Cellulose ( IF 4.9 ) Pub Date : 2021-07-21 , DOI: 10.1007/s10570-021-04088-y Eko Setio Wibowo 1 , Byung-Dae Park 1
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When applying an adhesive to wood, the chemical heterogeneity of the wood cell walls makes it difficult to understand the contribution they make to the interfacial adhesion between the adhesive and the wood as the adhesion is a very complex physical and chemical phenomenon. This study, for the first time, directly measured the surface adhesion between cellulose, a major component of wood, and urea–formaldehyde (UF) resin adhesives. The adhesion between thin, smooth nanocellulose films, such as cellulose nanofibrils (CNFs), carboxymethylated nanofibrils (CM)–CNFs, and carboxylated cellulose nanocrystals (C–CNCs), and UF resins with two formaldehyde to urea (F/U) molar ratios of 1.0 and 1.6 was measured using two approaches: (1) direct measurement of the adhesion force between nanocellulose films and liquid droplets of the UF resins, and (2) calculation of the work of adhesion between films of the nanocelluloses and UF resins using the contact angle and the van Oss–Chaudhury–Good method. The results show that the total surface free energies, either between the different nanocelluloses or between the two UF resins are somewhat similar, indicating the similarity in their surface properties. However, the adhesion force and work of adhesion of 1.6 UF resins with different types of nanocellulose are higher than those of 1.0 UF resins, which shows that van der Waals forces are dominant in their molecular interactions. These results suggest that the adhesion between 1.6 UF resins and nanocellulose is stronger than that when 1.0 UF resins are used because the 1.6 UF resins have a more branched structure, smoother surface, and higher surface free energy.
Graphic abstract
中文翻译：
直接测量纳米纤维素薄膜与脲醛树脂粘合剂之间的表面粘附力
当将粘合剂应用于木材时，木材细胞壁的化学异质性使得难以理解它们对粘合剂和木材之间的界面粘合的贡献，因为粘合是一种非常复杂的物理和化学现象。该研究首次直接测量了纤维素（木材的主要成分）与脲醛 (UF) 树脂粘合剂之间的表面粘合力。薄而光滑的纳米纤维素薄膜，如纤维素纳米纤丝 (CNFs)、羧甲基化纳米纤丝 (CM)-CNFs 和羧化纤维素纳米晶 (C-CNCs) 与具有两种甲醛与尿素 (F/U) 摩尔比的 UF 树脂之间的粘附使用两种方法测量 1.0 和 1.6：(1) 直接测量纳米纤维素薄膜和 UF 树脂液滴之间的粘附力，(2) 使用接触角和 van Oss-Chaudhury-Good 方法计算纳米纤维素和 UF 树脂膜之间的粘附功。结果表明，不同纳米纤维素之间或两种超滤树脂之间的总表面自由能有些相似，表明它们的表面性质相似。然而，1.6 UF树脂与不同类型纳米纤维素的粘附力和粘附功均高于1.0 UF树脂，这表明范德华力在它们的分子相互作用中占主导地位。这些结果表明，1.6 UF 树脂与纳米纤维素之间的粘合力比使用 1.0 UF 树脂时更强，因为 1.6 UF 树脂具有更多支化的结构、更光滑的表面和更高的表面自由能。
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