A closer look at the efficacy of defoamers in water-based coating formulations

 
The low evaporation rate of water coupled with its high surface tension makes water-based formulations more prone to bubble entrapment and blistering defects. Air bubbles can form during manufacturing, packaging and application using either spray or hand-roller. To prevent air entrapment and foaming, defoamers are usually added to the coating formulations. In this study, the effects of different additives on bubble formation and dissipation were studied by preparing several formulations and capturing high resolution images of a coating sprayed on glass substrates. The results of image analysis indicate that the addition of certain additives would reduce the number of both initial bubble formation and the number of bubbles that remain after 15 minutes in the wet film thickness. The quantitative analysis results enable us to precisely compare the efficacy of a wide range of defoamers available in the market. The addition of a nonionic wetting agent into the water-based polyurethane resin resulted in almost no bubble formation, which was surprisingly better than all the other defoamers evaluated in the study.