Filler blend of carbon nanotubes and organoclays with improved char as a new flame retardant system for polymers and cable applications

Multi wall carbon nanotubes (MWCNTs) or single wall carbon nanotubes (SWCNTs) were used as fillers in polyethylene (PE). Only MWCNTs reduced the heat release rates caused by polymer degradation. MWCNTs can be more effective in heat release reduction than organoclays. The char generated by the filler blend 'MWCNTs and organoclays' as a synergistic flame retardant system in an ethylene vinylacetate (EVA) based polymer blend was improved compared with the char generated by the only organoclay based nanocomposite. Initial results indicated that there was a strengthening effect of the char by MWCNTs. The synergistic improvement for heat release reduction by a blend of the two fillers 'MWCNTs and organoclays' was used for the development of a flame retardant cable compound. 1.5 kg of MWCNTs was compounded on a Buss ko-kneader to generate 60 kg of a nanocomposite based on the filler blend. The flame retardant properties of insulated wires made either by the filler blend or by 'classical' organoclays were measured. Copyright (c) 2004 John Wiley & Sons, Ltd.