An investigation on synergism of an intumescent flame retardant based on silica and alumina

Silicon-based materials appear potentially to be attractive flame-retardants because of the protective coatings formed in fire, which decreases the rate of heat release. But few reports were presented about inorganic materials, such as SiO2, Al2O3, used as additive flame-retardants. In this paper the degradation process of the intumescent system, polypropylene (PP)/Ammonium Polyphosphate (APP)-Pentaerythritol (PER), with and without SiO2, Al2O3 or blend Of SiO2 and Al2O3 was investigated by means of cone calorimetry, TGA, LOIs measured at ambient and elevated temperature (represented by a(T) and TI, respectively). For PP/APP-PER system with the blend Of SiO2 and Al2O3 a maximal synergy was observed at the highest LOI of 35.5%, 17 units higher than the virgin PP. Its excellent flame-retardance was also evidenced by the highest residue char measured from TGA and parameters (MRL, PK-HRR, etc.) from Cone calorimetry.