Cavodeau Florian, Brogly Maurice, Stumbe Jean-François, Perrin Rémi
Laboratoire de Photochimie et d'Ingénierie Macromoléculaires, Université de Haute Alsace, 3b Rue Alfred Werner, 68100 Mulhouse, France.
Soprema, 15 Rue de Saint-Nazaire, 67100 Strasbourg, France.
Polymers (Basel). 2025 Jun 27;17(13):1796. doi: 10.3390/polym17131796.
This study focuses first on the synthesis through an aza-Michael addition reaction of original linear diamine prepolymers and original amine/acrylate thermoset adhesives, and second on their thermal, mechanical and adhesion characterization. The major advantage of the aza-Michael addition reaction is that it takes place at room temperature, without a solvent and without a catalyst. Using the aza-Michael addition reaction, linear secondary diamine prepolymers were first synthesized with a control of the molecular weight, ranging from 867 to 1882 g mol. Then, aza-Michael reactions of diamine prepolymers with three different acrylates allowed the synthesis of new amine/acrylate thermoset adhesives. All the thermoset adhesives were characterized by rheology and thermal analysis, leading, once the crosslinking aza-Michael reaction had occurred, to soft thermoset networks with glass transition temperatures ranging from -23 to -8 °C, gel point times ranging from 40 min to 4 h, and a polar component of the surface energy ranging from 3 to 17 mJ m. Functionality of the acrylates directly influences the crosslinking rate, and a decreasing master curve is obtained when reporting crosslinking rate versus gel point time. Crosslinking density is controlled by the diamine prepolymer chain length. In a second step, thermoset adhesives were applied as thin films between two galvanized steel plates, and adhesion properties were evaluated through a lap-shear test. Results showed that the adhesive strength increases as the dynamic viscosity and molecular weight of the diamines prepolymer increases. Increasing the diamines prepolymer chain length results in an increase in strain at break, a decrease in the shear modulus, and a decrease in the maximum lap-shear strength. It is also observed that the adhesive strength decreases when the adhesive film thickness increases. Moreover, thermoset adhesives with high polarity and a surface energy similar to the surface energy of the substrate will favor high adhesion and a better adhesive strength of the assembly. Lastly, the nature of the acrylates and diamines prepolymer chain length allow tuning a wide range of adhesive strength and toughness of these original soft thermoset adhesives.
本研究首先聚焦于通过氮杂迈克尔加成反应合成新型线性二胺预聚物和新型胺/丙烯酸酯热固性粘合剂，其次是对它们进行热性能、机械性能和粘附性能表征。氮杂迈克尔加成反应的主要优点是它在室温下进行，无需溶剂和催化剂。利用氮杂迈克尔加成反应，首先合成了分子量可控的线性仲二胺预聚物，分子量范围为867至1882 g/mol。然后，二胺预聚物与三种不同的丙烯酸酯发生氮杂迈克尔反应，合成了新型胺/丙烯酸酯热固性粘合剂。所有热固性粘合剂都通过流变学和热分析进行了表征，一旦发生交联氮杂迈克尔反应，就会形成玻璃化转变温度在-23至-8°C之间、凝胶点时间在40分钟至4小时之间、表面能的极性分量在3至17 mJ/m之间的软质热固性网络。丙烯酸酯的官能度直接影响交联速率，当绘制交联速率与凝胶点时间的关系曲线时，会得到一条下降的主曲线。交联密度由二胺预聚物的链长控制。在第二步中，将热固性粘合剂作为薄膜涂覆在两块镀锌钢板之间，并通过搭接剪切试验评估粘附性能。结果表明，随着二胺预聚物的动态粘度和分子量增加，粘合强度增加。增加二胺预聚物的链长会导致断裂应变增加、剪切模量降低以及最大搭接剪切强度降低。还观察到，当粘合剂薄膜厚度增加时，粘合强度会降低。此外，具有高极性且表面能与基材表面能相似的热固性粘合剂将有利于组件具有高粘附性和更好的粘合强度。最后，丙烯酸酯的性质和二胺预聚物的链长使得可以调节这些新型软质热固性粘合剂的广泛粘合强度和韧性。
