Resin Sizing
Dimensional stability on corrugated containers depends heavily upon internal sizing procedures governed by TAPPI T 625. Cellulose fibres absorb moisture readily from ambient humidity during storage unless hydrophobic compounds block the microscopic capillaries within the sheet structure. Rosin soap combined with aluminium sulphate precipitates aluminum salts onto the fibre surfaces during wet end processing to establish baseline water resistance.
Converted boxes maintain stack strength in high humidity storage conditions only when this chemical treatment prevents moisture migration into the corrugated medium.
Extraction Method
Laboratory evaluation of sizing efficiency relies upon solvent extraction procedures defined within TAPPI T 625 to quantify non-fibrous residues accurately. Chloroform or other specified organic solvents dissolve resinous materials from ground paper samples through Soxhlet extraction apparatus during extended boiling cycles. Gravimetric measurement of the dried extract establishes the exact mass fraction of sizing agents retained within the paper matrix after drying.
Analytical precision requires strict adherence to boiling durations and solvent purity because residual moisture interferes with the final mass determination.
Performance Limit
Corrugated linerboard manufacturers utilize TAPPI T 625 metrics to verify that sizing levels do not interfere with subsequent wet strength resin applications or neutral sizing chemistries. Excessive sizing agent concentration reduces water-based adhesive penetration on the corrugator single facer, leading to weak bond formation and eventual flute delamination. Production lines adjust alum addition rates dynamically when extraction data reveals variation in sizing retention across different basis weight runs.
Final box compression performance drops significantly if sizing levels exceed the upper operational threshold established by standard test methods.
