Abstract
In the present study, the surface properties of cellulosic fibres have been systematically varied and the dispersive and acid-base properties have been determined by inverse gas chromatography (IGC) at infinite dilution.
Bleached kraft pulp fibres were carboxy methylated to different degrees. The results from the IGC measurements on the carboxymethylated fibres showed a linear relationship between the interaction energy with a basic probe (acidic properties) and the carboxylic acid group content. The extrapolation to zero degree of substitution ofcarboxylic acid groups indicates that,even in the absence of carboxylic groups, the fibres have acidic properties. The hydroxyl groups on the fibres obviously also contribute to the acidic properties. The interaction energy with an acidic probe (basic properties) was relatively constant with increasing carboxylic acid group content. An increase in the degree of carboxymethylation also seemed to slightly increase the dispersive part of the surface free energy. This could be a consequence of an increase in electron density, a more compact structure after drying the carboxymethylated fibres or removal of low molecular weight impurities. The dispersive as well as the acid-base properties are approximately the same for pulps in both their proton and sodium forms.
The carboxymethylated fibres were peeled after the modification. The carboxylic group contents of the fibres and of the removed outer layers were determined by conductometric titration. The results showed that the carboxymethylation procedure is somewhat more effective in the outer layers of the fibres.
IGC results for the peeled fibres pointed in the same direction. Diethylaminoethyl{DEAF}cellulose, which has a basic functional group was also characterised. The IGC results showed that the DEAE cellulose interacts more strongly with the acidic probe than the reference cellulose material
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