Preparation of PLA with High Impact‐Toughness and Reduced Internal Stress via Formation of Laminated, Bimodal Structure with Micro/Nanocells

Abstract

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-CO 2 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-CO 2 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-CO 2 foaming. Meanwhile, the mechanism of the internal stress reduction is promoted.

Sustainable polyester vitrimer capable of fast self-healing and multiple shape-programming via efficient synthesis and configuration processing

“…The orientation is an unstable conformation state, which will lead to the formation of residual stress. 63 Once triggered by temperature, the unstable state will result in problems of warpage and shrinkage, as shown in Fig. 6(c) and (c 1 ), which are unfavorable for dimensional stability and will shorten the service life of polymer products.…”

Strengthening Interfacial Adhesion and Foamability of Immiscible Polymer Blends via Rationally Designed Reactive Macromolecular Compatibilizers

“…On the other hand, the pressure-induced flow (PIF) processing technique, 60 as a unique method to toughen polymer materials by creating an oriented microstructure, has inspired the fabrication of foams with extraordinary cell structure for a long time. 61 Hence, the combination of the cocontinuous structure, highly strengthened interfaces, and PIF processing would be very promising to create foams with new cell structures. To verify this speculation, PBAT40/PLLA60 blends with distinct cocontinuous phase structure were selected for PIF processing, followed by CO 2 foaming.…”

“…The unique cocontinuous phase with stretched shape in the PBAT40/PLLA60 blends compatibilized by DSB and LSB with appropriate ratios greatly arouses our interest. On the other hand, the pressure-induced flow (PIF) processing technique, as a unique method to toughen polymer materials by creating an oriented microstructure, has inspired the fabrication of foams with extraordinary cell structure for a long time . Hence, the combination of the cocontinuous structure, highly strengthened interfaces, and PIF processing would be very promising to create foams with new cell structures.…”

In‐situ generation of biodegradable poly(lactic acid)/poly(butylene succinate) nanofibrillar composites via a facile and cost‐effective strategy of pressure‐induced flow processing

“…where is the enthalpy of melting, is the enthalpy of crystallization, is the melting enthalpy for 100% crystallinity, that is, is 93.6 J/g 34 and is 110.3 J/g 31 …”