Example：10.1021/acsami.1c06204 or Chem. Rev., 2007, 107, 2411-2502
Preparation of PLA with High Impact-Toughness and Reduced Internal Stress via Formation of Laminated, Bimodal Structure with Micro/Nanocells Macromolecular Materials and Engineering (IF4.367), Pub Date : 2021-09-12, DOI: 10.1002/mame.202100426 Pei Xiang, Siwen Bi, Fang Mei, Chang Deng, Dongdong Yu, Xuhang Chen, Peng Yu
The pressure-induced-flow (PIF) processing method is used to fabricate oriented, self-toughening poly(lactic acid) (PIF-PLA) with excellent mechanical properties. However, residual internal stress in PIF-PLA may lead to their deformation and cracking. Hence, to eliminate internal stress, solid-state supercritical carbon dioxide foaming (sc-CO2 foaming) is applied to PIF-PLA, with the resultant structure being called FOAM-PLA. The microstructure and mechanical properties of the PLAs are characterized pre- and post-foaming. Scanning electron microscopy results show PIF-PLA to exhibit oriented texture structures composed of staggered microfibers. Following sc-CO2 foaming, the PIF-PLA is converted into a bimodal cellular structure consisting of micro and nano-cells. According to the 2D wide-angle X-ray diffraction and Raman spectra results, this structure of the FOAM-PLA can, through a marginal reduction of orientation, release significant amounts of internal stress. Moreover, the impact strength of FOAM-PLA is found to be 32.7 kJ m−2, which is 10.2 times higher than that of crystalline PLA. This paper depicts the evolution of the PLA microstructure through the stages of PIF-processing and the subsequent solid-state sc-CO2 foaming. Meanwhile, the mechanism of the internal stress reduction is promoted.