Studies on photostability of butyrylated, milled wood lignin using spectroscopic analyses

Photo-stabilisation of butyrylated milled wood lignin (MWL) was investigated in this study. Chemical changes were confirmed by NMR and FT-IR spectra after butyrylation. Improvements in the photostability of MWL by butyrylation were evaluated by spectral analyses including ESR, FT-IR and UV-VIS spectra. From ESR analyses, butyrylation reduces the amount of phenoxyl free radicals of MWL after UV irradiation, which results in inhibiting the photo-oxidation of lignin followed by a significant decrease in the formation of colored chromophores. The carbonyl, carboxyl and quinonoid structures were less detected in the butyrylated MWL after UV irradiation than those of untreated MWL, and the content of degraded water-soluble materials from the photo-degradation of MWL was also reduced upon butyrylation.