Failure prediction of waterborne barrier coatings during folding

Adding pigments into waterborne barrier coatings improves barrier properties and cost-effectiveness but increases the risk of crack formation during folding. Crack formation is affected by pigment shape, aspect ratio, and concentration; however, the exact mechanism for these effects is still not well understood. In this work, a systematic model was used to understand the influence of the paper and coating thickness, the latex and pigment modulus, the pigment shape and aspect ratio, and pigment concentration on the failure of waterborne barrier coatings during folding. A finite element method-based model was solved with a commercial package to simulate the folding process. These simulations were compared to experimental results to verify the key parameters that affect coating failure. High paper and coating thickness, pigment loadings, pigment aspect ratios, and modulus differences between latex and pigment increased the likelihood of failure. Experiments and models using lower modulus spherical plastic pigments were more difficult to fail than coatings made with higher modulus kaolin. The maximum strain for coatings bent to a set curvature was the smallest when the modulus of latex and pigment were similar. The model agreed closely with experimental results for two pigment types at various pigment loadings.