Latex aging: The effects of coalescing agents and thermal annealing on the morphology of composite latex particles

Abstract

Many composite polymer latices are produced with nonequilibrium particle morphologies and these can be prone to structural changes with the time of storage. Here we report on the use of coalescing agents, and separately thermal annealing to follow the morphology changes with aging time. Two coalescing agents with very different water solubilities were used to plasticize the latex polymers. During months of storage time the polymer particles were analyzed via differential scanning calorimetry and transmission electron microscopy. A parallel set of aging experiments were carried out for the same latices where the change agent was simple thermal annealing. Both latex and dry polymer samples were annealed at temperatures above 100 °C and for various periods of time. Both sets of experiments lead to the conclusion that when the aging temperature is at or above the effective glass transition temperature (taking into account solvent plasticization) of the glassiest of the polymers in a two‐component latex, morphological change can be rather fast and easily characterized. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1583–1589, 2011

Hybrid Polystyrene/Polybutadiene Latexes With Low Environmental Impact

“…This was expected, because the final St conversions during the latex synthesis were high ( x ≥ 94%), and therefore the PS produced in the post‐polymerization should not importantly modify the particle morphology previously generated in the main polymerization . Also, the presence of a moderate amount of grafted copolymer, generated in the main polymerization, helps to compatibilize both phases, avoiding morphology changes, which were observed for other hybrid polymer particles subjected to thermal aging at temperatures above the polymer T g …”

“…[1] Also, the presence of a moderate amount of grafted copolymer, generated in the main polymerization, helps to compatibilize both phases, [24] avoiding morphology changes, which were observed for other hybrid polymer particles subjected to thermal aging at temperatures above the polymer T g . [25] In the latex PB 10 B 2.1 synthesized with BPO ( Figure 4), most of the particles exhibit an internal rubbery phase with multiple PS occlusions before and after post-polymerizations. In the latex PB 10 K 0.75 synthesized with KPS ( Figure 5), most of the particles are homogeneous, while hybrid particles exhibit ''core-shell'' morphologies, and this is also observed before and after post-polymerization.…”

Polymerization Induced Phase Separation in Composite Latex Particles during Seeded Emulsion Polymerization

“…We have previously shown 13 how it is quite possible to have mixed morphologies (incomplete polymer−polymer phase separation and a secondstage polymer shell) in styrene/acrylic polymerizations, particularly when the reaction temperature is near the glass transition temperatures of the polymers involved. Completely mixed systems are also quite possible 14 indicating that terminated chain diffusion and phase separation can easily be suppressed during reaction.…”

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 …”