Factors to Consider When Applying Adhesives to Achieve Perfect Case and Carton Sealing

Proper sealing of cases and cartons is essential for maintaining the freshness and quality of products. It is also an important requirement for ensuring that the contents in a case or carton do not get damaged when items are being transported.

In most instances, case and carton adhesive applications involve using hot melt adhesives to seal flaps. An adhesive is applied at a high temperature to one flap, which is placed in contact with the other flap. These are then compressed to form a bond that will seal the case or carton.

If the bond works properly during the sealing process, it will be sufficient to hold a box or carton together until it is opened by the user. However, sometimes when opening a carton or case, the entire major flap shreds completely instead of easily opening and showing the fibre tear between two flaps.

Production teams involved with packaging strive to achieve optimal performance from hot melt adhesives. This requires an understanding of several factors that impact their performance. These include the substrate, the application temperature, amount of adhesive applied, compression time and open time.

Here are some factors which need to be considered when applying adhesives for sealing cases and cartons:

Glue Pattern 

In most case and carton sealing, hot melt adhesives are used to achieve the proper final packaging. These adhesives are applied in a bead form using high-speed, multi-orifice automatic glue guns.

An ideal glue pattern for packaging applications utilises a minimal amount of adhesive, sets quickly and has just the right pull amount required for opening the package flap.

Usually, the major flaps are being bonded—the large outer flaps—to the inner minor flaps. The adhesive is usually applied to the minor flaps. The major flaps are folded over and pressed against it. The adhesive then sets to form a tight seal.

Pattern length & width, compression and the type of glue 

These are all important factors in determining the amount of adhesive to be used for packaging.

The correct fit of an item being placed in a case or carton is also an important factor in determining the amount of glue to be used.

Under-filled or over-filled cases will require more adhesive for secure sealing due to the lack of consistent pressure/ additional pressure between flaps that are being compressed.

Environmental Factors

If products are packed in a warm area or a shipment of goods passes through cold or hot areas incorrect adhesive quantity could loosen bonds which can cause flaps on the carton to pop up.

In some packaging environments, the amount of adhesive to be used relates to packaging operation inefficiencies. For instance, if a corrugated case is not in a perfect square shape or if the compression system does not perfectly compress the flaps, applying more adhesive can compensate for the imperfections.


Several factors determine the adhesive temperature required to achieve optimal adhesive performance.

These include:

  • Adhesive heat stability
  • Substrate heat tolerate
  • Equipment limitations relating to open time and compression time

Coat Weight:

Coat weight is the amount of adhesive that is applied to create a bond. It determines the adhesive set up speed and also the surface area of the bond.


The compression time must be sufficiently long enough to allow the hot melt adhesive to develop the cohesive strength required to overcome the substrate memory or stress.

Open time

Theoretically speaking, open time should be the shortest possible to achieve the maximum wet-out and penetration of the secondary substrate. However, other considerations play a role.

These are:

  • Set speed of the adhesive
  • Physical space on the line
  • The pressure sensitivity of the adhesive

In addition to these common variables, other factors can also affect the performance of hot melt adhesives:

  • Changes in ambient conditions. For example, using a fan in hot weather conditions or opening of dock doors in cold environments.
  • Use of substrates stored in unheated warehouses that were not brought to room temperature before use.
  • Applying more quantity of adhesive to achieve a stronger bond. Excessive use of adhesive can cause slowing down of the set time which results in cases or cartons that open straight out of compression.
  • Switching to a new case or carton supplier.

Aside from these considerations, it’s equally important to choose the right adhesives. We stock a range of adhesives for case and carton sealing. You can check out our range of packaging adhesives by clicking here or call 07 3266 8699 to speak to one of our experts.