Rheological Characterization of Liquid Colors

Despite their advantages, such as the ability to achieve homogeneous and streak-free color distribution even with minimal addition quantities, they are still often underestimated in the industry. Particularly noteworthy is their efficiency during color changes, which can be achieved with just a few cleaning cycles, resulting in a significant reduction in machine downtime.

We are very pleased with the study recently published in the journal Plastics Insights on the evaluation of liquid colors over time during storage at normal and elevated room temperatures.

The investigations were carried out by SKZ-KFE gGmbH, European Center for Dispersion Technologies (EZD), Selb, Germany, as part of the research project “Influence of carrier systems on the processing and properties of liquid-colored plastics” (FKZ: 21328 N). The EZD used the NETZSCH Kinexus rotational rheometer for this purpose.

The rheological investigations showed that the liquid colors exhibit Shear ThinningThe most common type of non-Newtonian behavior is shear thinning or pseudoplastic flow, where the fluid vis­cosity decreases with increasing shear.shear-thinning behavior. In addition, it could be observed that the flow behavior of the rapeseed oil-Carbon BlackTemperature and atmosphere (purge gas) affect the mass change results. By changing the atmosphere from, e.g., nitrogen to air during the TGA measurement, separation and quantification of additives, e.g., carbon black, and the bulk polymer can become possible.carbon black suspensions changed with increasing storage time.

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