Topological structure of microporous oriented polypropylene films

According to the data of scanning electron microscopy, gravimetry, and permeability measurements, the porous structure of membrane samples obtained in a multistage process including extension of annealed polypropylene films formed at the stage of polymer melt extrusion has been studied. It has been shown that, as the cooperativity of lamella ordering (self-assembly) increases at the stage of film extension (pore formation), the topological model of the porous phase of membranes changes from model (1), i.e., a random network of channels, to model (2), i.e., oriented through flow channels. The transition between two models is controlled by the melt spin draw ratio.