Türel Tankut, Eling Berend, Cristadoro Anna M, Mathieu Thomas, Linnenbrink Martin, Tomović Željko
Polymer Performance Materials Group, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
Institute of Technical and Macromolecular Chemistry, University of Hamburg, Bundesstrasse 45, 20146 Hamburg, Germany.
ACS Appl Mater Interfaces. 2024 Feb 7;16(5):6414-6423. doi: 10.1021/acsami.3c17416. Epub 2024 Jan 28.
Moisture-curing one-component polyurethane systems in adhesive, sealant, and coating applications may show blister formation upon cure. Blisters can be formed when carbon dioxide, generated in the reaction with isocyanate and water, is trapped in the film. This problem can be mitigated by employing latent hardeners such as blocked polyamines, which are activated upon moisture exposure. The hydrolysis of the latent hardener yields the polyamine that quickly reacts with the isocyanate, forming urea linkages, and then chain extends the polymer. The hydrolysis also releases the blocking agent, which can potentially create an unpleasant odor. In this work, a series of di- and trifunctional aldimines were synthesized from commercially available polyamines, biobased hydroxymethyl furfural, and lauroyl chloride. Hydroxymethyl furfural was first esterified with lauroyl chloride and subsequently condensed with the polyamines to form the aldimines. The application of these novel aldimines in a model moisture-curing system allowed the preparation of blister- and odor-free castings. Based on our results, the mechanical performance of the different aldimines in casting and adhesive applications could be related to the polymer network density. This was dependent on the rate of the aldimine hydrolysis reaction to produce the polyamine. In particular, the use of aldimines prepared from polyether amines and 1,5-diamino-2-methylpentane showed excellent adhesive properties.
用于粘合剂、密封剂和涂料应用的湿气固化单组分聚氨酯体系在固化时可能会出现起泡现象。当与异氰酸酯和水反应生成的二氧化碳被困在漆膜中时，就会形成气泡。通过使用潜伏性固化剂（如封闭型多胺）可以缓解这个问题，封闭型多胺在接触湿气时会被激活。潜伏性固化剂的水解会产生多胺，多胺会迅速与异氰酸酯反应，形成脲键，然后使聚合物发生扩链反应。水解还会释放出封闭剂，这可能会产生难闻的气味。在这项工作中，由市售多胺、生物基羟甲基糠醛和月桂酰氯合成了一系列二官能和三官能醛亚胺。羟甲基糠醛首先与月桂酰氯酯化，随后与多胺缩合形成醛亚胺。这些新型醛亚胺在模型湿气固化体系中的应用使得制备出无气泡和无气味的铸件成为可能。根据我们的结果，不同醛亚胺在铸造和粘合剂应用中的机械性能可能与聚合物网络密度有关。这取决于醛亚胺水解反应生成多胺的速率。特别是，由聚醚胺和1,5-二氨基-2-甲基戊烷制备的醛亚胺表现出优异的粘合性能。
