Possible Problems When Bonding Hot-Melt Adhesive

Dissolving surfaces

  1. Cooling of the adhesive during application that prevents making a good seam. A "good" tackiness can be formed, which is broken when the force is applied later on. Cooling can be caused by the following factors:
    • open time of the adhesive is too short for application;
    • application temperature is too low;
    • not enough glue;
    • air movement around the application area;
    • low ambient temperature;
    • cold material to be bonded.
  2. Effects of package contents.
    • physically introduces additional stress into the seam;
    • chemicals or solvents soften the gluing seam.
  3. Uneven application causes high stress in the adhesive joint.
  4. Poor pressing:
    • insufficient pressing;
    • movement of the bonded surfaces during consolidation of the joint.
  5. Replacement of the substrate that the adhesive can not glue:
    • reusable material;
    • more difficult for gluing material;
    • the coated material (wax, lacquer) or impregnation.
  6. Improperly selected glue for this material or application:
  7. insufficient heat resistance of the hot melt adhesive;
  8. poor resistance to low temperatures, causing cracking;
  9. insufficient adhesion to these materials;
  10. residual heat inside the package, shifting 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 on time.
  3. There is too much hot-melt applied - the adhesive does not seize on 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 on time.
  6. The temperature of the substrate to be bonded:
    • too high - the adhesive does not seize on time;
    • too low - the adhesive cools down before pressing.
  7. Bad pressing.
  8. The TM of hot melt is incorrectly selected.

Formation of filaments from the glue applicator

  1. Application temperature is too low.
  2. Screws because of the open doors of the room.
  3. The nozzle is too far from the application surface.
  4. Unsuitable adhesive for this application method.
  5. Malfunction of the applicator.

Lack of hot-melt in the head of applicator

  1. There is not enough equipment to melt the glue.
  2. The temperature of the melting system is too low.
  3. Low glue melting speed.
  4. The level of glue in the tank was allowed to drop too low to replenish.
  5. Too low voltage of the applicator.
  6. Blocking of the glue in the pre-melting device or feed system; possibly due to the wrong size or shape.

Excessive occurrence of vapors or odor

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.

Color change of hot melt in work

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

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