Effects of chain extender in biodegradable polyurethane foams.

Molded flexible polyurethane (PU) foams were synthesized from a starch/petroleum based polyol, 2,4/2,6-toluene diisocyanate (TDI-80), using a one shot method with water as the blowing agent. The effects of chain extender type [starch (S series), diethanolamine (DEA, D series), glycerol (G series)] and content (0, 2, 5, 10 pphr) were extensively studied. The rate of foam formation, density, compression strength, glass transition temperature (T_g) and rubbery modulus of the foam increased with the addition and increasing content of extender. At the same extender content, DEA showed the highest of these properties, while starch showed the lowest. The rate of biodegradation in a buffer solution decreased with the addition of DEA and glycerol, due to the increased crosslinking density and hard segment content, but increased with starch, owing to its biodegradability. [ABSTRACT FROM AUTHOR]