Lifang Tong

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.

C60 reduces the flammability of polypropylene nanocomposites by in situ forming a gelled-ball network

The thermal and flame retardancy properties of polypropylene/fullerene (PP/C(60)) nanocomposites were investigated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cone calorimetry with the C(60) loading varied from 0.5 to 2% by weight. Dispersion of C(60) in the PP matrix was characterized by transmission electron microscopy (TEM) and optical microscopy (OM). TGA and DSC results showed that the presence of C(60) could remarkably enhance the thermal property and cone calorimeter measurements suggested that C(60) could to some extent reduce the flammability of PP, with a significant reduction in peak heat release rate and a much longer time to ignition. Furthermore, the larger the loading level of C(60), the better the flame retardancy property of PP/C(60) nanocomposites. The flame retardation mechanism and corresponding model were proposed with the help of rheological measurements, TEM and x-ray diffraction. C(60) reduced the flammability of PP by trapping free radicals in the gas phase and in situ forming a gelled-ball crosslink network to improve the flame retardancy of PP in the condensed phase. Finally, this suggested mechanism was supported by the results of advanced rheological extended systems (ARES), gel content, infrared spectrum, OM, and atomic force microscopy (AFM) measurements.

THERMAL DECOMPOSITION AND FLAMMABILITY OF ACRYLONITRILE-BUTADIENE-STYRENE/MULTI-WALLED CARBON NANOTUBES COMPOSITES

Thermal and flammability properties of acrylonitrile-butadiene-styrene copolymer (ABS) with the addition of multi-walled carbon nanotubes (MWNTs) were studied. ABS/MWNTs composites were prepared via melt blending with the MWNTs content varied from 0.2% to 4.0% by mass. Thermogravimetry results showed that the addition of MWNTs accelerated the degradation of ABS during the whole process under air atmosphere, and both onset and maximum degradation temperature were lower than those of pure ABS. The destabilization effect of MWNTs on the thermal stability of the composites became unobvious under nitrogen, and the addition of MWNTs could improve the maximum degradation temperature. The heat release rate and time of ignition (tign) for the composites reduced greatly with the addition of MWNTs especially when the concentration of nanotubes was higher than 1.0%. The accumulation of carbon nanotubes with a network structure was observed and the char layer became thicker with increasing nanotubes concentration. Results from Raman spectra showed a higher degree of graphitization for the residues of ABS/MWNTs composites.