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.

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Cellulose nanofibrils (CNFs) have been used as reinforcing elements in optically transparent composites by combination with polymer matrices. In this study, strong, optically transparent, and thick CNF/epoxy composites were prepared by immersing two or four layers of CNF sheets in epoxy resin. The morphology of the CNF, the preparation conditions of the CNF sheet, and the grammage and layer numbers of the CNF sheets were controlled. The solvent-exchanged CNF sheets resulted in the production of a composite with high transparency and low haze. The CNF with smaller width and less aggregated fibrils, which are achieved by carboxymethylation, and a high number of grinding passes are beneficial in the production of optically transparent CNF/epoxy composites. Both the grammage and number of stacked layers of sheets in a composite affected the optical and mechanical properties of the composite. A composite with a thickness of 450–800 μm was prepared by stacking two or four layers of CNF sheets in epoxy resin. As the number of stacked sheets increased, light transmittance was reduced and the haze increased. The CNF/epoxy composites with two layers of low grammage (20 g/m2) sheets exhibited high light transmittance (>90%) and low haze (<5%). In addition, the composites with the low grammage sheet had higher tensile strength and elastic modulus compared with neat epoxy and those with high grammage sheets.

The effects of cellulose nanofibrils (CNFs) and carboxymethyl cellulose (CMC) on the shrinkage and surface characteristics of a pigment coating layer were compared. The shrinkage of the coating layer caused by evaporation of the aqueous phase during the drying process was measured using the beam-deflection method. CMC increased drying stress via rapid immobilization of the wet coating with precipitation of the CMC molecules. However, the coating that contained CNF had a much lower stress level because the coating layer experienced less shrinkage after the immobilization point and because of the diminished shrinkage characteristics of CNF in the length direction. The water-absorbent CNF formed a collapsed structure on the coating surface, resulting in lower gloss, because it was formed under low shear and dried at a low temperature. Coated paper made under high shear and at a high drying temperature showed fewer surface defects because the CNF gel structure was destroyed under the high-shear condition.

Polymer latexes have long been used as coating binders by various branches of industry due to their capacity to adhere coating components and increase the strength of the dried final coatings. In addition, these latexes have been known to affect the rheology of coating dispersions. Currently, emulsion polymerization is the most widely used method of producing polymer latexes. While the stability of these latexes is primarily provided by electrostatic repulsion between surfactants, this property also causes foaming problems during coating processes. In this research, these problems were addressed by preparing polymer-stabilized (PS) latexes that contained different concentrations of acrylic acid. Steric protection of the latexes was provided by a protective shell consisting of starch and poly­(vinyl alcohol) (PVA). The viscosity, particle size, ζ-potential, and viscoelastic behavior of the prepared latexes were investigated as a function of pH, and their surface tension and foaming tendencies were evaluated. The latexes were applied as coating cobinders in calcium carbonate and clay coating dispersions, and the viscoelastic properties, surface tensions, and foaming tendencies of these mixtures were studied. The presence of acrylic acid monomers was found to be an important factor affecting the viscosity, particle size, and ζ-potential of the PS latexes prepared in this work, which were further found to generate less foam than comparable emulsion-polymerized latexes. Finally, coating color viscoelastic properties were modified via the partial substitution of styrene–butadiene (S/B) latexes with PS latexes.