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Abstract
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The microstructure and crystalline morphology of high density polyethylene (HDPE) cast films prepared in
a wide range of draw ratios (1.6 to 148.8) were investigated. The flow-induced orientation of crystalline and
amorphous phases was characterized using Fourier transform infrared spectroscopy (FTIR). The results
showed that the draw ratio has a crucial role on the orientation state of the cast films. Scanning electron
microscopy (SEM) images also confirmed this influence. The crystallinity of the films was examined using
both differential scanning calorimetry (DSC) and Raman spectroscopy. Moreover, considering a threephase
structure (i.e. crystal, amorphous and interphase) for semi-crystalline polyethylene, Raman spectroscopy
was also employed to estimate the amount of the so-called interphase in the HDPE cast films. As a
result, the interphase content was found to decrease by increasing the applied draw ratio. The origin of this
dependency was suggested to be due to a coil–stretch transition during elongation flow and the subsequent
disentanglement. On the other hand, remarkable differences were observed in the CH2 bending vibration
features of the Raman spectra of the cast films which were correlated with the applied draw ratios
and with the calculated crystalline orientation functions.
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