Effect of saturation adsorption of paper strength additives on the performance of paper

The use of paper dry strength additives is oneof the methods for producing packaging boards with alower grammage while maintaining mechanical properties.In the present work, papers were formed using dissolvinggrade kraft fibres, kraft fibres and carboxymethylatedcellulose (CMC) modified kraft fibres (C-kraft fibres),with either cationic starch (CS), anionic polyacrylamide(APAM) or anionic polyelectrolyte complexes (PECs). Fibresand sheets were characterized to evaluate how the saturationadsorption of the different strength additives influencesthe properties of the treated fibres and the finalhandsheets. The tensile index of papers made from C-kraftfibres was the highest due to the highest adsorption capacityof strength additives. Moreover, the strength additivesincreased the tensile index by 33–84 %, while z-directional tensile strength was increased dramatically by 46–139 %.Bending stiffness was improved by 2.6–25 %, and the combination of CS and APAM or PECs resulted in a significantimprovement in bending stiffness compared to the addition of CS alone. Importantly, the strength improvement did not sacrifice the density significantly. In summary, theknowledge gained from the current study expands the understanding of strength additives and their relationship with fibres of different surface charge and the overall paper properties.QC 20221227