High modulus/tenacity filaments from blends of different molecular weights of polypropylene

Polypropylene (PP) filaments are prepared by blending two different molecular weight components of PP. A melt‐spinning process to produce filaments includes mixing of components, extrusion, and two‐stage drawing, followed by a unique Gradient Drawing™ process. Blending results in highly deformable as‐spun filaments with high draw ratios. For 90:10 blends of PP samples with melt flow indexes of 35 and 3, a high level of crystallinity and crystalline and amorphous orientations are obtained. A sonic modulus of 28 GPa, dynamic modulus of 20 GPa, tensile modulus of 16 GPa, and tenacity of 667 MPa are achieved. These samples are dimensionally stable up to ∼100°C. All steps in the production of the filaments are continuous. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1021–1028, 2005