Dynamic monitoring of tannin-based foam preparation: Effects of surfactant

Abstract

Three tannin-based foam formulations differing in the type of surfactant added were tested during foaming via simultaneous monitoring of the variation in temperature, foam rising rate, internal foam pressure, and dielectric polarization, the latter being a direct measure of the setting and curing of a thermosetting foam. This monitoring is an effective descriptor of the process and possible characteristics of the foam being prepared and constitutes an invaluable tool for foam formulation. The addition of a surfactant was shown to have a major effect on foam dynamics by retarding the onset of cross-linking to a lesser or greater extent in relation to the peak of maximum temperature in self-blowing foams. Cationic surfactants, or non-ionic surfactants capable of transforming into cationic species under the acidic environmental conditions used for tannin-based foams, were found to retard cross-linking more markedly than did non-ionic surfactants.