Gamma-ray induced chromophore modification of softwood thermomechanical pulp
1993
Robert, S. | Daneault, C. | Lepine, F. | Viel, C. | Rousseau, D.
This study focuses on the bleaching of a softwood (black spruce, balsam fir) thermomechanical pulp with gamma irradiation. The effects of sodium borohydride, oxygen, hydrogen peroxide, nitrous oxide and water along with gamma ray irradiation of the pulps were studied. The optimal dose and dose rate, the influence of radical scavengers such as oxygen on the bleaching effect of gamma ray irradiation of pulps as well as the various degrees of bleaching of these pulps were measured. Evidence is presented to relate this bleaching to the generation of reactive species upon gamma ray irradiation of water. These species possess a behavior similar to hydrogen peroxide toward lignin, but are detrimental to cellulose, particularly to the micro fibrils. The main change is to the physical properties and scattering coefficient of the fibers. It is possible to relate the influence of the dose rate to the disappearance of chromophores on lignin, but the effect is very small.
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