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Correlations between processing parameters, morphology, and properties of blown films of LLDPE/LDPE blends, part 2: Crystalline and amorphous biaxial orientation by WAXD pole figures



The biaxial molecular orientation of blown films made of blends of linear low density polyethylene (LLDPE) with low density polyethylene (LDPE) was characterized by two different methods: complete pole figures obtained by wide angle X-rays diffraction (WAXD) and polarized infrared spectroscopy (IR) using the Krishnaswamy approach. The molecular orientation of the blends amorphous phase was also evaluated by polarized IR. The crystallinity of the blown films was determined by WAXD. A good correlation between the X-ray pole figures and the polarized IR results was obtained. At all blends compositions, it was shown that the a-axis of the polyethylene orthorhombic cell was preferentially oriented along the machine direction, the orientation degree along this direction increasing with the increase of the LDPE amount in the blends. The b-axis changed its preferential orientation from film thickness in the 100/0 LLDPE/LDPE film to along the transverse direction with increasing LDPE in the blends. The c-axis changed its orientation from orthogonal to normal direction in the 100/0 LLDPE/LDPE film to along the film thickness with increasing LDPE in the blends. Polarized IR characterization showed a negligible orientation of the amorphous phase. The amount of crystallinity was dependent on blend composition decreasing with the increase of LDPE content in the blends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2760–2767, 2006

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