Synergistic effects of oxidized CNTs and reactive oligomer on the fracture toughness and mechanical properties of epoxy

The soft modifiers added to improve the fracture toughness of epoxies generally deteriorate their mechanical properties. Hence, oxidized multi-walled carbon nanotubes (O-CNTs) were added to the epoxy modified with reactive oligomer. The NCO terminated reactive oligomer acts as a cross-linker between the O-CNTs and the OH groups of the epoxies. The impact strengths of the 15 wt.% oligomer modified epoxy containing 0.5 wt.% of O-CNTs at room temperature (RT) and cryogenic temperature (CT) are enhanced by 23.6% and 69.5% compared to that of the unmodified epoxy. In addition to increasing fracture toughness, the tensile strength (TS) of the modified epoxy/O-CNTs at CT is found to be 91.7 MPa, which is comparable to that of the unmodified epoxy (92.1 MPa). Hence, the attachment of O-CNTs to the reactive oligomer modified epoxy can be an efficient approach to toughen epoxy resins without compromising their tensile properties.