A new flame-retardant compounds A; synthesized from phenyltrimethoxysilane (PTMS) and potassium-montmorillonite (K-MMT), B; synthesized from 3-glycidoxypropyl)trimethoxysilane (3-GPTMS) and potassium-montmorillonite (K-MMT), and C; synthesized from potassium-montmorillonite (K-MMT) that prepared by using sol-gel technique. TWIN-SCREW EXTRUDER was used to blend polypropylene (PP) with different weight percentage of polymers A, B, and C. In this paper the thermal properties of composites A, B, and C were examined by using differential scanning calorimeter (DSC). The combustion properties of the composites PP/A, PP/B, and PP/C were evaluated by the cone calorimeter (CC) at heat flux 35kW/m2. The decreasing Mass Loss Rate, Heat Release Rate (HRR), and Peak Heat Release Rate (pHRR) of the blend specimens compared to the pure PP (blank) after combustion indicated the main role of the blend composites in improving the ignition properties of the PP. Hence, the fire risk of the PP can be ignored with blending with composites A, B, and C.