Wood products are extensively used to make furniture items and construction materials; however, the majority contain formaldehyde-based adhesives that raise serious health concerns. Here, we report a formaldehyde-free adhesive formulation comprised of two high-volume biorefinery biproducts, namely Kraft lignin (pulp and paper) and glycerol (biodiesel), and its adhesion properties as determined by ultimate shear stress as well as wood failure rates. We show that this lignin-based resin displays the same desirable characteristics as formaldehyde-based resins including water-tolerance, fast curing, and comparable adhesion performance. Chemical analysis indicates that resin curing occurs uncatalyzed via formation of ether bonds between lignin hydroxyl groups and the glycerol-derived crosslinker epoxide. We also show that different lignin and crosslinker feedstocks can be used in the formulation, in some cases with water as a cosolvent, to generate a set of lignin-derived resins with similar properties and mechanical strength. In contrast to the majority of formaldehyde-free adhesives, this lignin-epoxy formulation does not require the use of caustic base and known carcinogens. Furthermore, we demonstrate through mechanical testing and attention to processing conditions that this lignin-based resin has the potential to be a viable alternative to widely used formaldehyde resins.

中文翻译：

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源自生物质的木质素环氧树脂，可替代甲醛基木材胶粘剂

木制品被广泛用于制造家具和建筑材料。但是，大多数含有甲醛基胶粘剂，这会引起严重的健康问题。在这里，我们报告了一种无甲醛的粘合剂配方，该配方由两种高产量的生物精炼双产品，即卡夫木质素（纸浆和纸张）和甘油（生物柴油）组成，其粘合性能由最终剪切应力以及木材失效率确定。我们表明，这种木质素基树脂显示出与甲醛基树脂相同的理想特性，包括耐水性，快速固化和可比的粘合性能。化学分析表明，树脂固化是通过以下方式催化的：在木质素羟基和甘油衍生的交联剂环氧化物之间形成醚键。我们还表明，可以在配方中使用不同的木质素和交联剂原料，在某些情况下以水为助溶剂，以生成一组具有相似性能和机械强度的木质素衍生树脂。与大多数无甲醛粘合剂相反，这种木质素-环氧配方不需要使用苛性碱和已知的致癌物。此外，我们通过机械测试和对加工条件的关注证明，这种木质素基树脂有可能成为广泛使用的甲醛树脂的可行替代品。