Phase characterization and mechanical and flame‐retarding properties of nano‐CaSO4/polypropylene and nano‐Ca3(PO4)2/polypropylene composites

An in situ deposition approach was used for the synthesis of nano‐CaSO4 and nano‐Ca3(PO4)2. The nanosize particles were confirmed with an X‐ray diffraction technique. Composites of polypropylene (PP) with 0.1–0.5 wt % nano‐ or commercial CaSO4 or nano‐Ca3(PO4)2 were prepared. The transition from the α phase to the β phase was observed for 0.1–0.3 wt % nano‐CaSO4/PP and nano‐Ca3(PO4)2/PP composites. This was confirmed by Fourier transform infrared. A differential scanning calorimetry analysis was carried out to determine the thermal behavior of the nanocomposites with increasing amounts of the nano‐CaSO4 and nano‐Ca3(PO4)2 fillers. Increases in the tensile strength and Young's modulus were observed up to certain loading and were followed by a decrease in the tensile strength. A continuous decrease in the elongation at break (%) was also observed for commercial CaSO4 and larger nano‐Ca3(PO4)2. A decrease in the mechanical properties after a certain loading might have been due to the agglomeration and phase transition of PP in the composites.