Fibre Fibrillation
Mechanical energy applied to chemical pulp alters individual cellulose structures through high shear forces. Kraft pulp refining transforms rigid, unbroken fibers into flexible ribbons with exposed fibrils, which increases the bonding surface area available during sheet formation. Stock preparation engineers manage this intensity through specific energy consumption metrics measured in kilowatt hours per ton.
Excessive energy input damages the structural integrity of the cellulose chain, reducing tear resistance while elevating tensile strength and density. Paper machines processing highly refined stock require precise drainage control on the wire section to prevent sheet formation defects.
Drainage Resistance
Water retention values rise proportionally as mechanical treatment exposes hydrophilic hydroxyl groups along the cellulose surface. Schopper Riegler numbers quantify this increasing drainage resistance by measuring the rate at which water separates from a dilute pulp suspension through a standard wire mesh. Refining intensity directly dictates how fast water leaves the web during pressing and drying stages on the paper machine.
Slow drainage limits machine speed and increases thermal energy demand in dryer sections, creating strict operational boundaries for the mill. Converting plants purchasing high freeness paperboard demand consistent drainage metrics to maintain dimensional stability during creasing and folding operations.
Tensile Development
Intermolecular bonding capacity expands dramatically when mechanical treatment removes the primary cell wall and exposes the secondary fibrillar layers. Tensile strength and burst strength climb steadily alongside refining degree, while opacity decreases due to the closer packing of translucent fibers within the dried sheet. Folding endurance improves as individual strands bend without fracturing under stress, providing the necessary durability for luxury folding cartons and corrugated packaging liners.
Printers specifying high smoothness grades rely on this mechanical conditioning to achieve uniform ink absorption and superior surface uniformity. Final paper performance depends entirely on balancing bonding strength against tearing resistance through controlled refining parameters.
