Wang Linlin, Zhang Fenghua, Liu Yanju, Du Shanyi, Leng Jinsong
Centre for Composite Materials and Structures, Harbin Institute of Technology (HIT), No. 2 Yikuang Street, Harbin 150080, People's Republic of China.
Department of Astronautical Science and Mechanics, Harbin Institute of Technology (HIT), No. 92 West Dazhi Street, Harbin 150001, People's Republic of China.
ACS Appl Mater Interfaces. 2021 Apr 21;13(15):18110-18119. doi: 10.1021/acsami.1c02624. Epub 2021 Apr 12.
High-performance shape memory thermosetting polymers and their composites for four-dimensional (4D) printing are essential in practical applications. To date, most printable thermosets suffer from complicated processes, poor thermodynamic performances, and low printing speed. Here, photosensitive composite inks for fast photocuring printing are developed. The inks consist of epoxy acrylate (EPAc), polyethylene glycol dimethacrylate (PEGDMA), and carbon fillers, which form a firm network structure when exposed to UV light. EPAc is synthesized via addition esterification of epoxy resin and acrylic acid under mild conditions. It is worth noting that raw materials for the reaction are diverse, including not only various epoxy resins but also molecules with epoxy groups. The 4D printing speed of up to 180 mm/h is mainly attributed to the exothermic reaction initiated by free radicals, which accelerates the polymerization of EPAc and PEGDMA. Most importantly, by increasing the exposure time of each layer from 1 s to 3 s during the printing process, the epoxy composite-infilled carbon nanotubes and carbon fibers are printed to ensure the integrity of the microlayer structure. Furthermore, we design a claw-like catcher device based on the above printable composite inks to demonstrate its potential applications in aerospace, such as grasping end-of-service spacecraft or explosive debris. Undoubtedly, 4D printing technology opens up a new portal for the manufacturing of thermoset epoxy composites and complex structures, which make the shape memory thermosetting epoxy resins and their composites possess excellent properties and good engineering application prospects.
用于四维（4D）打印的高性能形状记忆热固性聚合物及其复合材料在实际应用中至关重要。迄今为止，大多数可打印热固性材料存在工艺复杂、热力学性能差和打印速度低的问题。在此，开发了用于快速光固化打印的光敏复合油墨。这些油墨由环氧丙烯酸酯（EPAc）、聚乙二醇二甲基丙烯酸酯（PEGDMA）和碳填料组成，在紫外光照射下形成牢固的网络结构。EPAc是在温和条件下通过环氧树脂与丙烯酸的加成酯化反应合成的。值得注意的是，反应的原料多种多样，不仅包括各种环氧树脂，还包括带有环氧基团的分子。高达180毫米/小时的4D打印速度主要归因于自由基引发的放热反应，该反应加速了EPAc和PEGDMA的聚合。最重要的是，在打印过程中通过将每层的曝光时间从1秒增加到3秒，打印出了填充有环氧复合材料的碳纳米管和碳纤维，以确保微层结构的完整性。此外，我们基于上述可打印复合油墨设计了一种爪状捕获装置，以展示其在航空航天领域的潜在应用，例如抓取退役航天器或爆炸碎片。毫无疑问，4D打印技术为热固性环氧复合材料和复杂结构的制造开辟了一个新的门户，这使得形状记忆热固性环氧树脂及其复合材料具有优异的性能和良好的工程应用前景。
