Carbon nanotubes (CNT) are of great interest as reinforcement materials in polymer matrix composites (PMCs) due to their exceptional tensile properties. However, the tensile properties of bulk CNT materials, such as yarns or sheets, are significantly poorer than those of the individual nanotubes due to weak inter-CNT interactions. Our group has examined covalent modification and crosslinking as a method to increase the tensile properties of bulk CNT materials. For example, CNT sheet functionalized with 3 mol % amine groups exhibited a specific tensile strength of 205 + 22 MPa/(g/cc); approximately a 65% improvement over the 127 + 11 MPa/(g/cc) value for the non-functionalized sheet. The specific modulus of the amine functional sheet was 2.59 GPa/(g/cc), compared to 0.78 GPa/(g/cc) for the non-functionalized. This trend was not retained in our initial experiments using these functionalized CNT sheets to prepare 50/50 wt% composites with epoxy thermoset resins. PMCs prepared with the amine functionalized sheet had a specific tensile strength of 141 +37 MPa/(g/cc) and specific tensile modulus of 3.22 + 0.62 GPa/(g/cc), versus 198+ 49 MPa/(g/cc) and 6.81 + 1.03 GPa/(g/cc) for composites prepared using the non-functionalized sheet. This presentation will examine our efforts to improve the tensile properties of PMCs prepared using these functionalized CNT sheet materials. The purpose of the functional groups is to enhance both the CNT-CNT interactions as well as the CNT-matrix interactions. PMCs from sheets bearing different densities of amine or epoxide functionalities are being prepared to determine the optimal degree of functionalization. Two different commercially available matrix polymers, epoxy and polybenzoxazine, are being tested.

Polymer matrix composites using covalently modified carbon nanotube sheets

249th National Meeting (2015)

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