Structure Property Relationships in Polyethylene Blown FIlms

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Kannan, Abhiram
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The fabrication of blown films is a complex industrial process that has received some attention in the past from both industry and academia with the intention to establish detailed property-structure-processing linkages between polymers and their resulting blown films. Unfortunately, a clear understanding of the molecular level architectural variables, which control important properties of blown films such as resistance to tear and the resistance to puncture, are not fully developed. The current work uses powerful synchrotron based in situ X-ray scattering techniques to explore the morphologies of blown films as well as morphological evolution under uniaxial strain, for a series of polyethylenes whose architectures are well understood. Firstly, a number of protocols based on traditional analyses of X-ray scattering are developed which aid in the quantification of both the crystalline and non crystalline phases of the overall semicrystalline morphology of films. The analysis protocols developed allow the parametrization of dimensionality and orientation for both these phases at atomistic and mesoscopic length scales. Secondly, empirical relationships are established between the pertinent extracted parameters and molecular architectures of the polyethylenes under investigation. This enables the elucidation of those aspects of the molecular architecture of polyethylene the targeted manipulation of which is likely to result in the attainment of desired tear and puncture properties in blown films. Thirdly, quantitative relationships relating the dimensional and orientational parameters to the tear and puncture resistance properties are developed to determine the origin of these properties. Complementing the central theme of this dissertation are studies on the modeling of semicrystalline microstructures and the theoretical simulations of X-ray scattering from the same. Supplementing the analyses protocols developed from the traditional understanding of scattering phenomena are statistical analyses of scattering based on concepts borrowed from the realm of big-data analytics.
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