FT-IR STUDY OF UV-IRRADIATED STONEGROUND WOOD PULP

The photo-induced colour reversion of handsheets of unbleached and bleached stoneground wood pulp was studied by FT-IR transmission spectroscopy. Changes in the chemical structure of thin handsheets were monitored quantitatively as a function of repeated exposures to UV irradiation at 320 nm followed by storage in the dark. A slight loss of carbohydrate structures was observed throughout the cycles, while a pronounced loss in lignin aromaticity was produced by the UV irradiation. The bleached samples, with a higher initial content of non-etherified groups, showed some evidence for preferential destruction of etherified groups throughout the irradiation cycles. A rapid initial decrease in alpha-carbonyl group content occurred for both bleached and unbleached samples; non-conjugated carbonyl group content increased with irradiation.