PRINTING INK:
USE OF VISCOELASTICITY FOR QUALITY CONTROL
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PRINTING INK: USE OF VISCOELASTICITY FOR QUALITY CONTROL |
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Since the application of ink is a time dependent flow process, how it performs is closely related to its rheological properties. In printing where shear pulses are imposed on the inks, elastic effects are important and it can be misleading to evaluate the viscosity or loss modulus alone[1]. For quality control, the viscoelastic properties must be monitored so that both the storage and loss moduli are known. In the above illustration, the oscillatory shear rate dependence of two gravure inks with the same formulation but produced in two batches are presented. The rheological properties were measured in a 1 mm tube at 2 Hz and at 25°C. The loss moduli of the two batches are very similar. When either the loss modulus alone or steady flow viscosity is used as the quality control parameter, the two batches appear to be the same. However, examination of the storage modulus shows that they are very different and therefore perform differently in the printing process.
[1] Pangalos, G., Dealy, J. M, and Lyne, M. B., "Rheological properties of news
inks", Journal of Rheology, 29, 471-491 (1985).
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