Grafting of Radiation-Peroxidized Lignin

Abstract

Lignin is subject to easy radiation-peroxidation. In the case of pine hydrochloric acid lignin, irradiation of 1.92 Megarads of γ-ray in air gave rise to 3×1019 peroxide per gram of lignin. When the peroxidized lignin was allowed to stand in air, the peroxide contents diminished in 25 days to 40%, which was, thereafter, invariable for 250 days. When styrene or methyl methacrylate was used as monomer in the grafting there was reaction of 36 parts of styrene or of 39 parts of methyl methacrylate to 100 parts of lignin, but it was not the case with ligninsulfonic acid. Up to 1.92 Megarads of dose amount applied, the peroxide concentration in lignin increased proportionally with the radiation period, but the grafting ratio indicated maximum value at the point of a peroxide content of 1.89×1019 per gram of lignin. When polystyrene branches propagated up to Pn of 100, the corresponding grafting ratio reached to 35 in the radiation-peroxidation method and 200 in the case of direct radiation method respectively. This means that. in the case of radiation-peroxidation method, the number of active centers for grafting is one-sixth compared with those which appeared in the direct radiation grafting. From the so far known structure of lignin and the experimental results obtained here, it is to be concluded that the peroxides produced in the lignin molecules by pre-irradiation were mostly hydroperoxide arising from C-H scission at tertiary carbon, and less in diperoxide.