Interply Delamination Energy Thresholds during High Speed Converting of Recycled Paperboard Grades
Matching dynamic Scott Bond energy above 120 J/m² prevents high-speed folder-gluer delamination and reduces net carton cost through lower line scrap.
Spray Starch
Ply Bonding
Inter-ply adhesive application techniques deposit uncooked starch granules directly onto wet paperboard webs during multi-cylinder sheet formation. Spray starch enhances ply bond strength, burst index and stiffness in multi-ply containerboard and folding boxboard. The chemical treatment binds individual fiber plies together as the web passes through dryer sections where heat gelatinizes the starch granules.
It governs internal z-directional tensile strength and delamination resistance during high-speed scoring. The application stops applying on single-ply paper grades or where wet-end native starch wet-end dosages provide adequate structural cohesion.
Thermal Gelatinization
Precise nozzle positioning delivers a uniform spray pattern across the moving web prior to the press section. Uncooked starch particles remain inert until moisture and thermal energy in the cylinder dryers trigger swelling and gelatinization. Spray starch flows around wet fibers at inter-ply interfaces, creating strong adhesive bonds upon drying.
Insufficient dryer temperature leaves ungelatinized starch granules, which fail to develop mechanical bonding and act as internal flaws. Excess spray mist creates nozzle clogging, leading to streaking, uneven ply bond across the machine width and localized board delamination during converting.
Application Boundary
High moisture levels at the spray location wash away starch particles before web consolidation occurs. Spray starch application loses effectiveness if web dryness prior to spraying exceeds thirty percent.