Eucalyptus Fiber Morphology and Inter Fibre Hydrogen Bond Density
Eucalyptus fiber collapse and hydrogen bond density dictate sheet tensile strength, bulk retention, and landed sheet cost in commercial packaging grades.
Runkel Ratio
Structural Proportion
Cellulose morphology governs how paper sheets resist compression and bending forces during conversion. The runkel ratio calculates the mathematical relationship between cell wall thickness and lumen diameter within wood fibres. Mechanical pulping and chemical digestion processes alter this internal proportion directly to influence sheet density and tear resistance.
High wall fractions yield stiffer fibres that resist collapse during pressing, creating voluminous packaging grades with high bending stiffness. Low wall fractions allow fibres to flatten into ribbons during drying, maximizing bonding area to produce dense greaseproof papers and glassine.
Milling Impact
Refining equipment applies mechanical shear that modifies fibre dimensions before web formation. Refining alters the effective cross section by bruising and partially collapsing the outer layers of the cell wall. Higher refining energy reduces drainage rates on the paper machine wire as disrupted fibres retain water internally.
Board mills monitor this structural metric to predict how base stock will behave under high speed converting lines and corrugating rolls.
Conversion Performance
Folding carton stiffness depends heavily on the initial cell geometry established in the pulper. Thicker cell walls maintain internal voids within the board matrix, providing structural rigidity without increasing basis weight. Converters adjust scoring depth and crease pressure based on how much the substrate resists deformation during box erection.
Final packaging performance relies on balancing fibre coarseness against surface smoothness to ensure clean die cutting and reliable glue line adhesion.