Self-Blowing Non-Isocyanate Polyurethane Foams Based on Hydrolysable Tannins

Abstract

Non-isocyanate polyurethane (NIPU) foams using a hydrolysable tannin, also vulgarly called tannic acid, namely here commercial chestnut wood tannin extract was prepared. Compression strength did not appear to depend on the foam apparent density while the formulation composition of the NIPU foams has been shown to be more determinant. These NIPU foams appeared to be self-extinguishing once the high temperature flame is removed. The ignition time gave encouraging results but for improved fire resistance the foams may need some fire-retardant addition. FTIR spectrometry showed the formation of non-isocyanate urethane linkages. Thermogravimetric analysis indicated a good thermal resistance of these foams, with thermal degradation following four phases. First in the interval 25°C–120°C range, mainly evaporation of water occurs with a maximal loss of 10% weight. In the 150°C–450°C temperature range foams mass loss is of almost 70%. In particular in the 125°C–275°C range occurs the degradation of some small molecular weight substances. In the 500°C–790°C temperature range the foams do not present any further large degradation.