Modeling Hygral Stress Profiles and Edge Waving in High-Bulk Recycled Cartonboard Skids
Modeling transient moisture gradients and hygral stress in high-bulk recycled cartonboard skids establishes barrier wrap limits to prevent press edge waving
Z-Direction Diffusivity
Vertical Permeability
Internal void structure regulates how liquids move through the thickness of a paper sheet, an action specifically identified as z-direction diffusivity. This measurement quantifies the resistance of a fibre network against the movement of a fluid perpendicular to the surface plane. High values indicate a porous network that allows rapid penetration of aqueous coatings or printing inks.
Manufacturers rely on this data to control the depth of penetration for functional barriers, ensuring that the additive remains at the surface rather than migrating into the bulk of the stock.
Manufacturing Calibration
Production mills adjust the refining intensity and wet end chemistry to manage the alignment of cellulose fibres and the resultant density of the sheet. Dense arrangements limit fluid passage, whereas bulkier structures accelerate the flow rate through the middle layers. Conversion processes such as curtain coating require precise control over these pathways to prevent excessive absorption that would otherwise drain the surface treatment away.
Excessive porosity leads to uneven drying and potential strike through during the deposition of pigments or adhesive layers.
Performance Constraint
Material failure occurs when the internal pore network lacks sufficient resistance to maintain the structural integrity of the substrate under fluid pressure. Laminating operations depend upon this resistance to avoid the over penetration of bonding agents which causes dry spots or paper curling. Consistent control of this movement ensures that coating weights remain accurate across the entire width of the web.
Proper management of these internal gaps stabilizes the interaction between the substrate and liquid chemicals, governing the final physical characteristics of the processed material.