It often fails in performance differentiation when comparing the effect of paint additives on drying. In practice, this method is not reproducible and consistent due to non-standardized factors, such as the force applied during brushing, among other things. The current ASTM D7488 method relies on subjective visual assessment of repainted marks on drawdown paint film. This part of the painting process is still a challenging task due to the lack of an objective and stable method for its evaluation. This is particularly relevant for the identification of additives for the prolongation of open time, which refers to the period of time remaining after paint application to make corrections, without leaving visible defects in the film. In addition to sophisticated analysis, we still see the need for a simple and easily accessible method which allows for quantitative differentiation of drying behavior of aqueous paints and, moreover, one that will help formulators to select the most favorable ingredients for specific products and applications. Among the technical challenges that have arisen due to the switch from solvent to waterborne paints - driven by the regulatory push towards a more sustainable coatings industry - the control over the drying and film forming process of paint dispersions has been a matter of intense investigation in recent years.Īdvanced analytical methods and imaging techniques have been used to gain insights into the mechanisms driving the film forming process and to identify factors which influence open time.
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