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Browsing by Subject "Materials Science and Engineering"

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    Microstructure Formation of Complex Latex Coatings
    (2011-01) Crawford, Kathleen Suzanne
    Latex coatings are used throughout industry to improve properties at a surface. Understanding film formation in latex coatings is important to control coating properties. Advances in emulsion polymerization have allowed complex latex coatings to be made by combining two or more immiscible polymers into a single latex particle. The polymers phase separate within the particle, which can then form unique coating microstructures. The goal of this project is to study the film formation of complex latex coatings, using cryogenic scanning electron microscopy (cryo-SEM) in conjunction with other tools. Block copolymer latexes were synthesized at Arkema Inc. and their film formation properties were studied using cryo-SEM and AFM. The coatings complete the three stages of film formation: consolidation, compaction and coalescence. The two immiscible polymers phase separate on a scale of a few nanometers in fully formed films. The film formation of polymer latex blends was also characterized. Here, microstructure formation was studied along side with stress development and cracking. Coatings of polymer blends were shown to hold a residual tensile stress after drying completed, although lateral drying fronts convoluted results. Cryo-SEM showed cracks to form with water still present between the particles, and deformation to occur after cracking and after most of the water had evaporated. Lateral drying fronts complicated studies of film formation. To reduce or eliminate lateral drying, walled substrates were fabricated such that uniform drying could occur. Photolithography was successfully applied to create walled substrates, and coatings on walled substrates demonstrated improved uniformity.