Effect of composition and processing parameters on the characteristics of tannin-based rigid foams. Part II: Physical properties

The present work is the continuation of the previous one published in the same issue of this journal, but now focuses on some selected physical properties of tannin-based rigid foams and derived glasslike carbon foams. Such materials are new, lightweight, cellular solids, prepared from 95% natural precursors: bark extracts and furfuryl alcohol, as detailed in the companion paper. After a few structural characteristics are briefly recalled, physical properties like compressive strength, permeability to fluids, solvent absorption, and electrical conductivity are measured, discussed and modelled. The effects of changing a few experimental parameters that have been varied in the synthesis of the foam: amounts of blowing agent, strengthener and nanofillers, shape of the moulds and restricted foaming are discussed in relation with the pore structure observed in the companion paper. Slightly anisotropic properties are evidenced, in agreement with the orientation of the cells, as expected for foams grown vertically in cylindrical moulds.