Influence of nanofillers in enhancing thermal stability and flame retardancy of halogen-free polypropylene composites

K.K.G. De Silva, S. Ray, M. Taylor, D. Bhattacharyya
University of Auckland - Product Accelerator, NZ

Keywords: nano-fillers, polymeric ammonium polyphosphate, halogen-free fire retardants, exfoliation, intercalation

Summary:

Halogen-free fire retardant polypropylene (PP) composites, based on a heat stabilized polymeric ammonium polyphosphate (AMP) and nano-fillers with good mechanical properties have been developed. Some mineral filled PP composites did not demonstrate synergistic improvements in flammability but their presence was advantageous to delay the ignition of fire and offset the melt dripping tendency by way of forming thick char barriers. Nano-talc filled PP composites provided excellent flame retardancy and thermal stability as well as enhanced mechanical strength. These PP composites showed swelling and formation of carbonaceous chars and achieved UL-94-V-0 rating where talc acts as a nucleating agent and thermal sink and reduce the fuel content. XRD and SEM studies indicated possible exfoliation, intercalation and homogeneous dispersion of talc platelets during processing. Even at low talc loadings, the composites displayed high flexural modulus while maintaining the low density. The samples passed the IEC glow-wire test and the IEC glow-wire flammability index useful for material manufacturer and end users. The commercialization of this work has been initiated by the MBIE –NZ Govt. funded Materials Accelerator program with the manufacturing industries in New Zealand.