Open-Cell Aliphatic Polyurethane Foams with High Content of Polysaccharides: Structure, Degradation, and Ecotoxicity

Fully aliphatic (isocyanurate ring-based) polyester-ether polyurethane (PUR) foams have been developed, and the influence of starch and 2-hydroxyethyl cellulose (HEC) additives on their structure, properties, ecotoxicity, and (abiotic and biotic) degradation has been studied. These PUR foams designed as hydrophilic open-porous materials are predisposed to enzymatic hydrolysis with potential application as cellular carriers and an alternative nutrient source for activated sludge in wastewater treatment plants. In comparison to the neat (nonmodified) PUR foam, the PUR foams with incorporated starch and HEC modifiers exhibited a tougher character and a slightly increased open-cell content but on the other hand a significantly coarser cellular structure with much larger cell sizes and reduced water absorption. The progress of 6-week abiotic hydrolysis was characterized in detail, showing almost a complete decomposition of ester groups, a partial degradation of urethane linkages, and a fully intact isocyanurate ring. The extent of biodegradation by means of bacteria was similar for all tested PUR foams, while fungus biodegradation was more efficient in starch and HEC-modified PUR foams. The leachates from both starch- and HEC-modified foams exhibited somewhat higher ecotoxicity for higher organisms, here represented by Daphnia magna, due to higher contents of leached substances.

Automated summary

The study investigated the effects of starch and 2-hydroxyethyl cellulose additives on the structure, properties, ecotoxicity, and degradation of fully aliphatic polyester-ether polyurethane foams. The addition of starch and HEC resulted in tougher foam with slightly increased open-cell content but coarser cellular structure, larger cell sizes, and reduced water absorption. Biodegradation by bacteria was similar for all tested foams, while fungus biodegradation was more efficient in starch and HEC-modified foams, which also exhibited higher ecotoxicity for higher organisms.