Design and preparation of new polypropylene/magnesium oxide micro particles composites reinforced with hydroxyapatite nanoparticles: a study of thermal stability, flame retardancy and mechanical properties

Abstract To improve the flame retardant efficiency of PP, a new ternary polypropylene (PP) hybride containing, micro-size magnesium oxide (MgO) and nano size hydroxyapatite (HA) particles was prepared via melt blending technique. To better distribute particles in the PP matrix and enhance the effect of flame retardancy, SABO-STAB UV94 (SABO) was mixed in MgO (SABO@MgO) and used for the preparation of the PP composite and nanocomposites. X-ray diffraction (XRD) and elemental mapping results indicated that the HA nanoparticles were uniformly dispersed in the PP matrix. According to the results of thermogravimetric analysis (TGA), the maximum mass loss temperature (Tmax) and char residue of the PP systems were increased, as compared to the neat PP. The cone calorimeter results also indicated that the total heat release (THR) of the PP nanocomposite with 20 mass% SABO@MgO and 5 mass% HA nanoparticles was decreased from 124 kJ/m2 to 102 kJ/m2, as compared to the neat PP, passing the V-0 rating at the UL-94 test. The peak heat release rate (pHRR) of the PP nanocomposite with 20 mass% MgO and 5 mass% HA nanoparticles was also decreased from 834 kW/m2 to 545 kW/m2. Further, according to the results of the tensile test, the tensile strength of the PP nanocomposite with 20 mass% MgO and 5 mass% HA nanoparticles was increased from 44.4 MPa (for the neat PP) to 54.1 MPa.