Cohesive Assessment
Quality control in adhesive bonding of paperboard packaging measures the percentage of the substrate surface area that experiences structural rupture rather than adhesive detachment during a pull test. This metric, known as fiber tear yield, indicates whether the adhesive bond is stronger than the internal cohesive strength of the paperboard itself. High tear values demonstrate that the adhesive has penetrated the fiber network to create a durable mechanical anchor.
Low values reveal that the adhesive has failed to establish an adequate bond with the cellulose fibers. This measurement helps packaging lines adjust pressure and dwell times during carton sealing.
Bond Failure
Evaluation occurs by manually or mechanically separating the sealed flaps of a carton after a specified set time. An operator or sensor inspects the failed joint to estimate the area where paper fibers have been ripped from the board. When the failure occurs entirely within the fiber matrix, the bond achieves maximum rating.
This failure mode shows that the adhesive layer did not fail at the interface.
Material Transition
Thermal conditions during application can alter the tear percentage. If the hot melt adhesive is applied too cold, it may freeze before wetting the paperboard, leading to a low fiber tear yield. This transition often occurs when temperatures in the facility drop.
The problem is resolved by optimizing the glue temperature.
