Foaming and Crawling of Aqueous Industrial Coatings

Abstract

As interest in water-based industrial coatings increases, it has become apparent that problems of bubble entrapment and poor wetting of substrates are more prevalent with these finishes as compared to solvent-based systems. This paper deals with some aspects of both application problems.

A brief review of substrate wetting and defoaming theory is presented which emphasizes the importance of surface tension consideration in both phenomena. Theory also suggests that the solubility of the additive in the system can be an important factor governing the efficiency of both defoamers and anti-crawling agents. Defoamers should have a relatively low degree of solubility, while anti-crawling agents should be relatively high in solubility.

In order to document the importance of additive solubility, three typical aqueous industrial coating formulations were prepared with varying ratios of water to organic coupling solvents. Two commercial additives, a defoamer and an anti-crawling agent, known to differ in solubility, were evaluated for efficiency in these systems.

The experimental results confirmed the importance of additive solubility as a factor governing the efficiency of both defoamers and substrate wetting agents.