22. 11. 2019


Adhesion of covering materials: the influence of the panel.

Tags: Surface finishes adhesion

In these short notes we would like to present a real case of an adhesion defect found in the course of our daily activity of analysis and support to companies on the cases of defects, considering the importance of the wide use of covering materials (papers, laminates, polymeric foils) in the current market situation.
Specifically, it was a gluing problem reported on a laminate applied on a particle board.
At the end of the production process, in fact, it was evident a partial lifting of part of the laminate that could be removed from the surface of the panel in a relatively easy manner, simply by exerting a slight tearing force on the laminate itself.
The problem described was only found on the new production, while on the previous lots no such situations had ever emerged. Furthermore, according to the manufacturer information, no changes were made to the bonding process and a careful inspection of the production parameters did not seem to indicate any malfunctioning of the systems or other criticalities related to climatic conditions or accidental events.
After considering together with the company a whole series of possible hypotheses, it was decided to proceed with an investigation on the characteristics of the raw particle panels used in the new and old processes.
This appeared, in the first instance, the only possible variable linked to the alleged defect.
Two tests were then carried out:

  • the surface water absorption according to the European standard EN 382-2; 
  • the resistance to detachment of the outer layers according to the European standard EN 311 (Surface soundness). 
In the first case, the increase in weight of the panel is recorded after having placed in contact with its surface a certain quantity of water enclosed within a given area.

The second test, on the other hand, involves the gluing of appropriate metal elements to the surface of the panel, which are subsequently pulled off with a dynamometer forcing the cohesion of its outer layers. The result is expressed by the force necessary to overcome the superficial cohesion of the panel.
This test showed a difference of about 20% between the two panels with a significant lower resistance for those of the new production.
But the most significant figure was that relating to the water absorption, which was much higher, around 75% more, for the panel used in the new production than the previous one.
It has therefore been concluded that the difference found in surface absorption may evidently lead to a greater penetration of the adhesive inside the panel of the new production, thus affecting the bonding process or making it weaker due to a lower quantity of adhesive, which remains on the surface after its application.
Finally, this experience suggests that the surface absorption of the panels represents a parameter that must be carefully considered in the development of the covering processes, since it can determine, for example, the need to apply different weights or even to use an adhesive with a selected proper viscosity.
Finally, we report that considering the evolution in this type of processing and the problems associated with it, by 2020 Catas has already planned a specific seminar in order to deal with these issues.

For info:
Franco Bulian
+39 0432 747231