Dramatic increase in electrical conductivity in epoxy composites with uni-directionally oriented laminae of carbon nanotubes

Carbon nanotubes (CNTs) felts of aligned lamellar structure were prepared by ice templating and then infiltrated by liquid epoxy resin by vacuum pressure impregnation (INCNT/EP). Conventional physical blending method was also used to prepare carbon nanotube/epoxy composite as a comparison (PHCNT/EP). Microstructal observations of INCNT/EP fracture surfaces revealed the formation of a three-dimensional (3D) framework composed of unidirectionally oriented CNTs lamellae, which lead to a dramatic increase in electrical conductivity of the composite, by 15 orders of magnitude compared to pure epoxy and by 3 orders of magnitude compared to PHCNT/EP composite. Electrical conductivity of the INCNT/EP composite reached to 0.158 S/cm at CNT loading of 1.31 wt%. Meanwhile, improvements in Young's modulus (up to 25.5%) and yield strength (up to 12.2%) of the INCNT/EP composite under compressive loadings compared to pure epoxy were obtained. It is also observed that INCNT/EP composites show stable compressive behaviour and can effectively resist the sudden decrease of stress due to its skeleton structure of CNTs lamellae after the strain of ca. 50%.