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Method for quantitative and molecular characterisation of adsorbed starch polysaccharides on a papermaking pulp by SEC-MALLS measurements and correlation with paper strength

: Ulbrich, M.; Radosta, S.; Vorwerg, W.


Starch = Stärke 61 (2009), Nr.6, S.311-320
ISSN: 0038-9056
Fraunhofer IAP ()

A laboratory-scale method for determining the molecularly dispersed amount of cationic starch adsorbed on a papermaking pulp was developed. The starch was molecularly dispersed by pressure cooking and was characterised by SEC-MALLS (Size Exclusion with Multi-Angle Laser Light Scattering) before and after the adsorption experiment. The adsorbed amount was calculated from the depletion of starch polymers in the starch-fibre suspension. The molecular composition of the adsorbed starch product was determined from the difference in the SEC chromatograms before and after adsorption. In addition, handsheets were formed to correlate starch adsorption on the pulp with the resulting paper strength. The value of the method was demonstrated using the example of a low DS cationic potato starch derivative. This sample from a slurry process was adsorbed to a significantly higher extent in virtually electrolyte-free deionised water (DW) than in water with a high electrolyte content (36 degrees German Hardness - 36 dGH). In DW, both amylopectin and amylose were adsorbed on the pulp, whereas in water of 36 dGH only the amylopectin-rich fraction was adsorbed. A correlation between starch adsorption as a function of water quality and the resulting paper strength was found. The amount and molecular composition of the adsorbed starch product influenced paper properties.