ON-SITE SURFACE AND WETTING TENSION MEASUREMENTS OF WATER-BASED COATINGS AND SUBSTRATES

摘要

Instruments located adjacent to formulation or process sites must be simple to use, be capable of both dynamic and static surface tension measurement, and not be effected by contaminants and any adverse site conditions. The Tensiometer described accommodates these constraints with no other requirements than a workbench, computer or laptop and a nitrogen or dry air tank. This Tensiometer measurement technique is based on a patented modification of the maximum bubble pressure method. The instrument measures maximum differential bubble pressure at the orifices and calculates the fluid surface tension. Bubbling within the body of the test fluid makes the system immune to surface contaminants and surface foam. The Tensiometer is calibrated by pre-testing two fluid standards of known surface tension values, such as deionized water and alcohol. Immersing the probes in the middle of a sample is the extent of the expertise demanded of the user. Surface tension values are used to compare the quality of newly formulated coatings against previously measured coatings. DLS wetting tensions are used to determine and compare new versus previously used substrates. Three dimensional characterization of test fluids affords formulators a complete overview of the impact of surfactant utilization as a function of surfactant concentration and speed of application (surface age). Dynamic surface tension curves for a series of water-based coatings and other formulations with active surfactants, using data generated by the Tensiometer, are illustrated in Figures 4 and Table Ⅱ. Formulations that exhibit both low equilibrium and low dynamic values can be determined prior to their use.