Investigations on the Film‐Formation Process of Latex Dispersions by Solid‐State NMR Spectroscopy

Abstract

Various latex dispersions based on poly(vinyl acetate) stabilised by different surfactants and polyelectrolytes were investigated by NMR methods to elucidate the macroscopic and molecular film‐formation process of these latex dispersions. Macroscopically, the inhomogeneous drying in the film‐formation process was investigated by NMR‐imaging techniques. Here the influence of different amounts of surfactant on the homogeneity of the drying process was monitored. The molecular film‐formation process was investigated by 1H, 2H, and 13C solid‐state NMR spectroscopy. For these bulk measurements, films of latex dispersions were homogeneously dried to different defined solid contents. Spectroscopic analysis allows the investigation of the drying process of the water at different solid contents with a pronounced influence on the polymer/water interface and the latex particle core. The film‐formation process is correlated to the drying mechanism of different types of water within the film. External water, water at ionic and non‐ionic groups at surfactants in the polymer/water interface, and water in the swollen and mobilised polymer, could be distinguished during the drying process.

Water Whitening Reduction in Waterborne Pressure‐Sensitive Adhesives Produced with Polymerizable Surfactants

“…During the film formation, the adsorbed surfactant can migrate toward the film–air or the film–substrate interface . Surfactants that are strongly adsorbed during the film formation process can also be trapped at particle/particle boundaries creating hydrophilic pathways in the film, and in some cases, the surfactant is pushed away from the particle/particle boundaries creating small pockets or aggregates throughout the film . As water is drawn into the film by osmotic forces, the existence of hydrophilic pockets can result in localized defects such as discoloration and blistering because the hydrophilic pockets will swell when exposed to water .…”

Drying and film formation of industrial waterborne latices

“…Currently, we are aware of only the two following experimental studies dealing with water distribution in latex films. Solid‐state nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the influence of different amounts of surfactant on the homogeneity of the vertical drying process of thick films (∼5 mm) 19. Excellent data have been obtained from magnetic resonance (MR) profiling used to monitor vertical water concentration profiles in thin films (∼300 μm) of alkyd emulsions20 and also to measure horizontal water concentration profiles resulting from inhomogeneous drying within a drop of latex dispersion 21…”

Anionic Polymerizable Surfactants and Stabilizers in Emulsion Polymerization: A Comparative Study

“…Furthermore, when the latex is applied as a film the adsorbed surfactant can migrate toward the air-film or the substrate-film interface. [5][6][7][8][9][10][11][12][13][14] During film formation, surfactants that are strongly adsorbed can also be trapped at particle/particle boundaries creating hydrophilic pathways in the film, [15,16] and in some cases, the surfactant is pushed away from the particle/particle boundaries creating small pockets or aggregates throughout the film. [10,13,17] The hetero geneous distribution of the surfactant within the film readily affects the performance of the film formed.…”