Surfactant Diffusion Rate Impact on Air Entrainment Thresholds in Curtain Coaters
Surfactant diffusion kinetics govern dynamic surface tension within millisecond curtain residence times, dictating high-speed air entrainment speed thresholds.
Cobb Absorptiveness
Liquid Penetration
Standardized gravimetric metrics evaluate the mass of water absorbed by a defined paper or board surface over a set exposure duration. Packaging materials destined for refrigerated boxes or liquid cartons must restrict aqueous liquid penetration to maintain structural rigidity under humid storage conditions. Determination of cobb absorptiveness follows ISO 535 procedures, measuring grams of water retained per square metre during sixty-second or two-hundred-second exposure periods.
High absorption values signal inadequate internal or surface sizing, exposing paperboard packages to moisture softening and stacking collapse.
Test Methodology
Testing requires clamping a dry paper specimen beneath a metal ring, filling the cylinder with distilled water, and timing the liquid contact precisely. At the end of the test window, excess surface water is blotted away between standardized absorbent sheets using a standardized steel roller. The weight gained by the conditioned specimen determines the final metric value.
Inconsistent rolling pressure or delayed blotting creates artificial variance in reported test results across testing laboratories.
Sizing Control
Alkyl ketene dimer and alkenyl succinic anhydride sizing agents reduce water penetration by orienting hydrophobic carbon chains away from cellulose fibres. Hardened surface starch coatings further seal capillary pores, lowering overall liquid uptake across corrugated containerboard grades.