Tannin-based carbon foams

An easily-prepared self-blowing system based on low-cost precursors, mainly tannin and furfuryl alcohol, was pyrolysed at 900 degrees C. Extremely low-density glass-like carbon foam was obtained, with very high porosity (96.4%, of which 94% is open) and low surface area (below 1 m(2) g(-1)). The material presents slightly anisotropic properties. The linear cell density is 100 and 190 ppi along two orthogonal directions, and the major physical properties were examined according to these same directions: electrical and thermal conductivities, mechanical strength and elastic modulus, coefficient of thermal expansion, permeability and fire resistance. Since most of these properties compare very correctly with available data from the literature, such a cheap material like the one reported here can compete with commercial vitreous carbon foams, which are all produced from more expensive, non-renewable, resources. (C) 2009 Elsevier Ltd. All rights reserved.