The scanning electron microscopy investigations of the morphology of the polypropylene fibes were carried out. The studies were performed for gravity spun fibres as well for fibres taken at different take-up velocities in the range from 100 to 1350 m/min. The noncoloured fibres and fibres coloured with quinacridone and phthalocyanine pigments were investigated. The studies revealed that the morphology of fibres is strongly influenced by take-up velocity and the presence of pigments. At low take-up velocity the spherulitic structure is observed. While in noncoloured fibres the big spherulites are formed in coloured fibres fine spherulites occur. In fibres coloured with quinacridone pigment spherulites possess a sheaf-like structure. The wide angle X-ray scattering measurements showed that spherulites occurred in noncoloured fibres consist of the alpha modification, whereas the sheaf-like spherulites in fibres coloured with quinacridone pigment of the beta modification. At higher velocities the spherulitic structure transforms into a fibrillar one. The fibrils possess a hierarchical structure and consist of microfibrils formed from a bundle of nanofibrils. The change of the fibres morphology was interpreted by a change of the nucleation mechanism. (C) 2003 Elsevier Science Ltd. All rights reserved.