Development of isotactic polypropylene and stearic acid-modified calcium carbonate composite: a promising material for microwavable packaging

Isotactic polypropylene (PP) composite films were developed, with incorporation of CaCO3 particles as active filler. Stearic acid was used for the surface treatment of CaCO3 to provide composite films having improved mechanical, thermal and barrier properties against oxygen as well as water vapor, in comparison to neat PP films. The filler was melt mixed with PP in a twin-screw extruder, and the films produced through melt blowing. A slight reduction in Tg values of the filled PP films was observed, along with an increase in the overall crystallization extent relative to neat PP films. X-ray diffraction data confirmed that the CaCO3 particles served as a β-nucleating agent capable of promoting the formation of the β-crystalline phase of PP and reducing the spherulite size, with stearic acid-coated CaCO3 being most effective in promoting these features. Exposing the films to microwave radiation altered their properties; at low irradiation power, the Tg values and the degree of β-crystallization were enhanced, and barrier properties against oxygen and water vapor showed improvements. In contrast, no significant changes in the appearance of the film surface were evident highlighting the potential of these PP-based composite films in microwave packaging applications.