Ultrasonic Wave Attenuation Basics for Paperboard Creasing Quality
Non-destructive ultrasonic wave attenuation evaluates paperboard crease quality by measuring acoustic energy loss caused by internal shear delamination.
ISO 5628 Bending Stiffness
Standard Specification
Standardized mechanical test protocols establish consistent procedures for measuring the resistance of paper and board substrates to bending forces applied within their elastic deformation limits. Under international testing frameworks, iso 5628 bending stiffness defines two-point, three-point, and four-point loading methods to quantify the bending moment per unit width required to deflect a vertically or horizontally clamped test piece through a specified angle. The standard governs quality assurance for packaging grades ranging from lightweight folding boxboards to heavyweight solid bleached boards.
Measurement Principle
The test operates within the linear elastic regime of the paperboard, ensuring that fibre deformation remains fully reversible without internal delamination or creasing. When executing the two-point method outlined in iso 5628 bending stiffness, a rigid clamp secures the bottom edge of a rectangular specimen while a moving load sensor contacts the opposite free edge, deflecting it across a standard angle of five or fifteen degrees over a fixed span length. The resulting bending moment, expressed in millinewton metres or newtons, reflects both the tensile modulus of the outer liners and the compressive modulus of the middle plies.
Multi-ply cartonboard construction relies on this mechanical principle, placing high-modulus chemical pulp on the outer plies and high-bulk mechanical pulp in the core to maximize bending stiffness relative to basis weight.
Converting Parameter
Carton packaging performance during automated feeding and pallet stacking depends directly on maintaining precise stiffness thresholds in both machine and cross directions. Inadequate bending stiffness causes carton panels to bulge under filling pressure and jam in high-speed cartoner suction feeds. Correlating laboratory stiffness values with packaging line runnability prevents structural carton failure during automated filling and distribution.