The effect of nanoperlite and its silane treatment on the crystallinity, rheological, optical, and surface properties of polypropylene/nanoperlite nanocomposite films

Polypropylene nanocomposite films containing different contents of silane treated and untreated nanoperlite were fabricated using a corotating twin screw extruder and film blowing machine. The crystallinity, rheological, optical, morphological, and surface behavior of the resulting nanocomposites are characterized. We studied the crystallization and physical dispersion of nanoperlite in the polypropylene nanocomposite using X-ray diffraction, in which we observed that the peak intensity decreases gradually with increasing filler loading for both types (treated and untreated) of nanoperlite. However, the beta-crystal phase of polypropylene was more affected in the treated nanoperlite nanocomposites. According to rheological studies, both types of nanocomposites show similar behavior at higher frequencies, and the nanoperlite type does not show any sign of effect at higher frequencies. However, in lower frequencies, they show different trends in complex viscosity. The contact angle and surface energy indicate the untreated nanoperlite nanocomposites demonstrate hydrophilic behavior, while the treated nanoperlite nanocomposites are hydrophobic. The silane treated nanoperlite improved the light transmittance and optical properties compared to the untreated nanoperlite. Finally, according to the morphological studies, the silane treated nanoperlite show better and finer dispersion in the polypropylene matrix. The results show that the silane treatment enhances the adhesion of the polypropylene/nanoperlite interfaces, suggesting the nanocomposite with 2% silane-treated nanoperlite could be a promising choice in food packaging industries.