Influence of formulation on the dynamics of preparation of tannin-based foams

The foaming dynamics of five different tannin-based foams were followed by simultaneously monitoring the variation of temperature, foam rising rate, internal foam pressure and dielectric polarisation, this latter being a direct measure of setting and curing of a thermosetting foam. This approach to foam monitoring describes well the process and possible characteristics of the foam prepared. It constitutes an invaluable tool for foam formulation. For self-blowing foams it was shown that coordination between the foaming action and resin cross-linking must be respected. Thus, the findings indicate that to prepare a proper hardened foam cross-linking must start at the same time the temperature and the internal pressure reach their maximum, and not before.