Kalia Karun, Francoeur Benjamin, Amirkhizi Alireza, Ameli Amir
Department of Plastics Engineering, University of Massachusetts Lowell, 1 University Avenue, Lowell, Massachusetts 01854, United States.
Department of Mechanical Engineering, University of Massachusetts Lowell, 1 University Avenue, Lowell, Massachusetts 01854, United States.
ACS Appl Mater Interfaces. 2022 May 18;14(19):22454-22465. doi: 10.1021/acsami.2c03014. Epub 2022 May 6.
A facile manufacturing method to enable the in situ foam 3D printing of thermoplastic materials is reported. An expandable feedstock filament was first made by incorporation of thermally expandable microspheres (TEMs) in the filament during the extrusion process. The material formulation and extrusion process were designed such that TEM expansion was suppressed during filament fabrication. Polylactic acid (PLA) was used as a model material, and filaments containing 2.0 wt % triethyl citrate and 0.0-5.0 wt % TEM were fabricated. Expandable filaments were then fed into a material extrusion additive manufacturing process to enable the in situ foaming of microcellular structures during layer deposition. The mesostructure, cellular morphology, thermal behavior, and mechanical properties of the printed foams were investigated. Repeatable foam prints with highly uniform cellular structures were successfully achieved. The part density was reduced with an increase in the TEM content, with a maximum reduction of 50% at 5.0 wt % TEM content. It is also remarkable that the interbead gaps of mesostructure vanished due to the local polymer expansion during in situ foaming. The incorporation of TEM and plasticizer only slightly lowered the critical temperatures of PLA, that is, glass-transition, melting, and decomposition temperatures. Moreover, with the introduction of foaming, the specific tensile strength and modulus decreased, whereas the ductility and toughness increased severalfold. The results unveil the feasibility of a novel additive manufacturing technology that offers numerous opportunities toward the manufacturing of specially designed structures including functionally graded foams for a variety of applications.
报道了一种实现热塑性材料原位泡沫3D打印的简便制造方法。首先通过在挤出过程中将热膨胀微球（TEM）掺入长丝中来制备可膨胀原料长丝。材料配方和挤出工艺的设计使得在长丝制造过程中TEM膨胀受到抑制。使用聚乳酸（PLA）作为模型材料，制备了含有2.0 wt％柠檬酸三乙酯和0.0 - 5.0 wt％TEM的长丝。然后将可膨胀长丝送入材料挤出增材制造工艺中，以在层沉积过程中实现微孔结构的原位发泡。研究了打印泡沫的介观结构、泡孔形态、热行为和力学性能。成功实现了具有高度均匀泡孔结构的可重复泡沫打印。随着TEM含量的增加，部件密度降低，在TEM含量为5.0 wt％时最大降低50％。同样值得注意的是，由于原位发泡过程中的局部聚合物膨胀，介观结构的珠间间隙消失。TEM和增塑剂的加入仅略微降低了PLA的临界温度，即玻璃化转变温度、熔点和分解温度。此外，随着发泡的引入，比拉伸强度和模量降低，而延展性和韧性增加了几倍。结果揭示了一种新型增材制造技术的可行性，该技术为制造特殊设计的结构提供了众多机会，包括用于各种应用的功能梯度泡沫。
