A fluorescence approach to investigate repartitioning of coalescing agents in acrylic polymer emulsions

Abstract

Repartitioning of co-solvents between particles of latex emulsions was investigated by means of a fluorescence method based on the detection of the amount of co-solvent via the solvatochromic shift of the emission maximum of a fluorescent probe, copolymerized at a low concentration. Complete repartitioning of co-solvents between particles of latex materials with a low Tg (ca. 25 °C) occurred within minutes. For a hydrophilic latex with a Tg of 68 °C, equilibration was achieved within an hour. Repartitioning was faster for more hydrophobic co-solvents. For a hydrophobic latex of similar Tg, co-solvent repartitioning took place on the same time scale, but complete equilibration was not reached. Possibly, there is an additional slow component in the repartitioning, or the prolonged presence of co-solvent causes a structural change in the latex particles that affects the outcome of the experiment.

Drying and film formation’s first steps in polymer dispersions – Insights from a parallel gravimetric experiment and profile NMR study

“…For the present study, profiling NMR and gravimetric experiments were run in parallel using two drying cells situated right next to each other. Film-formation of two dispersions for wall-paint applications was studied with and without addition of a film-forming or coalescing agent [8]. Such co-solvents are added to many water-based coating formulations to promote better filmformation in the drying process.…”

“…Signal decay curves obtained in conventional TD-NMR measurements at 20 MHz by means of a solid echo followed by a CPMG sequence[8]. The shaded region corresponds to the CPMG echo time in the profile NMR experiments.…”

Influence of coalescing aids on the latex properties and film formation of waterborne coatings

“…The addition of coalescing aids is a convenient and flexible way of solving the so‐called film‐formation paradox and has been a subject of many research articles. The effects of coalescing aids have been studied by researchers in terms of partitioning in the wet stage and T g reduction, dispersion stability and viscosity, polymer interdiffusion, and film formation in general …”