Tailoring Pulp Cellulose with Electron Beam Irradiation: Effects of Lignin and Hemicellulose

Electron beam irradiation (EBI), which is applied industrially for sterilization of goods and cross-linking of synthetic polymers, can also be used for dissolving cellulose pulp production or whenever a reduction or an alignment of molecular mass of cellulose is needed. There is limited information about the differential performance of cellulose pulps produced by either kraft or sulfite pulping after EBI. In this study, special focus was placed on the ability of hemicellulose and lignin in kraft and sulfite pulps to protect cellulose from glycosidic chain scission and oxidation. In total, four hardwood paper and dissolving pulps with different hemicellulose and lignin contents were treated with EBI at an energy of 10 MeV and increasing doses of 0-100 kGy. Changes in the samples' molecular weight distribution and oxidation levels were analyzed by gel permeation chromatography and fluorescence labeling of carbonyl groups. Degradation efficiency was highest at low doses, and EBI showed homogeneous cellulose degradation. Analysis of carbohydrates leached from the pulp revealed preferential dissolution of polymeric hemicellulose fragments, correlating their presence to cellulose protection from chain scissions. Lignosulfonates were found to protect cellulose from both chain scission and oxidation but, controversially, kraft lignin was found to accelerate cellulose chain scission.