Department of Chemistry, CQC, University of Coimbra, Rua Larga, 3004-535 Coimbra, Portugal.
Science351-Disruptive & Sustainable R&D Innovations, Instituto Pedro Nunes, Ed. C, 3030-199 Coimbra, Portugal.
Molecules. 2022 Apr 29;27(9):2825. doi: 10.3390/molecules27092825.
Resole resins have many applications, especially for foam production. However, the use of phenol, a key ingredient in resoles, has serious environmental and economic disadvantages. In this work, lignin extracted from pine wood using a "green" solvent, levulinic acid, was used to partially replace the non-sustainable phenol. The physicochemical properties of this novel resin were compared with resins composed of different types of commercial lignins. All resins were optimized to keep their free formaldehyde content below 1 wt%, by carefully adjusting the pH of the mixture. Substitution of phenol with lignin generally increases the viscosity of the resins, which is further increased with the lignin mass fraction. The addition of lignin decreases the kinetics of gelification of the resin. The type and amount of lignin also affect the thermal stability of the resins. It was possible to obtain resins with higher thermal stability than the standard phenol-formaldehyde resins without lignin. This work provides new insights regarding the development of lignin-based resoles as a very promising sustainable alternative to petrol-based resins.
可再生树脂有许多应用，尤其是在泡沫生产方面。然而，作为可再生树脂关键成分的苯酚，其在环境和经济方面存在严重的弊端。在这项工作中，使用“绿色”溶剂——乙酰丙酸，从松木中提取的木质素被部分用来替代不可持续的苯酚。这种新型树脂的物理化学性质与由不同类型的商业木质素组成的树脂进行了比较。所有树脂都通过仔细调节混合物的 pH 值，将游离甲醛含量优化至 1wt%以下。木质素替代苯酚通常会增加树脂的粘度，而随着木质素质量分数的增加，粘度进一步增加。木质素的添加会降低树脂的凝胶化动力学。木质素的类型和用量也会影响树脂的热稳定性。与没有木质素的标准苯酚-甲醛树脂相比，有可能获得具有更高热稳定性的树脂。这项工作为开发基于木质素的可再生树脂提供了新的见解，它们是一种极具前景的可持续替代石油基树脂的选择。
