Gomez-Lopez Alvaro, Ayensa Naroa, Grignard Bruno, Irusta Lourdes, Calvo Iñigo, Müller Alejandro J, Detrembleur Christophe, Sardon Haritz
POLYMAT and Department of Polymers and Advanced Materials: Physics, Chemistry and Technology, Faculty of Chemistry, University of the Basque Country UPV/EHU, Paseo Manuel de Lardizabal 3, 20018 Donostia-San Sebastián, Spain.
Center for Education and Research on Macromolecules (CERM), CESAM Research Unit, University of Liège, allée du 6 août, Building B6A, Agora Square, 4000 Liège, Belgium.
ACS Polym Au. 2022 Jun 8;2(3):194-207. doi: 10.1021/acspolymersau.1c00053. Epub 2022 Jan 10.
Poly(hydroxy urethane)s (PHUs) based on 5-membered cyclic carbonates have emerged as sustainable alternatives to conventional isocyanate-based polyurethanes. However, while from the point of view of sustainability they represent an improvement, their properties are still not competitive with conventional polyurethanes. In this work, the potential of PHUs as reversible hot-melt adhesives is discussed. We found that with a judicious choice of reagents (i.e., the dicyclic carbonate and diamine), the detrimental hydrogen bonding between the soft segment of the chains and the pendant hydroxyl groups was partially avoided, thus imparting PHUs with hot-melt adhesion properties (i.e., adhesion at elevated temperatures and cohesiveness at a temperature lower than / ). The importance of a balanced hard to soft segment ratio, along with the relevance of the chain extender in the final properties, is highlighted. Addition of aliphatic diamines (HMDA, 1,12-DAD) resulted in rubbery materials, while the employment of cycloaliphatic (CBMA) or aromatic ones (MXDA, PXDA) led to materials with hot-melt adhesive properties. The thermoreversibility of all compositions was assessed by rebonding specimens after lap-shear tests. Lap-shear strength values that were comparable to the virgin adhesives were observed. The breaking and reformation of hydrogen bonding interactions was demonstrated by FTIR measurements at different temperatures, as well as by rheological frequency sweep experiments. In order to mitigate the negative impact of the low molar mass PHUs and to enhance the service temperature of the adhesives, a hybrid PHU was prepared by adding a small amount of an epoxy resin, which acts as a cross-linker. These hybrid PHUs maintain the thermoreversibility displayed by thermoplastic PHUs while providing better adhesion at elevated temperatures. We believe that this work provides some important insights into the design of PHU-based hot-melt adhesives.
基于五元环状碳酸酯的聚（羟基氨基甲酸酯）（PHU）已成为传统异氰酸酯基聚氨酯的可持续替代品。然而，尽管从可持续性的角度来看它们有所改进，但其性能仍无法与传统聚氨酯相竞争。在这项工作中，讨论了PHU作为可逆热熔胶的潜力。我们发现，通过明智地选择试剂（即双环碳酸酯和二胺），部分避免了链段软段与侧链羟基之间有害的氢键作用，从而赋予PHU热熔粘合性能（即在高温下具有粘性，在低于/的温度下具有内聚性）。强调了硬段与软段比例平衡的重要性，以及扩链剂对最终性能的相关性。添加脂肪族二胺（HMDA，1,12 - DAD）会产生橡胶状材料，而使用脂环族（CBMA）或芳香族二胺（MXDA，PXDA）则会导致材料具有热熔粘合性能。通过在搭接剪切试验后重新粘结试样来评估所有组合物的热可逆性。观察到搭接剪切强度值与原始粘合剂相当。通过在不同温度下的FTIR测量以及流变频率扫描实验证明了氢键相互作用的断裂和重新形成。为了减轻低摩尔质量PHU的负面影响并提高粘合剂的使用温度，通过添加少量用作交联剂的环氧树脂制备了一种杂化PHU。这些杂化PHU保持了热塑性PHU所显示的热可逆性，同时在高温下提供更好的粘附性。我们相信这项工作为基于PHU的热熔粘合剂的设计提供了一些重要的见解。
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