Abstract
Surface and adhesive forces between colloidal wood particles of resin and fiber dominatethe behavior and final properties of paper and cellulose. This paper describes the use of Atomic ForceMicroscopy (AFM) to measure the interaction force between a resin �functionalized� substrate and aglass microsphere in aqueous pH-controlled electrolyte solutions at ambient temperature. The waterwetmade substrate is a hydrophobic polystyrene film coated with an extremely thin film of wood fattyand resin acids. The surface charge on the �functionalized� substrate mimics that on resin micelles,the preferred microstructure of resin in water, and the charge on the microsphere mimics that onwood fibers. AFM force curves are analyzed to the light of the balance between attractive forces -vanderWaals- and repulsive forces -electrostatic- from the classical continuum DLVO theory of colloidalforces. Force measurements show strong and persistent short-range repulsive forces at distances lessthan 100 A which are not explained by the DLVO theory. These repulsive forces that act as barriers tocontact or coagulation originate on highly ordered water in the neighborhood of the charged surfaces.The barrier size and intensity depend on the magnitude and density of the electrical charges on theinteracting surfaces, which in turn depends on their chemical composition, and on the aqueous media.Repulsion increases with pH and decreases with electrolyte concentration. AFM flat-microspherepull-off forces reveal an apparently unreported correlation between electrolyte concentration andadhesion. Adhesion increases with electrolyte concentration and size. Complex phenomena such asdusting, the release of resin upon paper use due to poor resin-fiber bondage, can thus be controlled byregulating the aqueous media during papermaking.
Highlights
Surface and adhesive forces between colloidal wood particles of resin and fiber dominate the behavior and final properties of paper and cellulose
The barrier size and intensity depend on the magnitude and density of the electrical charges on the interacting surfaces, which in turn depends on their chemical composition, and on the aqueous media
Adhesion increases with electrolyte concentration and size
Summary
Para el análisis topográfico de las superficies de substratos con y sin recubrimiento de resina y de microesferas de vidrio se utilizó el AFM Dimension 3100-240, con un barrido horizontal máximo de 100x100 μm y un desplazamiento vertical máximo de ~7 μm. Dibujo esquemático de la medición de fuerzas de interacción entre resina de madera sobre un substrato plano y una microesfera de vidrio cuya carga superficial emula la de una fibra (b). La Figura 1b muestra un dibujo esquemático de la medición de fuerzas de interacción entre resina de madera sobre un substrato plano y una microesfera de vidrio cuya carga superficial imita la de una fibra. Mayores detalles sobre la modelación de fuerzas intersuperficiales se encuentran en el apéndice A
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