Multifunctional epoxy composites modified with graphene nanoplatelets and carbon nanotubes

Abstract

Epoxies are a class of thermoset polymers which find extensive use in high performance applications. However, epoxies are inherently brittle and are poor conductors of electricity and heat, which limits their ability to be employed in functional applications. Graphene, a one atom thin two-dimensional carbon material has attracted considerable attention as a potential filler for epoxies, due to its outstanding mechanical, electrical and thermal properties. The present work discusses the multifunctional properties of epoxy polymers modified with graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs). Hybrids of GNPs and CNTs at 9:1 mass ratio were dispersed in the epoxy using three-roll milling. The distribution of the nanofiller in the matrix was fairly uniform and the dispersion quality did not change at higher concentrations. The addition of 1 wt% hybrid nanofiller resulted in an increase of more than 8 orders of magnitude in the electrical conductivity of the epoxy, while at the same time increased the fracture energy (GIC) from 85 ± 30 J/m2 to 240 ± 2 16 J/m . Analytical modelling showed an excellent agreement between the predicted and the experimental values of GIC. GNP-modified epoxies were coated onto steel substrates through a rod coating method to assess the corrosion behaviour of such coatings. Coated panels were immersed into an aqueous solution of 3.5 wt% NaCl and were exposed for a maximum of 5 days. Coating adhesion was evaluated using a tape test. Higher GNP loadings (≥ 0.5 wt%) resulted in a deterioration in the anti-corrosion performance of the coatings. Nanocarbon-modified epoxies were used as the matrices for carbon-fibre reinforced composites, which were subjected to simulated lightning current tests. Optical examination of the laminates following the tests revealed that modification with 0.5 wt% GNPs was sufficient to achieve a comparable level of lightning strike protection to the existing metal mesh technology.