Role of Cellulose Nanofibrils in Structure Formation of Pigment Coating Layers

The dried structure of paints and coatings are important to understand. In paper coatings, pigments and binder types are known to influence this structure. The influence of a new additive such as cellulose nanofibrils (CNF) on the interaction between the coating components is not thoroughly examined. In this study, the effect of CNF on the rheology of coating color and structure formation of the coating layer was investigated and compared to that of carboxymethyl cellulose (CMC). The addition of these two rheological modifiers made the dried coating layer porous, but the working mechanisms associated with these two additives were different. CMC, which flocculated coating components, limited the rearrangement of the components, resulting in a loosely packed coating structure in wet state. CNF, which did not significantly influence the interactions between the coating components, increased effective volume fraction by absorbing water. The water absorbing characteristics of CNF expanded the dried coating structure.