To meet the demands of the evolving circular economy, there is a growing need for renewable resources as base materials for innovative, easily recyclable products. Lignin, the second most abundant biopolymer, has emerged as a promising source of aromatics and reinforcing agent in polymer composites. For the successful manufacturing of homogeneous composite materials, good bonding between the coexisting phases is essential to prevent the formation of voids and agglomerates. Therefore, understanding the surface properties of these materials is crucial for designing optimal composite compounds. In this study, the wettability of lignin-cellulose composites and lignin samples obtained through supercritical water hydrolysis (SCWH) of birch wood is investigated. The contact angle (CA) technique, specifically the sessile drop method, was employed to assess and compare the wettability of SCWH lignin with commercially available lignin and raw birch wood. The results provide insights into their surface energy, adhesion, and hydrophilic or hydrophobic characteristics under processing conditions. All samples exhibited hydrophilicity, with an initial CA approximately 40 °, except for raw birch wood, which had a higher initial CA of ∼ 64°. Notably, when lignin is accompanied by significant amounts of cellulose, different trends in CA changes over time were observed. The influence of pressure on the CA between water and these polymers was also analyzed, but no significant impact was detected. This research advances the development of lignin-based materials with tailored surface properties for various industrial applications.

中文翻译：

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木材超临界水解对木质素材料的表面润湿性


为了满足不断发展的循环经济的需求，对可再生资源的需求日益增长，作为创新、易于回收产品的基础材料。木质素是第二丰富的生物聚合物，已成为聚合物复合材料中芳烃和增强剂的有前途的来源。为了成功制造均质复合材料，共存相之间的良好结合对于防止空隙和团聚物的形成至关重要。因此，了解这些材料的表面特性对于设计最佳复合化合物至关重要。本研究研究了木质素-纤维素复合材料和通过桦木超临界水解 （SCWH） 获得的木质素样品的润湿性。采用接触角 （CA） 技术，特别是无柄滴法，来评估和比较 SCWH 木质素与市售木质素和生桦木的润湿性。结果有助于了解它们在加工条件下的表面能、粘附力以及亲水或疏水特性。所有样品均表现出亲水性，初始 CA 约为 40°，但未加工的桦木具有较高的初始 CA 约为 64°。值得注意的是，当木质素伴有大量纤维素时，观察到 CA 随时间变化的不同趋势。还分析了压力对水和这些聚合物之间 CA 的影响，但没有检测到显着影响。这项研究推动了木质素基材料的开发，这些材料具有针对各种工业应用的定制表面特性。