The shape memory behavior of smart materials is widely used for stimulation or shape-shifting purposes. Shape memory polymers (SMPs) can shape and force recoveries accompanied by attractive attributes such as biocompatibility, biodegradability, and universality. In this paper, a thermoplastic elastomer (TPE) is used as a complementary material for 4D printed polylactic acid (PLA) structures to enhance their shape and force recovery properties and lower the stimulation temperature for more practical implementations. Two approaches are followed to provide SMP composites (SMPCs): multi-layered and multi-material lattices. In multi-layered lattices, specimens are comprised of separate layers and different ratios of SMP and TPE materials. For comparison, PLA-TPE filaments with the same ratios of multi-layered lattices are produced and used to fabricate multi-material lattices. Dynamic mechanical thermal analysis tests showed a reduction in the glass transition temperature of the manufactured PLA-TPE filament. X-ray diffraction test was conducted to prove that the crystallinity of the developed PLA-TPE material increases which explains the better shape memory effect in the multi-material specimens. Phase separation occurred in low ratios of TPE in PLA, discernible in field emission scanning electron microscope (FESEM) images, resultting in low quality in one of the developed PLA-TPE filaments. FESEM images also showed proper miscibility of TPE in PLA in higher ratios. Thermomechanical tests were done on printed specimens to examine and compare the shape and force recovery of the produced SMPCs. While the shape recovery of multi-material samples was not as good as multi-layered samples, both approaches have better shape recovery results than the PLA sample. Due to a lower glass transition temperature in multi-material lattices, their shape recovery process started at lower temperatures widening their potential practical applications. Force recovery of multi-material samples revealed a significant improvement which was due to more oriented crystalline polymer structures.

智能材料的形状记忆行为被广泛用于刺激或变形目的。形状记忆聚合物 (SMP) 可以塑造和强制恢复，并伴随着吸引人的属性，例如生物相容性、生物降解性和通用性。在本文中，热塑性弹性体 (TPE) 用作 4D 打印聚乳酸 (PLA) 结构的补充材料，以增强其形状和力恢复特性，并降低刺激温度以实现更实际的实现。遵循两种方法来提供 SMP 复合材料 (SMPC)：多层和多材料晶格。在多层晶格中，试样由不同的层和不同比例的 SMP 和 TPE 材料组成。为了比较，生产具有相同多层晶格比率的 PLA-TPE 长丝并用于制造多材料晶格。动态机械热分析测试显示制造的 PLA-TPE 长丝的玻璃化转变温度降低。进行 X 射线衍射测试以证明开发的 PLA-TPE 材料的结晶度增加，这解释了多材料样品中更好的形状记忆效应。PLA 中 TPE 的低比率发生相分离，在场发射扫描电子显微镜 (FESEM) 图像中可辨别，导致其中一种开发的 PLA-TPE 长丝质量低下。FESEM 图像还显示了 TPE 在 PLA 中以更高比例的适当混溶性。对印刷样品进行了热机械测试，以检查和比较生产的 SMPC 的形状和力恢复。虽然多材料样品的形状恢复不如多层样品，但两种方法的形状恢复结果都比 PLA 样品好。由于多材料晶格中较低的玻璃化转变温度，它们的形状恢复过程在较低温度下开始，从而扩大了它们的潜在实际应用。多材料样品的力恢复显示出显着改善，这是由于更多取向的结晶聚合物结构。