A Comparative CP/MAS 13C-NMR Study of the Supermolecular Structure of Polysaccharides in Sulphite and Kraft Pulps

Abstract

Summary The supermolecular structure of polysaccharides in unbleached sulphite pulps and kraft pulps was investigated by CP/MAS 13C-NMR (Cross Polarisation Magic Angle Carbon-13 Nuclear Magnetic Resonance) in combination with spectral fitting. The cellulose crystallinity was found to be higher in the kraft pulps than in the sulphite pulps. Acellulose Iα to cellulose Iβ conversion was observed during kraft pulping but not during sulphite pulping. The sulphite pulps exhibited smaller lateral fibril aggregate dimensions than the kraft pulps. The spectral behaviour of the hemicelluloses in the sulphite pulps was different from that in the kraft pulps. The general observation is that the supermolecular structure of the polysaccharides in the investigated sulphite pulps is very similar to the structure observed in wood.