| As part of a larger effort toward the fundamental understanding of processing-structure-property (P-S-P) relationships in polyolefin blown films, investigations were conducted on a variety of polyethylene (PE) blown films. The films chosen for the study were produced from different types of resins and under different processing conditions. The resins used include high-density polyethylene, low-density polyethylene, linear low-density polyethylene and metallocene linear low-density polyethylene. Model systems were composed for unambiguous study of the effect of key processing and/or material parameters. For each model system, the study focused either on one or a few factors. Comprehensive and detailed structural characterization of PE blown films was performed using transmission electron microscopy, infrared dichroism, small-angle X-ray scattering, X-ray pole figure analysis, differential scanning calorimetry, and solid-state nuclear magnetic resonance spectroscopy. The amount of crystalline and noncrystalline contents, the orientation in crystalline and amorphous phases, and the lamellar thickness distribution were studied in detail. A series of important morphological features have been revealed. Through model system studies, the results of the morphological investigations were used to comprehend the film mechanical behavior, the influence of processing conditions on film morphology, and the impact of PE molecular characteristics on the processing-structure relationship. Important mechanical properties considered include tear strength, dart impact resistance and tensile properties. Some fundamental correlations have been established between the morphological features and the mechanical properties of PE blown films. The effect of bubble stalk and heck height has been well understood through this study. This research has resulted in an improved understanding of the fundamental P-S-P relationships in PE blown films. |
