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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