Printing Ink: Gauging the Viscosity to Fine-Tune the Particle Size Calculation
Pigment particle size crucially affects the properties and quality parameters of printing inks.
Using the Litesizer 500, we measured the particle size of a highly concentrated printing ink composed of titanium dioxide. Dynamic viscosity is an integral part of the Stokes-Einstein equation, which is used to calculate particle size in DLS. Therefore, we also performed dynamic viscosity measurements using the Lovis 2000 ME viscometer coupled to a DMA M density meter. In spite of the high turbidity of the concentrated sample (observed transmittance: 0 %), DLS measurements were performed in the back angle and showed accurate and reproducible results, confirming the excellent performance of the Litesizer for these tricky samples. Particle size results calculated using the measured dynamic viscosity of the sample differed by a maximum of 10 % from the ones obtained using the solvent viscosity, pointing at a relatively limited influence of viscosity in the system and confirming the robustness of the algorithm used by the Litesizer for particle size calculation.
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