Flame retardancy properties of ammonium polyphosphate with crystalline form II by non-P2O5 process

Ammonium polyphosphate (APP) produced by non-P2O5 process and traditional P2O5 process were used in an intumescent flame retardant (IFR) polypropylene (PP) composition (IFR-PP). Rare earth oxide CeO2, in different amounts was added to study its synergistic effects in the IFR-PP material by limiting oxygen index (LOI), UL-94 and mechanical properties. TGA and SEM were used to study the decomposition processes of CeO2 added IFR-PP compositions, and to investigate its synergistic mechanism. Results showed that CeO2 could increase the LOI value of IFR-PP, maximum LOI values were found with certain amounts of CeO2. SEM demonstrated that CeO2 could promote formation of a homogenous and compact intumescent char layer. It was shown that APP by non-P2O5 process had similar IFR properties as APP by traditional P2O5 process.