Silanization and silica enrichment of multiwalled carbon nanotubes: Synergistic effects on the thermal-mechanical properties of epoxy nanocomposites

In this paper the synergistic effects of both 3-amminopropryltriethoxy silane (APTES) functionalization and silica enrichment of carbon nanotubes on thermal and thermal-mechanical properties of epoxy based composite materials were investigated. Pristine multiwalled carbon nanotubes were oxidized, functionalized with APTES and then modified with silica nanoparticles preformed through the Stober process. The FTIR, XPS and TGA analysis confirmed the occurrence of the silane functionalization and surface silica enrichment. TEM analysis showed the presence of a "bunches" morphology where silica nanoparticles aggregated around both the CNTs wall and their ends. Thermo-mechanical, thermal and flammability properties of nanocomposite containing 1 wt% of different fillers were determined and results compared to neat epoxy resin. Results showed that both the elastic and rubbery modulus increase with the addition of filler. In particular, in the rubbery region, the storage modulus of composites with silanized and silica enriched carbon nanotubes were about 240% and 285% higher than modulus of neat epoxy system. In the glassy region, a modest increment of 25% for the storage modulus was recorded. The glass transition temperature increased of about 20 °C with silica enriched carbon nanotubes alongside with a significant enhancement of the damping behavior.