Liquefaction of Lignin Using Chemical Decomposition and Its Application to Polyurethane Foam

To utilize the chemical application of lignin (LN), a decomposition reaction was carried out to cleave chemical bonds. Indeed, a liquefaction process is essential for the chemical use of lignin to achieve a uniform reaction and maximize the chemical utility of lignin. To this end, hydroxyl radicals were adopted as a powerful oxidation agent, and FT-IR results confirmed the cleavage of the ether linkages. Additionally, the water solubility of LN significantly increased after decomposition, and dissolution levels up to 0.5 g·mL–1 were obtained. Using these high solubility properties in water, NMR and DLS analyses were performed. In particular, an average particle diameter of 300 ± 240 nm was found, corresponding to the size of polydisperse l-LN. By controlling size uniformity and using high water-solubility levels, polyurethane foams were manufactured using l-LN.