Optimization of Amylose to Amylopectin Ratio and Degree of Substitution in Quaternized Starch as a Tool to Improve Paper Strength

Cationic starch serves as a prevalent wet-end additive in the papermaking industry. Yet, the definitive effects of the ratio between the two principal components-amylose (AM) and amylopectin (AP)-and the degree of substitution (DS) on the mechanical strength enhancement of paper sheets remain incompletely understood. This study synthesizes a series of quaternized amylose (QAM) and quaternized amylopectin (QAP) with varying DS levels and blended these derivatives in diverse ratios. Subsequently, these mixtures are integrated into pulp suspensions to ascertain the DS and the AM-to-AP ratio that optimize paper strength. These results indicate that a QAM-to-QAP blend with a DS of 0.08 at a ratio of 2:8 yielded the most pronounced improvement in paper mechanical properties. This precise formulation significantly enhances tensile, burst, and tear strength indices, increasing by approximately 55.0%, 44.4%, and 78.4%, respectively, under the most favorable conditions and with an additive dosage of 1 wt.%. This investigation provides substantive and actionable knowledge for selecting starch additives in the wet-end of papermaking, which can significantly augment the efficiency and efficacy of paper manufacturing processes.