The chemical, kinetic and mechanical characterization of tannin-based adhesives with different crosslinking systems
The chemical, kinetic and mechanical characterization of tannin-based adhesives with different crosslinking systems
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DOI：
10.1016/j.ijadhadh.2016.01.006
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发表时间：
2016-07-01
影响因子：
3.4
通讯作者：
Laborie, Marie-Pierre
中科院分区：
文献类型：
--
作者：
Boehm, Ricarda;Hauptmann, Markus;Laborie, Marie-Pierre
研究了单宁基树脂的网络形成、固化特性和键合性能，建立了B阶段和c阶段之间的结构-性能关系。合成了单宁醛和碱催化的自缩合单宁树脂，并通过GPC、DMA和C-13 CP/MAS NMR谱和溶剂稳定性测试对其分子量分布、固化动力学和固化化学进行了表征。通过剪切试验和粘接线的微观观察，进一步确定了树脂作为木材胶粘剂的性能。用高活性醛（如甲醛或乙二醛）制备的树脂具有明显的异缩合反应程度、快速的固化动力学、高的储存模量和良好的溶剂稳定性。相比之下，用大体积的低反应性醛（如柠檬醛）制备的树脂主要由自缩合反应组成，并且表现出较慢的固化动力学、较低的储存模量和c级树脂的溶剂稳定性，类似于那些整齐的自缩合单宁树脂。然而，所有的树脂系统都满足木材胶粘剂粘合的标准要求，用于室内应用。此外，在固化过程中，存储模量的增加被发现是木材粘合组件刚度的一个很好的预测指标，有助于区分自凝和异凝固化化学。(C) 2016 Elsevier Ltd.版权所有。
Network formation, cure characteristics and bonding performance of tannin-based resins were investigated in order to establish structure-property relationships between the stage B and stage C. Tannin-aldehyde and base-catalyzed autocondensed tannin resins were synthesized and characterized for molecular weight distribution, cure kinetics and cure chemistry by means of GPC, DMA and C-13 CP/MAS NMR spectroscopy and solvent stability tests. The resins performance as wood adhesives was further established from lap-shear tests and microscopic observation of the bondline. Resins prepared with highly reactive aldehydes, such as formaldehyde or glyoxal, exhibited a significant extent of hetero-condensation reactions, fast cure kinetics, a high storage modulus and good solvent stability of the stage C-resin. In contrast, resins prepared with bulky aldehydes of low reactivity, such as citral, were dominated by autocondensation reactions, and exhibited slower cure kinetics, a lower storage modulus and solvent-stability of the stage C-resin, alike those neat autocondensed tannin resins. However, all resin systems fulfilled the standard requirements for wood adhesive bonding for interior applications. Additionally, storage modulus increase during cure was found to be a good predictor of the stiffness of the wood-bonded assembly, useful to discriminate between the autocondensation and heterocondensation cure chemistries. (C) 2016 Elsevier Ltd. All rights reserved.