Characterizing coating layer z-directional binder distribution in paper using atomic force microscopy

A methodology combining high resolution atomic force microscopy (AFM) and image analysis was developed to characterize the spatial arrangement of styrene butadiene binder in the cross section of paper model coatings applied on plastic film. The latex distribution was visualized from adhesion maps obtained using pulsed force mode atomic force microscopy, and the z-directional binder profiles were calculated using image analysis techniques. A set of laboratory coated samples including pigments with various particle sizes and particle size distributions were examined using the methodology. It was found that the cross-sectional binder area fraction in paper coatings depends on the pigment packing ability, even in the absence of binder migration, resulting in latex distributions with different degrees of uniformity.