Study of polypropylene morphology to obtain porous membranes by stretching

Four different polypropylene resins were extruded using the tubular and the cast film processes. The morphology of the films was observed by SEM and the effect of extrusion processing variables on the morphology was investigated. Melt rheological experiments were carried out to characterize the behavior of the polymers. It was found that the molecular weight distribution and the chain structure as well as the processing conditions had important effects on the morphology. Efforts focused on obtaining a lamellar crystalline morphology by controlling the processing conditions. The possibility of generating a porous membrane from the initial morphology using a stretching technique was evaluated. The initial lamellae arrangement of the precursor film is shown to play a significant role in obtaining a porous structure.