Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada; Dr. Foam Canada, Ontario, Canada.
Microcellular Plastics Manufacturing Laboratory, Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada; Department of Mechanical Engineering, Urmia University, Urmia, Iran.
Int J Biol Macromol. 2020 Jul 15;155:286-292. doi: 10.1016/j.ijbiomac.2020.03.212. Epub 2020 Mar 27.
To manufacture entirely biodegradable polylactic acid (PLA) foam with a high expansion ratio and a fine-cell structure, we attempted to design economically viable material recipe as well as the injection foam molding (FIM) process. It is well-known that PLA foam featuring high expansion and fine cells is challenging to achieve on FIM technique due to its intrinsically low melt strength. To overcome the inferior foaming characteristics of PLA in this study, nano-fibrils of polytetrafluoroethylene (PTFE) were added expecting an increase of molecular chain entanglements. Another bio-based biodegradable polymer, polyhydroxyalkanoate (PHA) was also blended with PLA to improve the impact strength of the final foams. High-pressure FIM process combined with mold-opening technique was performed to make highly expanded PLA foams with varied material recipes. A constant amount (0.6 wt%) of supercritical nitrogen was injected into FIM system and uniformly mixed with various polymer compositions. The gas-laden melt was injected into the mold cavity to create the foamed PLA samples. Finally, we could demonstrate that it is clearly feasible to manufacture entirely biodegradable PLA foams having a high expansion ratio and a desirable cellular structure using an advanced FIM process.
为了制造具有高膨胀比和细孔结构的完全可生物降解的聚乳酸（PLA）泡沫，我们尝试设计经济可行的材料配方和注塑发泡成型（FIM）工艺。众所周知，由于 PLA 本身的熔体强度低，在 FIM 技术上很难实现具有高膨胀率和细孔的 PLA 泡沫。为了克服 PLA 在发泡方面的劣势，本研究中添加了纳米纤维聚四氟乙烯（PTFE），期望增加分子链缠结。另一种基于生物的可生物降解聚合物——聚羟基脂肪酸酯（PHA）也与 PLA 共混，以提高最终泡沫的抗冲击强度。采用高压 FIM 工艺结合开模技术，用不同的材料配方制备高膨胀 PLA 泡沫。将一定量（0.6wt%）的超临界氮气注入 FIM 系统，并与各种聚合物成分均匀混合。将含气熔体注入模具型腔，制成发泡 PLA 样品。最后，我们可以证明，使用先进的 FIM 工艺制造具有高膨胀比和理想孔结构的完全可生物降解的 PLA 泡沫是完全可行的。
