Effects of Carbon Nanotube-Phosphorus Based Flame Retardant Combinations on Flammability of Polypropylene

Abstract

The effects of multi-walled carbon nanotubes (MWCNTs) on fire behavior of phosphorus-based flame retardant (PBFR)/polypropylene (PP) were investigated. Two different type phosphorus-based flame retardant that commercially available; ammonium polyphosphate-based (Exolit AP 760) and organic phosphorous-based (Aflammit PCO 900) powders were studied to enhance the flammability of polypropylene. Phosphorus-based flame retardant content was fixed at 8 wt% of total flame retardant (FR) formulation. MWCNTs was incorporated into FR formulation at four different concentrations (0.5 wt%, 1.0 wt%, 1.5 wt% and 2.0 wt%). All composites were prepared by melt compounding in a twin-screw extruder followed by injection molding technique. Thermal properties and flammability of the prepared samples were determined by thermogravimetric analysis (TGA), limiting oxygen index (LOI) and micro combustion calorimetry (MCC). Incorporation of organic phosphorous-based powder into PP matrix showed a better fire performance compared to ammonium polyphosphate-based flame retardant by resulting in an 11.6% higher LOI value. The LOI values decreased with the incorporation of MWCNTs into PP/ PBFR combinations; however, they still increased the thermal stability of each respective system. The addition of 2.0 wt% MWCNTs decreased the LOI value of PP/organic phosphorous-based FR system 5.2% higher than PP/ammonium polyphosphate-based FR system. The heat release rate of PP reduced in the presence of both PBFRs, but; increased with the introduction of MWCNTs.