Visualization of Polymer Adsorption on Pulp Fiber 1: Polyacrylamide, 2003 Spring Technical Conference Proceedings

A part of understanding the mechanism of strength enhancement by polymeric additives is knowing the mechanism of polymer adsorption and behavior in the wet end. A transmission electron microscopy (TEM) technique has been developed and used to visualize the differences between the adsorption patterns of various polyacrylamide derivatives on secondary fines. The objective of this research was to observe the differences in the adsorption behavior and conformational characteristics of a variety of polyacrylamide derivatives and thus validate the TEM method. The TEM micrographs show that polyacrylamides are partially adsorbed on fibril surfaces, and the unadsorbed portions of the polymer extend into the surrounding medium becoming entangled, consequently forming strands that are visible under TEM. Polyacrylamide may take the form of simple extended strands, thickened and agglomerated strands, or networked strands depending on the polymer derivative. The method is sensitive enough not only to allow differentiation between linear and branched polyacrylamide derivatives but also to observe distinctions in the adsorption behavior and conformational characteristics of linear polyacrylamides of varying molecular weights and charge characteristics.