抄録
The rapid cooling effect of polypropylene melt spinning reported in the previous paper, is discussed on the base of the experiments carried to investigate the influence of the force (stress) acting on a filament. The polypropylene with its molecular weight degraded by irradiation (γ-rays of Co 60) was employed to confirm the influence for the rapid cooling effect.
The force acting on a filament was given by the frictional force which was changed by the contact angle between the guide and a filament (Fig. 1). From the experimental results, it was made clear that the rapid cooling effect was greatly influenced by the force acting on a filament, immediately after it was cooled rapidly by a water bath.
It was presumed that the stress contributes the increase of molecular orientation before crystallization and the high orientation can therefore be obtained during crystallization.
On the other hand, the rapid cooling effect depends upon the molecular weight of polypropylene. The dependence of molecular weight on the rapid cooling effect, was considered in this way. In the process of rapid cooling, the polymer viscosity considered to contribute to the increase of molecular orientation before crystallization, depends upon the molecular weight, which also contributes to the increase of crystallizability (molecular movability) at low temperatures as reported in the previous paper.
