EFFECTS OF ENZYMATIC REMOVAL OF XYLAN AND GLUCOMANNAN ON THE PORE-SIZE DISTRIBUTION OF KRAFT FIBERS

The effects of enzymatic removal of xylan and glucomannan from pine an d birch kraft pulps on the pore size distribution and median pore widt h of the pulp fibres were determined by modified solute exclusion and H-1 NMR techniques. With the NMR method, clearly higher median pore si zes of the kraft fibres were obtained compared with the solute exclusi on method. However, the effects of enzymatic treatments on pore size d istributions and median pore widths of fibres were detected by both te chniques. An increase in the pore width of both pine and birch kraft f ibres was observed even after a limited xylanase treatment. The NMR te chnique appeared to be more suitable than the solute exclusion method for determination of the further increase of the median pore width and the widening of the pore size distribution of fibres by a more extens ive xylanase treatment. Both techniques revealed an increase of the me dian pore width of fibres caused by the extensive removal of pine kraf t pulp glucomannan. Despite their basic differences and specific limit ations, both the NMR and solute exclusion techniques showed the enzyma tic effects on the porosity of pulp fibres.