Synergistic effect of carbon nanotube and clay for improving the flame retardancy of ABS resin

Synergistic effect between multi- walled carbon nanotubes ( MWNTs) and clay on improving the flame retardancy of acrylonitrile - butadiene - styrene ( ABS) resin was studied. Flammability properties measured by a cone calorimeter revealed that incorporation of clay and MWNTs into ABS resin significantly reduced the peak heat release rate ( PHRR) and slowed down the whole combustion process compared to the individually filled system based on clay or MWNTs. The flame retardancy of the ABS/ clay/ MWNTs nanocomposites was strongly affected by the formation of a network structure. Linear viscoelastic properties of the ABS nanocomposites showed that the coexistence of clay and MWNTs can enhance the network structure which can hinder the movement of polymer chains and improve flame retardancy. From transmission electron microscope analysis, MWNTs were shortened after combustion and there was no significant change in their diameters. For chars of ABS/ clay/ MWNTs nanocomposites, some MWNTs ran across between clay layers, indicating a strong interaction existed between clay and MWNTs. The existence of clay enhanced the graphitization degree of MWNTs during combustion. Clay can assist the elimination of dislocations and defects and the rearrangement of crystallites. Al2O3, one of the components of clay, acts as the catalyst of graphitization.