Possible Problems When Bonding Hot-Melt Adhesive

Dissolving surfaces

  1. Cooling the adhesive during application prevents the formation of a good seam. A "good" tackiness can be created, which may be broken later when force is applied. Cooling can be caused by the following factors:
    • adhesive open time is too short for application;
    • application temperature is too low;
    • not enough glue;
    • air movement around the application area;
    • low ambient temperature;
    • bonding cold material.
  2. Package contents’ effects.
    • physically introduces additional stress into the seam;
    • chemicals or solvents soften the glue seam.
  3. Uneven application causes high stress in the adhesive joint.
  4. Poor pressing:
    • insufficient pressing;
    • movement of the bonded surfaces during joint consolidation.
  5. Replacement of the substrate that the adhesive can not glue:
    • reusable material;
    • more difficult for gluing material;
    • coated material (wax, lacquer) or impregnation.
  6. Improperly selected glue for the material or application:
    • insufficient heat resistance of the hot melt adhesive;
    • poor resistance to low temperatures, causing cracking;
    • insufficient adhesion to certain materials;
    • residual heat inside the package, which can shift the solidification point up to 24 hours in some cases

When the box leaves the packaging machine, the valve opens

  1. Open time is too short - the adhesive cools down before pressing.
  2. The temperature of the adhesive is too high - gluing does not occur in time.
  3. There is too much hot-melt applied - the adhesive does not seize in time.
  4. Poor alignment of the packaging surface – it increases the tension in the "raw" joint.
  5. The ambient temperature is high - the adhesive does not seize in time.
  6. The temperature of the substrate to be bonded:
    • too high - the adhesive does not seize in time;
    • too low - the adhesive cools down before pressing.
  7. Bad pressing.
  8. An improper hot melt type is selected.

Filament formation from the glue applicator

  1. Application temperature is too low.
  2. Air flow from open doors in the room.
  3. The nozzle is too far from the application surface.
  4. Unsuitable adhesive for the application method.
  5. Applicator malfunction.

Lack of hot-melt in the applicator head

  1. The equipment is insufficient to melt the glue.
  2. The melting system temperature is too low.
  3. Low glue melting speed.
  4. The level of glue in the tank was allowed to drop too low for proper replenishment.
  5. The applicator voltage is too low.
  6. Glue blockage in the pre-melting device or feed system; possibly due to the wrong size or shape.

Excessive vapours or odour occurrence

The temperature of the glue is too high:

  • incorrect adjustments may have been made;
  • the thermostat may be defective;
  • there may be a heater problem;
  • the glue tank may need to be cleaned.

Colour change of hot melt during application

  1. Contamination of the hot melt adhesive.
  2. Thermal decomposition due to application at a higher temperature than recommended. This can lead to the following consequences:
    • carbonization that forms solid particles;
    • carbon deposits on the walls of the reservoir, the supply hose and the injector;
    • viscosity change of the hot melt adhesive;
    • congealing throughout the system;
    • injector clogging.

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