So The Glue Has Failed?
The glue has failed!!
Is there a simple way to understand how and why two glued materials come apart?
This is a topic which I am regularly asked about. As an example, the common question may be something like ‘how do I find out why and how the glue has failed’. In basic terms, a bonded part will fail through any of these reasons or a combination of them.
- The materials being glued have not been adequately prepared for gluing.
- The correct glue was used, but used incorrectly.
- The incorrect glue was used.
A glued joint may fail by way of two mechanisms, adhesive failure or cohesive failure. Let me explain further…….
Say we are making a sponge cake, with a layer of thick cream in the middle. If we pull both pieces of sponge in the opposite direction, and the cream only sticks to one side of the sponge, this would be regarded as adhesive failure. If the cream did stick to both sides of the sponge, this would be regarded as cohesive failure.
Optimally, the glue would fail cohesively (when the bond is broken, glue remains on both sides of the parts being glued).
Now to expand on the three points listed earlier, why would we experience glue failure? Well, it could be down to the materials. For example, the material may need to be primed, or solvent wiped, or abraded, or all three!!
Even with correct surface preparation, we still may see adhesive failure. In our experience, this is commonly due to the incorrect use of the adhesive. Typically seen situations include not letting films of solvent based contact adhesive ‘tack off’ before the bringing them together and incorrect mixing of two component structural adhesives.
In any operation involving the joining of materials, there is always enough room for error. Be it welding, riveting or adhesive bonding, many factors need to be taken into consideration.
Luckily, as Ireland’s only indigenous research based manufacturer of adhesives, sealants and structural tapes, we know the ‘ins’ and ‘outs’ of glue!
Until next time!
The Glue Guru.