EffEct of ionic form on fibrillation and thE dEvElopmEnt of thE fibrE nEtwork strEngth during thE rEfining of thE kraft pulps

Abstract

abstract the refining of unbleached kraft pulps in their na + -form has shown energy saving potential. in this study, the fibre network strength of unrefined and laboratory refined samples of an unbleached neverdried kraft pulp in different ionic forms was studied. the external fibrillation and the fibre flexibility were also studied. the objective was to investigate whether the improved refinability of fibres in the na + -form could be related to the floc network strength or to fibrillation characteristics. the results showed that the rheological properties may not explain the improved refinability of fibres in the na + -form, since fibres showed similar rheological properties regardless of their ionic form. measurements using the mms (pulp measuring system) showed that fibres refined in the na + -form have a larger amount of external fibrillation, and microscopic investigation confirmed that the characteristics of the fibrils are different for fibres refined in the na + -form from those of fibres refined in the h + -or ca 2+ -forms. the observed differences in fibrillation and improved refinability may be explained by the co-operation of electrostatic interactions of the fibre wall and the mechanical forces applied during refining