Paperboard Repulpability Assessment under Standard Laboratory Disintegration Conditions
Standard laboratory disintegration assesses paperboard repulpability by measuring defibering rates, fiber yield, and screen reject fractions under fixed shear.
Fines Generation
Fiber Degradation
Microscopic cellulose fragments and cell wall debris accumulate in paper pulp slurries during mechanical refining or repeated recycling. The fines generation measures the production of these tiny elements that are small enough to pass through a standard screen or round holes of seventy-six micrometres. These particles change the drainage properties of the pulp and affect the strength of the final paper sheet.
Papermakers monitor this accumulation to keep a balance between sheet density and water removal rates on the wire.
Refining Action
Mechanical action in refiners peels away the outer layers of cellulose fibers to increase their surface area for hydrogen bonding. During this treatment, the fines generation occurs as a byproduct of the intense shear and compression forces applied to the wet fibers. When fibers are bruised, small fibrils break off entirely, forming suspended debris that floats in the water.
High quantities of these small particles fill the voids between larger fibers, which increases the density of the sheet but slows down drainage on the forming table. In high-speed paper machines, excessive fines reduce the vacuum efficiency and can cause wet-end breaks.
Dewatering Resistance
Slow drainage increases the drying energy required to produce a ton of paper board. When the fines generation is kept within tight limits, the pulp drains quickly and allows higher machine speeds.