Kalia Karun, Kazmer David, Ameli Amir
Department of Plastics Engineering, University of Massachusetts Lowell, 1 University Ave., Lowell, Massachusetts 01854, United States.
ACS Appl Eng Mater. 2025 Mar 14;3(3):625-635. doi: 10.1021/acsaenm.4c00764. eCollection 2025 Mar 28.
A unique approach to 3D-print functionally graded foams (FGFs) via dynamic control of the blowing agent content is demonstrated. The approach utilizes a co-extrusion additive manufacturing process equipped with a static mixer nozzle (SMN) and thermally expandable microspheres (TEMs) as the foaming agent. The nozzle consists of two flow paths, one longer than the other, to facilitate the feeding of two different filaments. It is also equipped with layer multiplying elements (LME) for the mixing of the incoming melt streams. The first incoming filament was the expandable polylactide acid loaded with 8.0 wt % TEM (ePLA) to be mixed with the second filament made of neat PLA. The mixing of the two filaments at various ratios was successfully achieved, resulting in foams with uniform cellular morphologies at various densities. The choice of flow path also had a significant effect on the foam density. When ePLA was fed through the longer flow path, a greater degree of foaming was obtained due to a longer residence time. The FGF flexural samples, printed through this method, demonstrated a superior mechanical performance compared to their single density foam and solid unfoamed counterparts. The results reveal that this approach of foam additive manufacturing process provides a capable method to manufacture complex and functionally graded structures with programmable density profiles with specific gravities varying between 0.43 and 1.21 g cm on demand.
展示了一种通过动态控制发泡剂含量来3D打印功能梯度泡沫（FGF）的独特方法。该方法利用配备静态混合器喷嘴（SMN）和热膨胀微球（TEM）作为发泡剂的共挤出增材制造工艺。喷嘴由两条流道组成，一条比另一条长，以方便两种不同长丝的进料。它还配备了层倍增元件（LME），用于混合进入的熔体流。第一条进入的长丝是负载8.0 wt% TEM的可膨胀聚乳酸（ePLA），将与由纯PLA制成的第二条长丝混合。成功实现了两种长丝以不同比例混合，从而得到了具有各种密度且泡孔形态均匀的泡沫。流道的选择对泡沫密度也有显著影响。当ePLA通过较长的流道进料时，由于停留时间较长，获得了更大程度的发泡。通过这种方法打印的FGF弯曲样品与其单密度泡沫和实心未发泡对应物相比，表现出优异的机械性能。结果表明，这种泡沫增材制造工艺方法提供了一种有能力的方法，可按需制造具有可编程密度分布、比重在0.43至1.21 g/cm之间变化的复杂功能梯度结构。
