Carbon nanoparticle reinforced polymer composites

Abstract

Theoretically, covalent functionalised carbon nanotubes (f-CNTs) are supposed to be effective reinforcement fillers to improve the mechanical properties of the brittle epoxy in a significant extent. The mechanical properties (tensile strength, Young’s modulus, etc) of the CNTs are much higher than the properties of the epoxy resins. In addition, for f-CNTs, the covalent functionalisation methods are good ways to improve the CNT/epoxy interfacial bonding strength and the miscibility of the CNTs in the epoxy. However, there is still no satisfied functionalisation method to improve the performance of the CNT/epoxy nanocomposites (NCs) in a significant content. The reason can be concluded as the conventional covalent functionalisation methods damage the CNT scaffolds so the benefits of the functionalisation are overshadowed. In this project, f-CNTs modified by a new damage-free functionalisation method, thermochemical grafting (TC) approach, were used to reinforce an epoxy. The grafting chemicals were glycidyl methacrylate (GMA) and methyl methacrylate (MMA), respectively. For comparisons, NCs reinforced by as-received (non-functionalised) CNTs and three different commercial functionalised amine-CNTs were prepared. A high shearing method to do the CNT/epoxy mixing was built and two different stirrers were used to produce NC samples separately. In the tensile tests, NCs made via a two blade stirrer were produced and tested. The NCs reinforced by 0.25wt% GMA grafted CNTs showed a better elongation property (strain improvements from the pure epoxy:18.12%) than the NCs reinforced by other kinds of CNTs (strain improvements from the pure epoxy: around 10.00% or less). Meanwhile, the commercial covalent functionalised CNTs reduced the elongations (strain reductions from the pure epoxy: 10% or higher) of the NCs. In the fracture toughness tests, NCs made via a dissolver disk were produced and tested. It was found that GMA grafted CNTs improved the model I fracture toughness of the NCs, from the pure epoxy resin, with a significant number of 16.48%. This number is higher than the other NCs. The influences of the surface functionalisation on the CNT dispersion state are discussed. In addition, the failure mechanisms of the NCs reinforced by different kinds of CNT/f-CNTs are identified and discussed.