A Scanning Electron Microscope Study of the Surface Structure of Mineral Pigments, Latices and Thickeners used for Paper Coating on Non-absorbent Substrates

We investigate the structure of coating layers prepared on non-absorbent substrates using a bench coater, composed of mineral pigments, latex binders and polymeric thickeners and dispersants, using scanning electron microscopy (SEM) that are typical of those used in paper coatings. The main aim of the study is to identify how systematic variations in the composition of the coating, including pigment type (calcium carbonate, clay), the glass transition temperature of the binder, and type (CMC, EHEC) and molecular weight of the polymeric thickener affect the surface features of the coating layer, including surface roughness and porosity and, consequently, gloss. The samples are investigated mainly in conventional high-vacuum SEM mode; however some studies are also performed with the environmental feature (ESEM mode) at higher pressures and humidities, in order to track dynamic changes due to drying and rewetting. The results are compared to those of recent measurements on the same systems obtained with atomic force microscopy (AFM), where the local latex film formation process has been carefully studied

Pressure Filtration of Cellulose Fibres

The compressional rheology of cellulose fibre suspensions has been studied using a pressure filtration technique. The dewatering of these systems is described in terms of various key properties of the suspension, including the compressive yield stress, permeability and solids diffusivity, permitting a quantitative characterization of the consolidation process. We investigate, as a particular example, the effect of a commercial debonding agent additive on the compressional properties of a fibre suspension. Such agents are used commonly in the production of hygiene products where they are added to decrease the strength of fibre-fibre bonds. Here, we investigate their effect on the compressive response of fibre suspensions as an example of how measurements of this type can be used to characterize the effect of additives on bulk properties. The results indicate that the addition of debonder lowers the dewatering tendency for a broad range of fibre concentrations, and leads to the formation of flow channels in the compressed fibre suspension