College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Chengdu 610065, PR China.
School of Aeronautics and Astronautics, State Key Laboratory of Polymer Materials Engineering of China, Sichuan University, Chengdu 610065, PR China.
Int J Biol Macromol. 2021 Jul 31;183:222-234. doi: 10.1016/j.ijbiomac.2021.04.146. Epub 2021 Apr 27.
Long chain branching (LCB) structures are efficiently introduced into polylactide (PLA) by employing sustainable soybean oil (SO) under the initiation of trace amount of cyclic peroxide, which displays robust foamability and heat resistance. It is discovered that with the introduction of 0.6 wt% SO, the expansion ratio and Vicat softening temperature of LCB PLA are sharply raised to 75.2-fold and 155.8 °C, respectively, which is about 17.9 and 2.6 times those of linear PLA. This is because that the amounts of LCB structures are significantly increased in LCB PLA by the addition of SO with low reactivity of internal CC bonds, which can avoid the oligomerization reaction, resulting in more dramatically improved melting strength and crystallization performance of LCB PLA. Moreover, the hydrolytic degradation of LCB PLA is largely expedited as compared to linear PLA, owing to the more rapid water permeation caused by the loose packing of LCB structures. Finally, the PLA foam tray with light weight and good heat resistance is successfully developed by using LCB PLA with 0.6 wt% SO through extrusion foaming with supercritical carbon oxide and thermoforming techniques. Hence, this research offers a green route to produce eco-friendly light-weight and high-heat-resistance LCB-PLA foam with full biodegradability, which is an ideal alternative to the non-degradable oil-based plastics in the field of disposable packaging products.
长链支化（LCB）结构可通过在痕量环状过氧化物引发下利用可持续的大豆油（SO）高效引入聚乳酸（PLA）中，表现出良好的泡沫稳定性和耐热性。研究发现，引入 0.6wt%的 SO 后，LCB-PLA 的膨胀比和维卡软化温度分别急剧提高到 75.2 倍和 155.8°C，分别是线性 PLA 的 17.9 倍和 2.6 倍。这是因为 SO 的内部 CC 键反应性低，添加 SO 会导致 LCB-PLA 中的 LCB 结构数量显著增加，从而避免了低聚物化反应，导致 LCB-PLA 的熔融强度和结晶性能得到显著改善。此外，与线性 PLA 相比，LCB-PLA 的水解降解速度大大加快，这是由于 LCB 结构的疏松堆积导致水的渗透更快。最后，通过使用含有 0.6wt%SO 的 LCB-PLA 通过超临界二氧化碳挤出发泡和热成型技术成功开发了具有重量轻和良好耐热性的 PLA 泡沫托盘。因此，本研究为生产具有完全生物降解性的环保型轻质、高热抗性 LCB-PLA 泡沫提供了一种绿色途径，是一次性包装产品领域中不可降解的石油基塑料的理想替代品。
