Effect of Cross-Linking Fiber Joints on the Tensile and Fracture Behavior of Paper

The tensile and fracture properties of cross-linked paper were investigated at low and high relative humidity by cross-linking the joints formed between fibers. Cationic acetal dextran served as a model cross-linking agent, as it can be prepared to adsorb specifically to the fiber surface. Thus, cross-linking occurs only in the joints between fibers. The kinetics of hydrolysis was investigated to optimize the stock preparation, such that the resulting aldehyde groups react as the paper is dried. The effect of the cross-link density on the tensile and fracture properties was studied by varying the amount of acetal groups adsorbed to the pulp fibers. At low humidity, cross-linking improved the tensile and fracture properties of paper, although lower cross-link densities yielded better properties. Cross-linking was not effective at high relative humidty, as the tensile strength and stiffness were not improved. However, the fracture properties were significantly improved.