Electrically conductive polycarbonate/carbon nanotube composites toughened with micron-scale voids

Electrically conductive polycarbonate (PC)/carbon nanotube (CNT) composites were prepared by melt compounding. Well-controlled voids were introduced into the PC/CNT composites by supercritical CO2 foaming technique. The dispersion of CNTs and the cellular morphology of the PC composite foams were characterized with transmission electron microscopy and scanning electron microscopy, respectively. The results reveal that the well-dispersed CNTs optimize the cellular structure of the PC foams due to their heterogeneous nucleation effect. The introduction of numerous voids endows the PC composites with comparable or even higher electrical conductivity and electromagnetic interference shielding properties. Interestingly, the presence of the voids makes the brittle PC/CNT composites tough, evidenced by the greatly improved tensile toughness and notched impact strength. The highest specific toughness for PC/1 wt% CNT composite foam is 35.3 (kJ/m2)/(g/cm3), 435% higher than that of neat PC, and 667% higher than its bulk counterpart. This work provides an efficient approach for the preparation of lightweight, tough and functional polymer composites. The influences of porosity, loading of CNTs, and cellular structure on the notched impact strength of the composites are investigated and the toughening mechanisms are discussed.