Optimizing Multi-Ply Layering for Enhanced Post-Consumer Containerboard Performance
Multi-ply layering of post-consumer containerboard optimizes flexural stiffness and crush resistance by concentrating long fibers in outer faces.
Dry Strength Resin
Chemical Binding
Chemical additives introduced to the pulp slurry before sheet formation increase the mechanical resistance of the dried paper. A dry strength resin, typically a synthetic polymer like polyacrylamide or a modified natural polymer like cationic starch, functions by creating additional bonds between the cellulose fibres. These additives supplement the natural hydrogen bonds that form as the water evaporates from the sheet during drying.
Their application is restricted by the chemical saturation point of the fibres, beyond which excess polymer fails to adhere and remains in the process water.
Retention Mechanism
Effective performance of the polymer depends on its charge relative to the negatively charged wood fibres in the stock. When a cationic dry strength resin is added to the slurry, it associates with the anionic sites on the cellulose surfaces, ensuring it is retained in the forming paper web. If the wet-end chemistry is unbalanced, the polymer may remain in the water, leading to a buildup of organic materials that disrupts the runnability of the paper machine.
Packaging Performance
Boxboard and corrugated packaging grades require high resistance to compression and bursting when stored in humid conditions. Incorporating a dry strength resin allows manufacturers to use higher percentages of recycled fibres without sacrificing the structural performance of the boxes. This addition maintains the rigidity of the carton during transport and handling.