STUDIES OF CELLULOSE SURFACES BY TITRATION AND ESCA

The surface properties of unbleached kraft pulp fibers of varying lign in content prepared by digestion with different amounts of excess alka li have been investigated using polyelectrolyte titration, potentiomet ric titration and ESCA. The surfaces contain two different acidic grou ps that dissociate completely above pH 7.5, one with pK approximate to 3.6 and one with pK approximate to 5.7. The amount of the latter grou p correlates directly with the amount of lignin in the pulp. The ESCA analysis indicates that the relative amount of carboxylic groups and a lkyl carbon in the surface decreases as the lignin content decreases a nd also that material with high alkyl carbon content is enriched in th e outermost surface of the cellulose. Thus, a combination of ESCA anal ysis and high-precision titrations is able to yield a very detailed pi cture of the effect of digestion conditions on surface properties of c ellulose fibers of direct relevance to paper properties.