Effect of initial crystalline morphology on properties of polypropylene cast films

Abstract

Three polypropylene cast films of different initial morphologies (only spherulitic structure, coexisting rows of lamellae and spherulites, and lamellar structure) were prepared by extrusion followed by stretching using a chill roll. The effects of the original morphology on the orientation, mechanical responses, tear resistance, and oxygen permeability were investigated. The crystallinity and crystal size distribution of the films were studied using differential scanning calorimetry (DSC). The orientation of crystalline and amorphous phases were measured using wide angle X-ray diffraction and Fourier transform—infrared. The precursor film with the lamellar morphology showed much larger crystallinity, crystalline alignment, Young’s modulus, tensile strength, and tensile toughness along the machine direction, but smaller barrier to oxygen compared to the precursors with the only spherulitic structure and coexisting rows of lamellae and spherulites. The obtained results were discussed in terms of the miocrostructure of the precursor films.