Preparation of high-modulus and high-strength isotactic polypropylene fiber by zone-annealing method

The zone‐annealing method was utilized to prepare a high‐modulus and high‐strength fiber from isotactic polypropylene. The dynamic storage modulus at room temperature of the fiber obtained reached 21 times; 1010 dyn/cm2, which corresponded to 51% of the crystal modulus along the molecular chains, 41.2 × 1010 dyn/cm2. The relationships between mechanical properties and superstructure were investigated based on results of measurements of orientation, crystallinity, tensile properties, and dynamic viscoelasticity. It was found that the excellent mechanical properties were directly attributed to the large number of tie molecules and to the high orientation of the amorphous chains. Further, the characteristics of this method were discussed compared with the results obtained by other investigators.