Abstract
A melt spinning experiment of polypropylene has been carried out to investigate the crystallization behavior in a running filament by x-ray diffraction curves. The stream diameter is measured as a function of distance from the spinneret by microscopic photograph, and distributions of extensional strain rate and temperature is obtained from the diameter. The results are as follows.
The variation of lattice spacing along the spinning way agrees with the temperature dependence of lattice spacing in bulk sample. The crystalline orientation factor and the fraction of a*-axis oriented crystallite are not changed throughout the crystallization process. An increase in crystallinity is completed within about 0.5 or 1 sec, and the first half of crystallization proceeds under the extensional deformation. On the assumption of isothermal crystallization, the crystallization in melt spinning is described by Avrami equation with n=1. An increase in crystallite size (D040 and D110) calculated from Scherrer equation is similar to that in the crystallinity along the spinning way. Considering the constant thickness of crystallite in the c-axis direction, the crystallite volume turns out to be directly proportional to the crystallinity.
Hence it is found that the orientation of crystallite is determined before the appearance of crystalline diffraction and the crystallization during the melt spinning is governed mainly by crystallite growth.
