Li Ming, Li Shengnan, Liu Bujin, Jiang Tuanhui, Zhang Di, Cao Lushuai, He Li, Gong Wei
The Institute of Materials and Metallurgy of Guizhou University Guiyang China.
National Engineering Research Center for Compounding and Modification of Polymer Materials Guiyang China.
RSC Adv. 2021 Oct 5;11(52):32799-32809. doi: 10.1039/d1ra06382k. eCollection 2021 Oct 4.
The inherently linear poly (lactic acid) suffers unsatisfying foaming behavior due to its low melt strength and poor crystallization properties. To overcome this drawback, a random terpolymer of ethylene, acrylic ester and glycidyl methacrylate (EGMA) was employed to improve the rheological behavior, crystallization properties, and foaming performance of poly (lactic acid) (PLA) through a chain extension reaction. The branched/micro-crosslinked structure formed by the chain extension reaction between EGMA and PLA effectively improved the dynamic rheological properties of PLA. As the content of EGMA increased from 0 wt% to 20 wt%, the crystal nucleation and crystal growth rate of various PLA samples have been significantly accelerated, resulting in a larger number and smaller size of spherulites, and the crystallinity of various PLA samples increased from 7.9% to 38.54%. The cell size of various PLA foams decreased from 53.5 to 22.0 μm and the cell density increased from 3.5 × 10 cells per cm to 2.5 × 10 cells per cm, meanwhile, the cellular morphology of PLA foam was obviously improved. Moreover, the actual weight loss of PLA foams reached 26.1%, which is higher than the theoretical weight loss.
由于其熔体强度低和结晶性能差，固有的线性聚乳酸的发泡行为并不理想。为了克服这一缺点，采用乙烯、丙烯酸酯和甲基丙烯酸缩水甘油酯的无规三元共聚物（EGMA），通过扩链反应改善聚乳酸（PLA）的流变行为、结晶性能和发泡性能。EGMA与PLA之间的扩链反应形成的支化/微交联结构有效地改善了PLA的动态流变性能。随着EGMA含量从0 wt%增加到20 wt%，各种PLA样品的晶核形成和晶体生长速率显著加快，导致球晶数量增加、尺寸减小，各种PLA样品的结晶度从7.9%增加到38.54%。各种PLA泡沫的泡孔尺寸从53.5减小到22.0μm，泡孔密度从每立方厘米3.5×10个泡孔增加到每立方厘米2.5×10个泡孔，同时，PLA泡沫的泡孔形态明显改善。此外，PLA泡沫的实际重量损失达到26.1%，高于理论重量损失。
