Elucidation of polyurethane dispersions in a batch rotor-stator mixer

Abstract

In this study, the effect of high energy input from mechanical agitation, provided with a high shear rotor-stator, on the drop size and the drop size distribution (DSD) of aqueous polyurethane (PU) dispersions is investigated. The effect of the dispersed phase volume fraction (φ) on the DSD of aqueous PU dispersions is also examined to understand the fundamental characteristics that result from the high shear mixing. DSD is measured by using either a high magnification video probe or dynamic light scattering, depending on the range of drop sizes. For the PU without any ionic content, the distributions appear to be bimodal with rather large drop sizes. The mean sizes of the first and second modes are about 10 and 22 µm, respectively. For the PU with an ionic content, the mean drop sizes are approximately 80 nm. The distributions reveal that functional chemistry plays a more dominant role in the process of making PU dispersions than the mechanical agitation, and that φ has a weak effect on the mean drop sizes. The results further suggest that mechanical agitation can be used to control the breadth of the distributions.

Continuous Production of Water-Based UV-Curable Polyurethane Dispersions Using Static Mixers and a Rotor-Stator Mixer

“…This is partly in agreement with the findings of Phongikaroon et al, who indicated that mechanical stirring does not influence the mean particle size for PU dispersions. 4 Contrary to their findings, the current results also indicate that rotational speed does not affect the polydispersity. However, the particle sizes obtained in this study are 2 orders of magnitude smaller than the particles obtained by Phongicaroon, Calabrese, and Carpenter, and these PU dispersions are UV-PUDs.…”

“…However, rotor-stator mixers (RSMs) are also expected to have a significantly higher mixing intensity than the batch stirrer; therefore, it is not necessarily the processing mode (batch or continuous) that resulted in the reduced particle size and increased stability. Phongicaroon, Calabrese, and Carpenter investigated PU dispersions in a batch RSM and showed that the mechanical agitation was mainly responsible for the width of the particle size distribution . Increasing the rotational speed reduced the width of the distribution but not the mean diameter.…”

“…Phongicaroon, Calabrese, and Carpenter investigated PU dispersions in a batch RSM and showed that the mechanical agitation was mainly responsible for the width of the particle size distribution. 4 Increasing the rotational speed reduced the width of the distribution but not the mean diameter. The mean particle diameters varied between 8 and 25 μm.…”

“…Dispersion of polyurethane polymer resins and UV-curable PU polymer resins in water is made possible by either emulsifiers and/or ensuring the presence of hydrophilic structures along the polymer chain. , These hydrophilic structures are typically carboxylate groups that are ionized during the neutralization reaction. The degree of hydrophilicity will influence the emulsification process, whereby high hydrophilicity leads to smaller particles .…”

Impact of static pressure and volumetric energy input on the microstructure of food foam whipped in a rotor–stator device

“…In contrast to emulsion processing where energy plots are commonly used to directly compare measured volumetric energy input or energy dissipation rates and resulting mean bubble size (e.g. Davies, 1985;Karbstein & Schubert, 1995;Schrö der, 1999;Phongikaroon, Calabrese, & Carpenter, 2004;Lambrich & Schubert, 2005), no such publications were found for foams. The energy dissipation rate (=volumetric power input) focuses on the acting stresses only and disregards time dependency.…”