Effect of nano-silica and carbon nanotubes on the rheology and flammability behavior of epoxy

Abstract

A variety of fillers may be incorporated into epoxy as an alternative to enable fiber-reinforced composites to achieve the desired performance. This study investigates the effect of incorporating silica nanoparticles, multi-walled carbon nanotubes (MWCNT), and their combination, on the rheological, thermal, flammability, and dynamic-mechanical behavior of epoxy. Thermal stability significantly improved at temperatures exceeding 450 °C by adding nanofillers, as confirmed by the integral procedure decomposition temperature (IPDT) parameter. The combination of nano-silica and MWCNT fillers yielded the highest overall stability effect (OSE), indicative of thermal stabilization, the lowest horizontal burning rate with no dripping and self-extinguishing characteristics, higher glass transition temperature, and greater reinforcement efficiency. The hybrid samples showed similar elastic modulus and hardness compared to the neat epoxy. Morphological analysis indicated the presence of some nano-silica and MWCNT agglomerates and lower interaction between the agglomerated regions and the polymeric matrix, although the hybrid exhibited more homogeneous dispersion. Furthermore, a comprehensive rheological investigation unveiled the complex features of the studied samples, including non-Newtonian behavior and notable hysteresis, especially for the hybrid composite. The results indicate a synergistic effect between silica and MWCNT incorporated into epoxy, with desirable characteristics for towpreg formulation.