Hentschel Lukas, Petersmann Sandra, Kynast Frank, Schäfer Ute, Holzer Clemens, Gonzalez-Gutierrez Joamin
Polymer Processing, Montanuniversitaet Leoben, 8700 Leoben, Austria.
Materials Science and Testing of Polymers, Montanuniversitaet Leoben, 8700 Leoben, Austria.
Polymers (Basel). 2023 Sep 16;15(18):3785. doi: 10.3390/polym15183785.
Additive manufacturing (AM) nowadays has become a supportive method of traditional manufacturing. In particular, the medical and healthcare industry can profit from these developments in terms of personalized design and batches ranging from one to five specimens overall. In terms of polymers, polyolefins are always an interesting topic due to their low prices, inert chemistry, and crystalline structure resulting in preferable mechanical properties. Their semi-crystalline nature has some advantages but are challenging for AM due to their shrinkage and warping, resulting in geometrical inaccuracies or even layer detaching during the process. To tackle these issues, process parameter optimization is vital, with one important parameter to be studied more in detail, the print envelope temperature. It is well known that higher print envelope temperatures lead to better layer adhesion overall, but this investigation focuses on the mechanical properties and resulting morphology of a semi-crystalline thermoplastic polyolefin. Further, two different AM technologies, namely material jetting (ARBURG plastic freeforming-APF) and filament-based material extrusion, were studied and compared in detail. It was shown that higher print envelope temperatures lead to more isotropic behavior based on an evenly distributed morphology but results in geometrical inaccuracies since the material is kept in a molten state during printing. This phenomenon especially could be seen in the stress and strain values at break at high elongations. Furthermore, a different crystal structure can be achieved by setting a specific temperature and printing time, also resulting in peak values of certain mechanical properties. In comparison, better results could be archived by the APF technology in terms of mechanical properties and homogeneous morphology. Nevertheless, real isotropic part behavior could not be managed which was shown by the specimen printed vertically. Hence, a sweet spot between geometrical and mechanical properties still has to be found.
如今，增材制造（AM）已成为传统制造的一种辅助方法。特别是在医疗保健行业，从个性化设计以及总体上从一到五个样本的批量生产方面都能从这些发展中受益。就聚合物而言，聚烯烃因其价格低廉、化学性质惰性以及具有导致较好机械性能的晶体结构，一直是一个备受关注的话题。它们的半结晶性质有一些优点，但由于其收缩和翘曲，对增材制造来说具有挑战性，这会导致几何精度不准确，甚至在加工过程中出现层分离。为了解决这些问题，工艺参数优化至关重要，其中一个需要更详细研究的重要参数是打印腔温度。众所周知，较高的打印腔温度总体上会导致更好的层附着力，但本研究聚焦于一种半结晶热塑性聚烯烃的机械性能和由此产生的形态。此外，还对两种不同的增材制造技术，即材料喷射（阿博格无模成型 - APF）和基于长丝的材料挤出进行了详细研究和比较。结果表明，较高的打印腔温度会导致基于均匀分布形态的更各向同性行为，但由于材料在打印过程中保持熔融状态，会导致几何精度不准确。这种现象尤其可以在高伸长率下的断裂应力和应变值中看到。此外，通过设定特定的温度和打印时间可以实现不同的晶体结构，这也会导致某些机械性能的峰值。相比之下，就机械性能和均匀形态而言，APF技术能取得更好的结果。然而，垂直打印的试样表明，仍无法实现真正的各向同性部件行为。因此，仍需找到几何性能和机械性能之间的最佳平衡点。
