The influence of dextran molecular weight on the dry strength of dextran-impregnated paper

Bleached softwood kraft pulp handsheets were impregnated with aqueous dextran solutions, which were employed as mode! dry strength polyners. The dry tensile strength of the treated sheets increased linearly with the dextran content. Greater strength improvements were obtained with the higher molecular weight dextrans, although the mechanical properties of pure dextran films were not very molecular dependent. Comparison with earlier results revealed that impregnation gave approximately the same strength improvements, as did wet-end addition when compared at the same dextran content Fluorescent-labeled dextran was used to observe directly capillary forces carrying the dextran to the junction of crossed glass or cotton fibers, gluing them together - presumably the same mechanism occurs when daxtran impregnated paper is dried. Application: This study looks at the role of the dry strength additives.