Date of Award

12-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Packaging Science

Committee Member

Dr. Duncan Darby, Committee Chair

Committee Member

Dr. Robert Kimmel

Committee Member

Dr. Kay Cooksey

Abstract

Compared to the conventional Ziegler-Natta (Z-N) catalysts, metallocene (m) catalysts have recently drawn more attention in the production of polyolefins, due to its better stereo-selectivity toward the polymer structures. To use metallocene catalyzed polyolefins as the print layers on the multilayer biaxial oriented polypropylene (BOPP) films, the effects of their topography, surface morphology and chemical compositions after corona treatment on the wetting and adhesion of water-based flexo inks were studied in this work. Seven blends containing different metallocene and Ziegler-Natta polyolefins, including polypropylene (PP), linear low polyethylene (LLDPE), and propylene random copolymer (EP), were extruded as the surface print layers on the BOPP films. These films were treated to the same level using an in-line corona treater. The topography and morphology of the film surfaces were studied using atomic force microscopy (AFM) in the light tapping and hard tapping modes respectively. The chemical compositions of these surfaces were analyzed using Owens-Wendt surface energy method and the electron spectroscopy for chemical analysis (ESCA). The results obtained in this study confirmed the hypothesis proposed that corona effects (including oxidation, chain scission, crosslinking and roughening) have less influence on the surfaces of metallocene catalyzed polyolefin films than on their Z-N counterparts and the surface characteristics affecting ink wetting and adhesion vary depending on which corona effect dominants. It was also found that Z-N PP was semi-miscible with m EP, while m LLDPE was not miscible with either m EP or Z-N EP. The corona-treated films with two m LLDPE& EP blends resulted in uneven component distributions not only on the surfaces but also vertically within the print layers. Compared to the polyolefin blends, the immiscible blends created rougher surfaces which were found to improve ink wetting and adhesion to some extent. It is expected that the findings of this study can guide the selection of metallocene catalyzed polyolefins for the print layers on the multilayer BOPP films and promote the application of these materials in the flexible packaging industry.

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