Mechanical Greaseproof Paper Grade Selection for Bakeries and Fast Food Packaging
Optimize mechanical greaseproof paper selection by specifying 80-88 SR refining and 15000+ s Gurley porosity to secure non-PFAS grease resistance.
Capillary Flow Dynamics
Liquid Transport
Liquid penetration through the interconnected pore network of a paper web dictates the rate of ink vehicle sorption during high-speed offset or flexographic printing operations. Analysis of capillary flow dynamics determines how fast water or solvents move into the fiber matrix before surface drying occurs. Wetting mechanics follow Lucas-Washburn relationships where fluid transport depends on pore radius, liquid viscosity, and surface energy.
Microscopic capillary channels draw fluid away from the surface layer into the sheet interior. Rapid absorption stabilizes ink pigments, which prevents dot gain and ink smearing on printing presses.
Pore Architecture
Pore size distribution within the fiber network controls the balance between capillary suction force and liquid flow volume. Small pores generate high capillary pressures that pull liquid vehicles deep into the sheet structure. Large void spaces allow high volumetric flow rates but exert weaker capillary attraction.
Coating pigments such as calcium carbonate or kaolin clay modify surface pore geometry, creating uniform pore networks that regulate ink solvent absorption rates. Fiber refining increases internal sheet density, which reduces mean pore radius and slows down fluid movement through the web. Chemical sizing agents alter the contact angle between liquid droplets and cell wall polymers, turning hydrophobic surfaces into water-resistant structures that delay liquid entry.
Converting processes measure fluid absorption rates using liquid permeability equipment and ultrasonic penetration analyzers. When pore structure remains inconsistent across the paper machine width, ink vehicle separation varies, causing print density fluctuations and uneven gloss appearance across the printed sheet.
Absorption Boundary
Excessive capillary uptake causes ink vehicle depletion at the surface layer, leaving pigments inadequately bound to fiber walls. Insufficient fluid transport leaves liquid ink standing on the sheet surface, resulting in offset ink transfer inside press delivery piles. Printing press speed sets the time window available for liquid absorption before mechanical contact occurs at downstream nip stations.