基于没食子酸和漆酚的可逆交联聚氨酯的制备、固化与性能研究

Thermosetting polyurethane is widely used and its demand is very huge, but its stable crosslinking network makes it implastic and unrecoverable, which lead to resource waste and environment pollution. Inspired by the reversible reaction between phenol hydroxyl and isocyanate, this project is plan to prepare the self-healing and recyclable thermosetting polyurethane with covalent adaptable networks via replacing polyols by natural polyphenols gallic acid and urushiol to crosslink reversibly with polyisocyanates. Esterification, etherification, Mannich reaction and physical blending are applied in order to liquefy gallic acid derivatives and adjust the reactivity of the phenols. Solid nuclear magnetic resonance will be used to characterize the changes of the covalent bonds in the networks. thermoanalysis and rheology could be utilized to study the kinetics of the reversible reaction and the rheology properties of the thermosetting polyurethane, so that the remolding process conditions could be available. The microstructure of self-healing scar could be observed by the microscopic method, and the thermosetting properties of the remolding materials can be confirmed by static thermal analysis and swelling method. Finally we will test the thermal and mechanical properties of the materials before and after self-healing or recycled to discuss the effect of gallic acid/urushiol ratios and remolding process on the properties of recycled materials. This proposal present a new system that the thermosetting polyurethane networks can crosslink reversibly, it is a universal new technology. Compared with the existing research, its application prospect is more remarkable, meanwhile, it will promote the higher-value utilization of these forestry resources gallic acid and urushiol.

热固性聚氨酯应用广泛且需求量大，但稳定的交联结构让其不能回收再成型，造成资源浪费和环境污染。受酚羟基与异氰酸酯的可逆反应的启发，本研究利用天然多元酚没食子酸和漆酚替代多元醇，与多异氰酸酯进行可逆交联，实现聚氨酯中共价键的重组和材料的自修复与可回收。通过酯化、醚化、Mannich反应和物理共混的方式，液化没食子酸和调节酚羟基活性；用固体核磁表征交联网络中共价键的变化，并用热分析和流变方法研究可逆反应动力学和可逆交联的流变特性，获得再成型工艺条件；用显微手段评价疤痕的自修复程度，用静态热分析和溶胀性测试再生材料的热固性恢复程度。最后通过热、力学性能的测试，探讨没食子酸/漆酚配比、再生条件对聚氨酯性能的影响。本研究提出了一个聚氨酯可逆交联的新体系，是一种具有普遍意义的新方法。与现有研究相比，本体系具有更显著的应用前景，同时也有利于推动林特资源没食子酸和漆酚的高附加值利用。

热固性聚氨酯应用广泛且需求量大，但稳定的交联结构让其不能回收再成型，造成资源浪费和环境污染。受酚羟基与异氰酸根的可逆反应启发，本项目利用天然的多元酚代替多元醇与多异氰酸酯反应，利用酚型氨基甲酸酯可以在一定温度下断裂重组的特性，合成具有自修复功能的热固性聚氨酯。研究了没食子酸丙酯基、漆酚基及桐油基多元酚基自修复聚氨酯的合成及结构表征。采用变温傅里叶红外（Variable-FT-IR）、热稳定性分析（TGA）、动态热机械分析（DMA）、差示扫描量热法（DSC）以及拉伸测试等手段确定聚氨酯的最佳自修复温度和修复效率，研究了聚合和解聚反应的动力学；比较了不同结构的多元酚和聚氨酯预聚体为原料的自修复热固性聚氨酯的性能，探究了不同的酚类苯环结构上的取代基对合成的热固性聚氨酯自修复性能的影响以及软硬链段比例对自修复聚氨酯性能的影响。没食子酸丙酯基聚氨酯的修复温度为120℃，修复后其拉伸强度达到原始样条的70%，断裂伸长率达到原始样条的86%。在相同温度下，不同取代基多元酚聚氨酯的修复能力高低为：邻苯二酚基聚氨酯<漆酚基聚氨酯<没食子酸丙酯基聚氨酯。漆酚的引入在一定程度上降低没食子酸丙酯基聚氨酯的玻璃化转变温度、储能模量及机械性能；当-OH(没食子酸丙酯):-OH(漆酚)=1:1时，自修复效率最高。聚氨酯预聚体中异氰酸根含量增加，聚氨酯的初始热分解温度逐渐降低；拉伸强度、断裂伸长率、存储模量和玻璃化转变温度都有所提高；聚氨酯的自修复效率在50%以上。桐油基多元酚基聚氨酯修复后拉伸强度为原始样条的46-64%，断裂伸长率为原始样条的81-88%。本研究为热固性树脂的修复与回收研究提供了一种新的思路，有利于推动林产资源没食子酸、漆酚和桐油的高附加值利用。研究过程中发表论文7篇，申请专利3项，培养研究生2名。