Probing the morphology of polypropylene fibres by scanning probe microscopy

This paper highlights the application of scanning probe microscopy, notably atomic force microscopy in contact mode supported by lateral force microscopy, to the investigation of changes in the morphology of polypropylene (PP) monofilaments during melt-extrusion and subsequent drawing. A gradual deformation at the fibre surface from a spherulitic structure to a shish-kebab type structure is observed for the gravity spun and as-spun variants. In the drawn PP filaments, the surface structure is predominantly fibrillar in character, though the nature of the fibrillar structure is influenced by the drawing conditions. Wide angle X-ray scattering analysis, in conjunction with SPM, indicates contrasting features of surface and bulk crystal structure both at the as-spun and drawn stages of production. In addition, an unusual WAXS diffraction pattern is observed for the cold drawn PP filament. Studies of the bulk structures of the fibres by investigating fibre cross-sections using SPM will be the subject of a companion paper.