Description:
Previous real time studies during the fabrication of a blown film have reported that the imparted molecular orientation is dependent not only on the stresses acting at the freeze line but also on the crystallization process that takes place along the axial distance. In this study, the relationship between the crystallization kinetics, as estimated using real-time Raman spectroscopy measurements, and the film morphology was investigated for linear low-density polyethylene (LLDPE) blown films. Crystallization half-time (t0.5), defined as the time taken for the polymer to reach 50 % of its equilibrium crystallinity, was proposed as a single parameter to relate the processing conditions with the orientation of the films. The results showed an asymptotically decreasing relationship between crystallization half-time and the a-axis orientation factor for a range of processing conditions.