Hubei Provincial Key Laboratory of Green Materials for Light Industry, Collaborative Innovation Center of Green Light-weight Materials and Processing, School of Materials and Chemical Engineering, Hubei University of Technology, Wuhan, Hubei 430068, China.
National Engineering Research Center of Novel Equipment for Polymer Processing, The Key Laboratory of Polymer Processing Engineering of Ministry of Education, South China University of Technology, Guangzhou 510640, China; State Key Laboratory of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, China.
Int J Biol Macromol. 2022 Feb 28;199:264-274. doi: 10.1016/j.ijbiomac.2021.12.187. Epub 2022 Jan 7.
This work reports the design and fabrication of strong tough poly(lactic acid) (PLA) foam by combining pressure-induced-flow (PIF) processing with supercritical CO foaming. PIF processing widened the foaming window of PLA to 40-120 °C, while supercritical CO foaming released the undesired internal stress of PLA samples with PIF processing (P-PLA). The prepared PLA foams displayed a unique microfibrillated bimodal micro/nano cellular structure which is strongly affected by saturation temperature (T). Both micron and nano cells showed decreasing cells size and increasing cell density as T elevated. The orientation factor as well as internal stress of PLA foams decreased with increased T. Compared with P-PLA samples, PLA foam prepared at T of 40 °C showed negligible reduction of orientation from 0.45 to 0.41 and release of internal stress characterized by the rightward shift of Raman peak (stretching vibration of CO bond from 1763 to 1766 cm). Furthermore, PLA foam prepared at T of 40 °C presented excellent impact strength (32.3 kJ/m), tensile strength (42.0 MPa), and ductility (14.2%). The combination of PIF processing and supercritical CO foaming provides a facile and effective method to prepare strong tough PLA foam that has immense potential in biomedical, aerospace, automotive, and other structural applications.
这项工作报道了通过结合压力诱导流动（PIF）处理和超临界 CO2 发泡来设计和制造高强度坚韧的聚乳酸（PLA）泡沫。PIF 处理将 PLA 的发泡窗口拓宽至 40-120°C，而超临界 CO2 发泡则释放了经过 PIF 处理的 PLA 样品中的不良内应力（P-PLA）。所制备的 PLA 泡沫呈现出独特的微纤维化双峰微/纳米多孔结构，强烈受饱和温度（T）的影响。微米和纳米孔均随着 T 的升高而呈现出孔尺寸减小和孔密度增加的趋势。PLA 泡沫的取向因子和内应力随着 T 的升高而降低。与 P-PLA 样品相比，在 T 为 40°C 时制备的 PLA 泡沫的取向度从 0.45 降低到 0.41 的变化可以忽略不计，并且内应力的释放表现为 CO 键伸缩振动峰（从 1763 到 1766cm）的右移。此外，在 T 为 40°C 时制备的 PLA 泡沫表现出优异的冲击强度（32.3kJ/m）、拉伸强度（42.0MPa）和延展性（14.2%）。PIF 处理和超临界 CO2 发泡的结合为制备高强度坚韧的 PLA 泡沫提供了一种简便有效的方法，这种泡沫在生物医学、航空航天、汽车和其他结构应用领域具有巨大的潜力。
