Modification of renewable resources—lignin—by three chemical methods and its applications to polyurethane foams

To improve the economic viability of polymer from renewable resources, a value‐added lignin polymer is increasingly important. The lignin was successfully modified by three chemical methods: hydroxymethylation, epoxidation, and phenolation. Through these methods, the percentage of impurity had decreased, and the number of phenolic hydroxyl groups of lignin had dramatically increased, particularly by phenolation, reaching 9.41%, nearly three times higher than that in the unmodified one. Meanwhile, we added different amounts of modified lignin into polyurethane foams, and the results showed that 1 wt% modified lignin could not only increase the decomposition temperature of the foam material but also remarkably improve its mechanical properties. The optimum reaction time was 4 hr, and the reaction temperature was 80°C for blends. Copyright © 2014 John Wiley & Sons, Ltd.