Crystallization behavior and tensile performance of nanoparticle-filled polypropylene composites

Polypropylene nanocomposites containing 1-5 wt% of nano alpha-alumina particles are prepared using a Hake internal mixer. Mixing of nano alpha-alumina particles is performed at 170 degrees C and 50 rotational per minute is set for the rotor speed. To improve the dispersion of the nanoparticles, sodium dodecylbenzenesulfonate is used. X-ray analyses reveal that the basal spacing of polypropylene/nano alpha-Al2O3 composites compared to the pure polypropylene spreads out. The peak intensity for polypropylene /nano alpha-Al2O3 composites is stronger and narrower with larger amounts of the nano alpha-Al2O3 filler, in comparison with the virgin polypropylene. According to differential scanning calorimetry, the crystallinity of the nanocomposites is increased with increases in nano alpha-Al2O3 filler loading. The storage and loss modulus of the nanocomposites are found to be higher than that of pure polypropylene, because nanofiller increases the stiffness of the nanocomposites. The tensile strength and tensile modulus of the polypropylene nanocomposites are slightly improved up to 4% of nano alpha-Al2O3 particle filler adding. The addition of filler content higher than that amount leads to the reduction of these properties. The formation of filler agglomeration site within the matrix body affects the decreasing of properties. Transmission electron microscopy observations confirm these results.