TAPPI T 558

Bonding Evaluation

Shear stress calibration establishes the mechanical limits of multi layer paperboard used in folding carton production. Surface picking resistance determines whether linerboard withstands tack variation during high speed flexographic printing without lifting fibres from the substrate. Converters rely on these numeric indices to adjust starch pick up levels at the size press during manufacturing.

Laboratory technicians mount conditioned paper samples on an acceleration block and apply a standardized pressure sensitive tape across the felt side. Pendulum impact devices then strip the tape at a constant velocity, measuring the energy required to detach surface elements. Data output guides the selection of coating binders and refining intensity in the mill stock preparation plant.

Failure Threshold

Delamination boundaries occur when ink tack exceeds the internal bond strength established by the wet end chemistry of the paper machine. Low retention of colloidal sizing agents creates weak zones directly beneath the coating layer, resulting in catastrophic picking during multi color printing sequences. Offset lithography demands superior surface cohesion because tacky drying oils exert continuous pulling force on the blanket cylinder interface.

Packaging manufacturers reject production lots failing to meet minimum viscous pull tolerances because ink accumulation destroys half tone clarity on high speed converting lines. Refining degree and filler loading levels govern this threshold directly, establishing the maximum allowable pigment binder ratio for coated publication grades.