Chemical Engineering Journal, Vol.323, 29-36, 2017
A high heat-resistance bioplastic foam with efficient electromagnetic interference shielding
Owing to the growing awareness of sustainability, bioplastic based composites arouse considerable attention. However, the low use temperature (usually <100 degrees C) limits their applications. To improve the heat resistance and simultaneously meet the lightweight requirement for microwave shielding, a high heat-resistance crystallite, stereocomplex crystallites (sc) formed by the stereocomplexation crystallization between enantiomeric poly(t-lactide) (PLLA) and poly(D-lactide) (PDLA), was introduced into the conductive carbon nanotube (CNT)/poly(lactic acid) (PLA) composite foam. The composite foam was fabricated by a nonsolvent induced phase separation and freeze-drying method. An intriguing phenomenon occurred in the CNT/PLLA/PDLA/dichloromethane (DCM) solution upon addition of hexane, which not only induced the phase separation of mixed solution but also facilitated the formation of 100% sc in the formed crystals in the resultant CNT/PLA/DCM gel. The freeze-dried CNT/PLA foam exhibits a low foam density of 0.10 g/cm(3) and desirable specific EMI shielding effectiveness as high as 216 dB cm(3)/g. More importantly, the formation of sc with high crystallinity (similar to 45%) and the interconnected CNT conductive networks guaranteed the dimensional stability of CNT/PLA foams, only shrinking 4.3% at 220 degrees C. Our work provides a facile method to fabricate a PLA based bioplastic foam and suggests high heat resistance and efficient EMI shielding performance. (C) 2017 Elsevier B.V. All rights reserved.