HIGH SPEED MELT SPINNING OF ISOTACTIC POLYPROPYLENE FIBERS

Abstract

An experimental study of the variation in orientation and mechanical properties in isotactic polypropylene fibres with high speed melt spinning conditions especially take up velocities has been carried out.The orientation factors in spun fibres were computed from density, birefringence and X-ray scattering measurements, and compared with mechanical properties measured from tensile testing.The following results are obtained:1) High speed melt spinning of isotactic polypropylene produced higher oriented fibres than from normal melt spinning. The fibres, however, could be strained above 350% and the initial Young's modulus were below 47g/d.2) The initial Young's modulus was rapidly increased at the birefringence of 0.019. This birefringence was almost equivalent to about 3, 000m/min of take up velocity. In this region, the spun fibres were characterized by the disappearance of the yielding point in stress-strain relations.3) It was defined the melt spinning with the take up velocities above 3, 000m/min as the high speed spinning of isotactic polypropylene. When the take up velocities were low, the density and the birefringence of the fibres were both dependent on spinning temperature, but in the high speed spinning, the birefzingence of the fibres was no longer dependent on spinning temperature. The density of the fibres was still dependent on spinning temperature or cooling rate, but was constant for the increase in the take up velocities in the region of the high speed spinning.