Influence of pigments on supermolecular structure of polypropylene fibres

WAXS and DSC investigations of the structure of uncoloured and coloured polypropylene fibres were carried out. Two organic pigments: a phthalocyanine and a quinacridone with different nucleating abilities were used for the colouring of fibres. The fibres were formed at various take-up velocities, and heat stabilized at temperature in the range 120–160°C. It was stated, that two polymorphic forms α and β occur in uncoloured fibres spun at extrusion velocity. Fibres spun at small and medium take–up velocity contain the mesophase, whereas fibres spun at high take-up velocity contain the crystalline α-form. In the fibres coloured with a phthalocyanine the α-form occurs independently of the take-up velocity. Fibres coloured with a quinacridone contain both forms α and β. A great content of β-form occurs in fibres spun at the lowest take-up velocity. The observed changes of the structure of fibres are connected with the change of nucleation mechanism. During heat stabilization perfecting of α-form occurs. The mesophase and a hexagonal β-form transform into a monoclinic α-form. The degree of transformation depends on the stabilization temperature. For coloured fibres the structure of unstabilized fibres is more perfect and undergoes smaller changes during stabilization than the structure of uncoloured fibres.