaldehit içeriği, yapışma performansı ve panel özellikleri üzerinde kayda değer etkiler gösterdiğini ortaya koymaktadır.

Anahtar Kelimeler

• Lignin
• UF Reçine
• Tutkal
• Kısmi Piroliz
• Depolimerizasyon

Urea-Formaldehyde Resin Systems Modified with Partially Pyrolyzed and Delignified Lignin: A Review

Abstract

Urea-formaldehyde UF resins are typical adhesives employed in the production of wood-derived products. Application of such fossil fuel-based resins that emit formaldehyde emissions endangers the environmental and human health conditions profoundly. Bio-based lignin polymer can be utilized as a replacement additive in UF resins because it has inherent adhesive and water repellent nature. When lignin is added into the structure of the resin, the C-N bonds are reduced through the creation of new bonds within regions containing methylene bonds. Raw lignin cannot be directly added to UF resins; it must undergo pretreatment due to its poor binding capacity and amorphous nature. Therefore, partial pyrolysis of lignin in the low temperature zone under inert atmosphere was suggested in this study. This reaction creates a longer chain structure by partial C-O bond fragmentation; thus lignin is altered. This method is likely to reduce the formaldehyde emissions, but the same chain structure will increase the water repellency and reduce the moisture content of lignin. Literature research reveals that lignin additives have great effects on resin viscosity, free formaldehyde content, adhesion quality and panel performance.

Keywords

• lignin
• UF Resin
• Depolimerization
• Partial Pyrolysis
• Adhesives

Kaynakça

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