Mechanically blown wall-projected tannin-based foams

• Published in: Industrial crops and products 2018-03, Vol.113, p.316-323
• Main Authors: Santiago-Medina, F.J., Delgado-Sánchez, C., Basso, M.C., Pizzi, A., Fierro, V., Celzard, A.
• Format: Article
• Language: English
• Subjects: Engineering Sciences; Foam concentrate; Foams; Mechanical foaming; Quebracho; Tannin; Thermal conductivity
• ISSN: 0926-6690; 1872-633X
• DOI: 10.1016/j.indcrop.2018.01.049

•Tannin based foams prepared by mechanical expansion using surfactants as blowing agents.•More controlled expansion and curing steps, avoiding problems of contraction.•First steps to achieve the development of an ecofriendly projected foam. Condensed flavonoid tannin-based foams from quebracho tannin extract have been developed using a new method of expansion based on fire-fighting or tunneling foams, where a foam concentrate forms a stable liquid foam. This new mechanical method of expansion allows obtaining a solid porous material after curing and hardening at room temperature, through a liquid foam formed by a tannin resin and an aqueous solution of surfactant. The stability of the as-obtained liquid foam and the influence of the amount of catalyst are reported. The use of this new approach for preparing tannin-based rigid foams avoids the problem of shrinkage presented by many other formulations where physical or chemical foaming is employed. Non-ionic surfactants have also been used in the formulation to obtain smaller cells and improve the structure of the new material. Bulk density (0.069–0.080 g/cm3), mechanical (compressive strength of 0.034–0.13 MPa) and thermal (0.045–0.047 W m−1 K−1) properties and morphological appearance of the foams have been characterised and reported.