Morphology-induced differences in adsorption behaviors and strength enhancement performance for fiber networks between quaternized amylose and amylopectin

Cationic starch is the most widely used paper strength additive for papermaking wet end applications. However, it remains unclear how differently quaternized amylose (QAM) and amylopectin (QAP) are adsorbed on the fiber surface and their relative contribution to the inter-fiber bonding of papers. Herein, separated amylose and amylopectin were quaternized with different degrees of substitution (DS). After that, the adsorption behaviors of QAM and QAP on the fiber surface, the viscoelastic properties of the adlayers and their strength enhancement to fiber networks were comparatively characterized. Based on the results, the morphology visualizations of the starch structure displayed a strong impact on the adsorbed structural distributions of QAM and QAP. QAM adlayer with a helical linear or slightly branched structure was thin and rigid, while the QAP adlayer with a highly branched structure was thick and soft. In addition, the DS, pH and ionic strength had some impacts on the adsorption layer as well. Regarding the paper strength enhancement, the DS of QAM correlated positively to the paper strength, whereas the DS of QAP correlated inversely. The results provide a deep understanding of the impacts of starch morphology on performance and offer us some practical guidelines in starch selection.

Automated summary

Cationic starch is commonly used as a paper strength additive in papermaking wet end applications. The study investigates the adsorption behaviors and strength enhancement of quaternized amylose (QAM) and amylopectin (QAP) on fiber surfaces. The results reveal that the adsorption layer thickness and structure of QAM and QAP are influenced by starch morphology, degree of substitution, pH, and ionic strength. Furthermore, the degree of substitution of QAM positively correlates with paper strength, while the degree of substitution of QAP negatively correlates with paper strength. These findings provide insights into the impact of starch morphology on performance and offer practical guidelines for starch selection.