Details:
Summary:
Low Dynamic Surface Tension (DST) of printing inks and coatings is one of several very important factors responsible for good printability. The maximum bubble pressure and differential maximum bubble pressure techniques are among the most often used methods to measure the surface tension of printing inks and coatings under different dynamic conditions. Such measurements can be affected by different factors such as: surface properties of liquids and capillaries, probe immersion depth, capillary forces, viscosity and rheology, etc. Some of those factors are considered minor but some play a major role and can be responsible for significant errors. Those factors are briefly discussed in this paper with special emphasis on viscosity. The so-called viscous effect (resistance of fluid against the moving bubble) is responsible for erroneous DST data obtained for viscous liquids. A model system consisting of water/glycerol solutions of different viscosity has been selected to investigate the effect of viscosity on the dynamic surface tension measurements under different dynamic conditions and for different types of capillaries. It was found that the error due to the viscous effect increased with increasing viscosity, increasing capillary radius and decreasing bubble surface age. This error for hydrophobic capillaries was significantly lower than that for hydrophilic probes.