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.

中文翻译：

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聚乳酸/聚羟基链烷酸酯/纳米原纤化的聚四氟乙烯复合材料的高发泡细孔泡沫，通过开模注塑法吹塑。

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，我们尝试设计经济上可行的材料配方以及注塑泡沫成型（FIM）工艺。众所周知，具有高膨胀性和细孔的PLA泡沫由于其固有的低熔体强度而难以在FIM技术上实现。为了克服本研究中PLA的劣质发泡特性，添加了聚四氟乙烯（PTFE）的纳米原纤维，以期望分子链缠结的增加。还将另一种生物基可生物降解的聚合物，聚羟基链烷酸酯（PHA）与PLA混合，以提高最终泡沫的冲击强度。进行了高压FIM工艺与开模技术的结合，以制造具有多种材料配方的高膨胀PLA泡沫。将恒定量（0.6 wt％）的超临界氮注入FIM系统，并与各种聚合物组合物均匀混合。将载有气体的熔体注入模腔，以产生发泡的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率和所需泡孔结构的完全可生物降解的PLA泡沫显然是可行的。