The Influence of Parameters on the Crack Formation of Pigmented Water Borne Barrier Coatings During Folding
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Doctor of Philosophy (PhD)
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Water borne barrier coatings with pigments have great potential to replace extruded polymer coatings because they can be recycled and are more likely to break down in the environment. When formed into a package, these coated papers often need to be folded, which usually leads to decreased barrier performance of the coating, but this issue is not well documented in the literature. In this thesis, the influences of pigment type, shape, and pigment volume concentration (PVC) on the water vapor transmission rate (WVTR) and fold resistance were characterized for barrier coating formulations. Some experiments include the addition of flexible pigments and latex. A finite element method-based model was developed to simulate the folding process. These simulations were compared to experimental results to better understand the key parameters that affect crack formation in water borne barrier coatings. Plate shaped pigments gave the best WVTR results before folding but tended to generate large cracks and poor water vapor barrier properties after folding. Spherical plastics pigments yielded smaller cracks than other mineral pigments that had different shapes and higher modulus. High paper thickness, coating thickness, pigment loadings, aspect ratios, and modulus were predicted by the model to increase the likelihood of a crack formation. Experiments and the model indicate that using lower modulus (more flexible) pigments improved crack resistance compared to coatings made with higher modulus kaolin. The model predicted the key trends of the results for two pigment types at various pigment loadings. Talc and glitter gave a less crack generation than kaolin and mica when folded, It may because of smaller modulus of talc and glitter. Adding a flexible latex reduced the crack formation and lead to good barrier performance even after folding. Adding pigment into latex also eliminated the blocking problem but reduced the flexibility of the coating.
Zhu, Yaping, "The Influence of Parameters on the Crack Formation of Pigmented Water Borne Barrier Coatings During Folding" (2020). Electronic Theses and Dissertations. 3319.