Lignin is a low-cost and renewable bioresource with a huge annual production promising to prepare sustainable materials. However, the poor interfacial adhesion between many lignin-polymer pairs deteriorates the mechanical performance of the composites, which seriously limits the application of lignin in 3D printing via fused depositional modeling. This work examined lignin-polyamide 12 (PA 12) intermolecular interactions (e.g., hydrogen bonding) to address the interface challenge. To realize this goal, the phenolic hydroxyl content was increased for a kraft softwood lignin using a LiBr/HBr demethylation procedure, increasing phenoxy content by 61.7%. Increased hydrogen bonding interactions between modified lignin (Pine-Lig-OH) and PA 12 demonstrated a significantly improved molten dynamic modulus by rheological analysis. Regarding mechanical properties, by adding 20 wt% of Pine-Lig-OH, the tensile strength and Young's modulus reached 46.6 MPa and 1.62 GPa, 30.2% and 33.9% higher than PA 12, respectively. Further morphological analysis proved the interfacial interactions are enhanced by showing the difference in the phase gaps. The dynamic mechanical analysis (DMA) supported the conclusion that Pine-Lig-OH could interact with polymer chains, alternating segmental movements due to the strong interaction. This study presents a method to enhance lignin composite properties by promoting interactions with the polymer matrix through modified functional groups, guiding future lignin composite research.

中文翻译：

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3D打印木质素复合材料木质素结构与性能之间的结构-性能关系

木质素是一种低成本、可再生的生物资源，年产量巨大，有望制备可持续材料。然而，许多木质素-聚合物对之间的界面粘附力较差，导致复合材料的机械性能恶化，这严重限制了木质素在熔融沉积建模3D打印中的应用。这项工作研究了木质素-聚酰胺 12 (PA 12) 分子间相互作用（例如氢键）以解决界面挑战。为了实现这一目标，使用 LiBr/HBr 去甲基化程序提高了牛皮纸软木木质素的酚羟基含量，使苯氧基含量增加了 61.7%。通过流变分析，改性木质素 (Pine-Lig-OH​​) 和 PA 12 之间氢键相互作用的增强表明熔融动态模量显着提高。机械性能方面，添加20 wt%的Pine-Lig-OH​​后，拉伸强度和杨氏模量达到46.6 MPa和1.62 GPa，分别比PA 12高30.2%和33.9%。进一步的形态分析证明，通过显示相隙的差异增强了界面相互作用。动态力学分析 (DMA) 支持以下结论：Pine-Lig-OH​​ 可以与聚合物链相互作用，由于强相互作用而交替链段运动。本研究提出了一种通过改性官能团促进与聚合物基体相互作用来增强木质素复合材料性能的方法，指导未来的木质素复合材料研究。