Fibre Modification
Mechanical treatment applied to pulp suspensions at decreased solids concentrations modifies internal and external fibrillation without excessive length reduction. Low consistency refining forces stock through a narrow gap between rotating and stationary grooved metal bars, generating high shear forces that swell individual cellulose elements. Primary cell walls peel away during this passage, exposing hydrophilic fibrils that increase bonding sites across the finished sheet.
Specific edge load calculations dictate the applied energy intensity, balancing tear strength retention against tensile development for precise structural control.
Drainage Resistance
Stock preparation adjustments alter water retention values and Schopper Riegler numbers, directly impacting machine speeds on Fourdrinier formers. Dense networks restrict interstitial water flow during initial dewatering stages, requiring increased vacuum box capacity and higher press nip pressures to reach target dry weights. Fines generation during intense bar contact plugs voids within the web, slowing drainage rates and shifting drying energy demands toward cylinder sections.
Controlled intensity prevents excessive beating degree escalation, maintaining adequate permeability for rapid air removal through felts.
Surface Uniformity
Interfiber bonding improvements eliminate microscopic voids, producing smooth substrates capable of accepting uniform ink coverage during offset or gravure printing. Higher apparent density reduces ink absorption variation, preventing print mottle and maintaining sharp dot reproduction across coated and uncoated grades. Caliper losses accompanying elevated densification require adjustments in calendering loads to preserve bulk while meeting specific stiffness requirements for folding carton applications.
Final sheet smoothness determines varnish holdout and gloss development, linking mechanical pulp treatment directly to visual print quality.
