COMPRESSIVE PROPERTIES AND BIODEGRADABILITIES OF POLYURETHANE FOAMS DERIVED FROM CONDENSED TANNIN

Polyurethane (PU) foams were prepared without the use of solvents from a three-component system consisting of diisocyanate (DI), polyester ( PES), and non-modified wattle tannin (WT). PU foams having different W T contents up to 25% and densities from 0.10 to 0.20 g/cm3 were prepar ed by controlling the addition of the catalyst, the isocyanate/hydroxy l group ratio, and the water content. No crosslinking agents were nece ssary. The compressive strength and elasticity of the PU foams increas ed with increasing WT contents and NCO/OH ratios. These facts indicate that WT plays the role of a crosslinking agent and acts as hard segme nts in the PU foam structure. The PU foams derived from WT seem to be potentially biodegradable because a PU foam containing 25% WT was degr aded slowly by some wood-rotting fungi, Whereas a PU foam without WT w as stable to these fungi.