Applied Mechanics and Structure Safety Key Laboratory of Sichuan Province School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 610031, P. R. China.
Soft Matter. 2018 Mar 7;14(10):1879-1886. doi: 10.1039/c7sm02362f.
3D printing of epoxy-based shape memory polymers with high mechanical strength, excellent thermal stability and chemical resistance is highly desirable for practical applications. However, thermally cured epoxy in general is difficult to print directly. There have been limited numbers of successes in printing epoxy but they suffer from relatively poor mechanical properties. Here, we present an ultraviolet (UV)-assisted 3D printing of thermally cured epoxy composites with high tensile toughness via a two-stage curing approach. The ink containing UV curable resin and epoxy oligomer is used for UV-assisted direct-ink write (DIW)-based 3D printing followed by thermal curing of the part containing the epoxy oligomer. The UV curable resin forms a network by photo polymerization after the 1st stage of UV curing, which can maintain the printed architecture at an elevated temperature. The 2nd stage thermal curing of the epoxy oligomer yields an interpenetrating polymer network (IPN) composite with highly enhanced mechanical properties. It is found that the printed IPN epoxy composites enabled by the two-stage curing show isotropic mechanical properties and high tensile toughness. We demonstrated that the 3D-printed high-toughness epoxy composites show good shape memory properties. This UV-assisted DIW 3D printing via a two-stage curing method can broaden the application of 3D printing to fabricate thermoset materials with enhanced tensile toughness and tunable properties for high-performance and functional applications.
3D 打印具有高机械强度、优异热稳定性和耐化学性的基于环氧树脂的形状记忆聚合物对于实际应用是非常理想的。然而，一般的热固性环氧树脂很难直接打印。虽然已经有一些成功打印环氧树脂的例子，但它们的机械性能相对较差。在这里，我们提出了一种通过两阶段固化方法利用紫外光（UV）辅助 3D 打印具有高拉伸韧性的热固性环氧树脂复合材料的方法。含有可 UV 固化树脂和环氧树脂低聚物的油墨用于 UV 辅助直接墨水写入（DIW）的 3D 打印，然后对含有环氧树脂低聚物的部件进行热固化。在第一阶段的 UV 固化后，可 UV 固化树脂通过光聚合形成网络，可在高温下保持打印结构。环氧树脂低聚物的第二阶段热固化生成具有高度增强机械性能的互穿聚合物网络（IPN）复合材料。结果发现，通过两阶段固化制备的打印 IPN 环氧树脂复合材料具有各向同性的机械性能和高拉伸韧性。我们证明了通过这种两阶段固化方法制备的 3D 打印高韧性环氧树脂复合材料具有良好的形状记忆性能。这种通过两阶段固化的紫外光辅助 DIW 3D 打印方法可以拓宽 3D 打印技术的应用范围，用于制造具有增强的拉伸韧性和可调性能的热固性材料，以满足高性能和功能应用的需求。
