Printing Ink: Gauging the Viscosity to Fine-Tune the Particle Size Calculation
Pigment particle size affects the quality of printing inks. Using the Litesizer DLS 500, the particle size of concentrated ink composed of titanium dioxide was tested. Dynamic viscosity as part of the Stokes-Einstein equation was determined with Lovis microviscometer coupled to a DMA density meter.
Printing inks are made of pigments or dyes that give the ink its color. Pigments are insoluble, particulate colorants whose particle size is usually in the micron range, and have either an organic or inorganic origin. The measurement of pigment particle size is an excellent predictor of the final product’s performance. In fact, it is often assumed that problems like poor color strength and shade derive from poor raw material quality; instead they are rather due to the particle size distribution. Properties like flocculation, tint strength, transparency, viscosity and stability are dependent on particle size and can thus be optimized.
The Anton Paar Litesizer DLS 500 particle analyzer served to measure the particle size of ink samples using its optical back angle configuration, which enables the particle size measurement of highly turbid and highly concentrated samples. In order to demonstrate the importance of using accurate dynamic viscosity values for particle size calculation, the viscosity of the sample was measured with Anton Paar Lovis microviscometer and it was evaluated how this parameter affects the DLS results. The Lovis microviscometer is a rolling ball viscometer that determines run times of a ball in a sample filled capillary. The run times are then converted to viscosity values using the density of the ball and of the sample. In order to measure both density and viscosity in a single run, the Lovis microviscometer was coupled with a DMA density meter.
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