A facile strategy for preparation of strong tough poly(lactic acid) foam with a unique microfibrillated bimodal micro/nano cellular structure

摘要

This work reports the design and fabrication of strong tough poly(lactic acid) (PLA) foam by combining pressure-induced-flow (PIF) processing with supercritical CO2 foaming. PIF processing widened the foaming window of PLA to 40-120 ?, while supercritical CO2 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-s). Both micron and nano cells showed decreasing cells size and increasing cell density as T-s elevated. The orientation factor as well as internal stress of PLA foams decreased with increased T-s. Compared with P-PLA samples, PLA foam prepared at T-s of 40 ? 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 C=O bond from 1763 to 1766 cm(-1)). Furthermore, PLA foam prepared at T-s of 40 ? presented excellent impact strength (32.3 kJ/m(2)), tensile strength (42.0 MPa), and ductility (14.2%). The combination of PIF processing and supercritical CO2 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.

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