Rupture Measurement
Characterization of the internal bond strength of paper and board requires a standardized method to assess the resistance of the material to forces acting perpendicular to its surface. The iso 15754 z-direction tensile test specifies the procedure for determining this out-of-plane tensile strength. It applies a uniform tensile force to the surface of the specimen until delamination occurs.
This standard helps paper mills monitor the bonding quality of multi-ply boards to prevent blistering during offset printing. It ensures that the fiber layers will not separate when subjected to high-tack inks during high-speed runs.
Pulling Action
Preparation of the sample involves bonding the paper or board specimen between two metal platens using double-sided adhesive tape. The testing machine then pulls the platens apart at a constant rate of displacement to apply tension across the thickness of the sheet. This action isolates the internal fiber network.
It forces the failure to occur within the paperboard structure rather than in the adhesive tape.
Force Limit
Peak force measured at the moment of rupture is divided by the test area to calculate the tensile strength. This stress value is expressed in kilopascals or megapascals. The test ensures that the internal bonding can withstand the mechanical stresses of folding and creasing.
The analysis completes when the sample splits into two distinct layers.
