Ekinci Alper, Johnson Andrew A, Gleadall Andy, Engstrøm Daniel S, Han Xiaoxiao
Wolfson School of Mechanical, Electrical and Manufacturing Engineering, Loughborough University, Loughborough, LE113TU, UK.
School of Design and Creative Arts, Loughborough University, Loughborough, LE113TU, UK.
J Mech Behav Biomed Mater. 2020 Apr;104:103654. doi: 10.1016/j.jmbbm.2020.103654. Epub 2020 Jan 25.
Polylactic acid (PLA) is a biodegradable, biocompatible and non-toxic biopolymer with good mechanical properties, and is commonly used for the additive manufacture of PLA-based biomedical devices. Such devices are available in a range of sizes and thicknesses, with smaller devices capable of being realised via additive manufacturing in just a few layers. Due to their thermal history and thermal degradation, the thermal, molecular weight and mechanical properties of each layer was different when the raw material was melted, and the in-course layer was deposited to the previous layer. This study investigated the effect of the number of layers on mechanical, thermal and molecular weight properties, and the relationship between them. Material extruded ISO 527-2 type 5A specimens with 1-, 2-, 3-, 4-, 5-, 7- and 10-layers were prepared with the cutting die. Results indicated that the degree of crystallinity was found to decrease from 8% to 0.5% with an increasing number of layers. This was likely due to different cooling rates, where the molecular weight was lowest for 1-layer and increased with the increasing number of layers until it almost reached that of the bulk material. Additionally, ultimate tensile strength and strain increased with an increasing number of layers, while Young's Modulus decreased due to heterogeneous material structure. Of all obtained results, there was no significant difference between 5- and 10-layer in terms of mechanical and thermal properties.
聚乳酸（PLA）是一种可生物降解、生物相容且无毒的生物聚合物，具有良好的机械性能，常用于基于PLA的生物医学设备的增材制造。此类设备有多种尺寸和厚度可供选择，较小的设备通过增材制造只需几层就能实现。由于其热历史和热降解，当原材料熔化并将正在成型的层沉积到前一层时，每层的热性能、分子量和机械性能都有所不同。本研究调查了层数对机械性能、热性能和分子量性能的影响，以及它们之间的关系。使用切割模具制备了具有1层、2层、3层、4层、5层、7层和10层的材料挤出ISO 527 - 2 5A型试样。结果表明，随着层数增加，结晶度从8%降至0.5%。这可能是由于冷却速率不同，其中1层的分子量最低，且随着层数增加而升高，直至几乎达到块状材料的分子量。此外，极限拉伸强度和应变随层数增加而增加，而杨氏模量由于材料结构不均匀而降低。在所有获得的结果中，5层和10层在机械性能和热性能方面没有显著差异。
