Analytical Testing Protocols for Food Contact Paperboard Extractives and Migration Metrics
Extractives and migration testing requires matching food simulants, extraction solvents, and analytical thresholds to specific regulatory contact conditions.
Sizing Agent Breakdown
Resin Hydrolysis
Surface sizing agent breakdown occurs when internal chemical bonds within cellulose reactive additives cleave under high alkaline exposure, reducing water resistance across high speed printing presses. Starch or alkyl ketene dimer emulsions lose their hydrophobic barrier when pH levels exceed baseline manufacturing tolerances during wet end processing. Hydrolyzed sizing molecules fail to anchor properly onto northern bleached softwood kraft fibres, leaving microscopic pathways open for liquid penetration during offset lithography.
Mill operators monitor Cobb values closely to detect early stages of sizing agent breakdown before finished paper reels ship to converting plants. Poor retention of alkyl ketene dimer molecules during sheet formation accelerates emulsion decay, ultimately causing feathering around halftone dots on coated art paper.
Emulsion Stability
Alkyl ketene dimer and alkenyl succinic anhydride dispersions rely on cationic starch protective colloids to prevent premature aggregation inside wet end piping networks. Shear forces generated by pressure screens can disrupt droplet integrity if cationic demand falls below optimal mill operating parameters. Coagulated sizing particles float freely through the headbox, depositing sticky agglomerates on wire mesh surfaces and causing web breaks on multi cylinder dryers.
Chemical suppliers adjust stabilizer ratios to withstand elevated stock temperatures without triggering phase separation before sheet consolidation occurs.
Press Defect
Liquid ingress during flexographic folding leads to delamination when degraded sizing agents fail to maintain inter fibre bonding strength. Converting lines running water based inks encounter blister formation if residual sizing degradation products react adversely with fountain solutions. Surface energy drops below forty dynes per centimetre, preventing uniform ink transfer across corrugated board liners.
Low sizing retention permits moisture migration into core fluting media, destroying compressive strength values specified for heavy shipping containers.