Preparation and flame retardant properties of organic montmorillonite synergistic intumescent flame retardant polypropylene

Ammonium polyphosphate (APP) and aluminium diethylphosphonate (ADP) were mixed according to the mass ratio of 4:1, compounded with dipentaerythritol (DPER) to construct a novel intumescent flame retardant (IFR), and organo-montmorillonite (OMMT) as a synergistic flame retardant, then melt blended to prepare intumescent flame retardant polypropylene (PP) composites. The flame retardancy, thermal stability, and mechanical properties of flame retardant polypropylene composites were examined using the limiting oxygen index (LOI), vertical combustion test, thermogravimetric analysis, and cone calorimetry test. The results showed that the LOI value of the flame retardant composite PP3 reached 31.3%, UL-94 reached V-0 level, the peak heat release rate (pHRR) and the total heat release (THR) decreased by 87.8% and 33.7%, respectively, compared with the original sample of PP, and the break elongation increased by 216.4% compared with that of the sample PP1 without the addition of OMMT. The findings demonstrated that adding OMMT to IFR in the right dosage can have a positive synergistic flame retardant impact.