Tensile properties and structure of polypropylene fibres spun from a blend of different polymer grades

The tensile behavior of fibres, spun from a blend of small percentage of plastic grade polypropylene with fibre grade polypropylene, was studied in relation to their structure. The spinning and drawing process was optimized in order to increase the elastic moduli of produced filament yarns. By such optimization of the process a tenacity of 0.7 GPa, an elastic modulus of 14.8 GPa and a dynamic modulus of 19 GPa were attained. From diffuse small-angle X-ray scattering the presence of voids, up to 11.5%, was established. Voidness of the fibrillar structure was confirmed with electron micrographs. In spite of the rather drastic changes in morphology the mechanical properties of high void fibrillar structures are good, indicating that the load bearing units of the filament have maintained their integrity. The improved mechanical behavior of highly drawn fibres spun from 10/90 plastic/fibre grade polymer blend is related to higher crystalline and above all to higher amorphous orientation.