Properties of blown composite films of polypropylene/calcium carbonate and polypropylene/calcium oxide

Extrusion molding and inflation are employed on a pilot scale to fabricate two types of composite films intended for pouch applications (flexible enclosures designed to encase and protect, e.g., lithium-ion battery components). The first type comprises cast polypropylene (CPP) blended with calcium carbonate (CaCO₃) at concentrations of 2.5-5 wt%. In contrast, the second type incorporates CPP with calcium oxide (CaO) at similar concentrations. The presence of CPP, CaCO₃, and CaO is confirmed through x-ray diffraction analysis, while Fourier-transform infrared spectroscopy validates the formation of CPP/CaCO₃ (2.5-5 wt%) and CPP/CaO (2.5-5 wt%) composite films. Both the melting and crystallization behaviors of these composite films are analyzed using differential scanning calorimetry. Thermogravimetric analysis confirms that the prepared composites feature enhance thermal stability compared to the pure CPP film. Furthermore, the results demonstrate that surface morphology is affected by both the varying contents of CaCO₃ and CaO. Among the composites, CPP/CaCO₃ at 2.5 wt% and CPP/CaO at 5 wt% exhibit improved mechanical properties, indicating that they act as effective compatibilizers. In addition, for the CaCO₃ and CaO particles, the draw ratio increases with higher concentrations (5 wt%), likely due to particle concentration effects on film drawing. The water-vapor transmission rate in CPP/CaCO₃ (2.5-5 wt%) and CPP/CaO (2.5-5 wt%) composite films decreased compared to the pure CPP film, which can be attributed to increased tortuosity. Our results highlight a promising pathway for developing composite films into advanced materials, particularly as flexible enclosures for protecting and housing lithium-ion battery components in cell pouch applications.