Modification of polypropylene with nanosized alpha-Al2O3 powders prepared by the mechanochemical method

Nanosized alpha-Al2O3 powders were prepared by the mechanochemical method, with AlCl3 center dot 6H(2)O and NH4HCO3 as raw materials, the environmentally friendly starch as an effective dispersant. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were employed to characterize the ammonium aluminum carbonate hydroxide (AACH) precursor and products. The results show that nanosized spherical alpha-Al2O3 powders without hard agglomeration and with particle size in the range of 20-40 nm can be obtained by this novel and green method. Then, polypropylene (PP)/nano alpha-Al2O3 nanocomposites were prepared by melt blending in a mixer apparatus. The crystallization behavior and mechanical properties of PP/alpha-Al2O3 nanocomposites were further investigated in this study. Wide-angle X-ray diffraction (WAXD) results show that a small amount of beta-crystal of PP forms after adding alpha-Al2O3 nanoparticles. According to differential scanning calorimetric (DSC) measurement, the alpha-Al2O3 nanoparticles make crystallization temperature of PP enhanced by acting as effective nucleating agents. The tensile strength and impact strength were both improved significantly with the addition of alpha-Al2O3 nanoparticles through tensile and impact tests. Scanning electron microscopy (SEM) observation showed that the fracture surface became rougher and further confirmed the above result.