Fabrication of dendrimer-like fullerene (C-60)-decorated oligomeric intumescent flame retardant for reducing the thermal oxidation and flammability of polypropylene nanocomposites

A novel oligomeric phosphorous-nitrogen-containing intumescent flame retardant poly (4,4-diaminodiphenylmethane-O-bicyclicpentaerythritol phosphate-phosphate) (PDBPP) is synthesized, and subsequently fullerene (C-60)-decorated oligomeric intumescent flame retardant, C-60-d-PDBPP, is fabricated via chemical grafting reaction and characterized. The grafting degree of C-60 is as high as 70 wt%, and C-60-d-PDBPP nanoparticles can homogeneously disperse in polypropylene matrix since the grafting process may prevent the aggregation of C-60 particles. Upon incorporating C-60-d-PDBPP, thermal oxidation degradation of polypropylene is considerably delayed. When the concentration of C-60-d-PDBPP reached 2 wt%, the initial degradation temperature (T-5: the temperature where 5wt% mass loss occurred) and maximum weight loss rate temperature (T-max) display an increase of about 72 degrees C and 80 degrees C, respectively. Moreover, C-60-d-PDBPP can remarkably reduce the peak heat release rate (PHRR) values of polypropylene, and consequently slow down the combustion process of nanocomposites. Additionally, to some extent it prolongs the time to ignition (t(ign)) and time to peak heat release rate (t(PHRR)), all of which are very important parameters for evaluating the fire retardancy of a polymeric material.