Structural Network
Interlocking plant polymers formed during wet web consolidation establish the physical framework of paper and board substrates. A cellulose fiber matrix consists of refined wood fibers held together by hydrogen bonds and mechanical entanglement. Fiber orientation during wet laying dictates anisotropic tensile properties in machine and cross directions.
Pore distribution within this network controls fluid capillary action and varnish holdout during offset printing.
Mechanical Cohesion
Refining mechanically disrupts the outer primary wall of hardwood and softwood fibers to expose hydroxyl groups. These exposed groups form strong intermolecular hydrogen bonds as water evaporates across the dryer section. Compaction under wet press nips increases contact area between individual fiber surfaces.
When refining is carried too far, fiber shortening reduces tear resistance while increasing sheet density beyond ideal packaging specifications. Internal bond strength directly determines how well a folding boxboard resists delamination during heavy creasing and high-speed scoring operations. Inadequate bonding allows plies to separate during convertor bending steps.
Drainage Behaviour
Freeness values reflect the speed at which water departs from the slurry on the forming fabric. High wall swelling slows dewatering, requiring longer vacuum suction zones. Forming fabrics dictate initial fiber orientation before vacuum pulses lock the wet web structure in place.
