Viscoelastic Property Loss in Aqueous Coated Paperboard Converting
Moisture and thermal stress during converting plasticize aqueous latex coatings, reducing storage modulus and causing fold delamination unless web tension is optimized.
Score Line Bending Resistance
Folding Evaluation
Structural performance evaluation of folding boxboard focuses on the residual stiffness and mechanical behaviour of pre-scored hinge zones during package formation. In paperboard packaging testing, score line bending resistance measures the maximum bending force recorded when a prepared crease is folded through a ninety-degree angle over a standardized time interval. The resulting numerical value provides converters and packaging engineers with a direct measure of how effectively the die-cutting process delaminated the internal board structure without rupturing the continuous surface plies.
Machine Setup
Die-cutting platen tooling directly determines this bending property across both machine and cross grain directions. Correct score line bending resistance is achieved when the male creasing rule forces the paperboard into the female counter-channel, creating controlled internal shear delamination across the middle plies. The outer liner stretches in tension while the inner liner buckles inward to form a uniform, rounded bead that acts as an internal hinge.
Tool wear, incorrect female channel widths, or improper rule penetration increase bending resistance, which causes folded carton panels to bow outward under high internal tension. Regular testing across converting runs detects tooling misalignment early, allowing operators to adjust platen impression pressure or replace worn counter-dies before out-of-spec blanks reach high-speed filling plants.
Package Integrity
Cartons with consistently low, uniform score resistance fold square on automated erecting machinery and maintain exact dimensional tolerances during top-load stacking. Uncontrolled score resistance generates uneven panel deflection, misaligned tuck-in flaps, and broken glue joints during high-speed case packing and distribution.