When something goes wrong with your bond, you want to know why so you can fix it. But, it may not be so easy if you do not know what you are looking for. There are many types of bond failure that could be the culprit.
What Is Bond Failure?
Bond failure refers to when two or more substrates that are supposed to be bonded together by an adhesive have separated. This occurrence can happen for several reasons such as poor surface preparation, improper curing, tough environmental conditions, incorrect adhesive quantity, wrong adhesive type, and more. Regardless of the exact reason, this adhesive bond failure usually falls into one of five categories.
The Different Types of Adhesive Bond Failure Explained
There are many ways something can go wrong when working with adhesives. If the substrates do not stay bonded, it is important to understand the different bond failure types so you can more easily get to the source of the issue and prevent it from happening again.
The five types of bond failure are:
Cohesive Failure
Cohesion refers to how molecules of the same substance stick together. Cohesive failure is a common type of adhesive failure that occurs when the adhesive itself breaks. In this case, the bonds between the adhesive and the substrates are stronger than the bond internally between the adhesive itself.
Cohesive failure may occur because the adhesive is too weak, not enough adhesive was used, or the bondline was too thick. This type of failure to bond is often seen with soft adhesives such as silicones or urethanes. Preventing more cohesive failure may mean choosing a different adhesive or altering how it is applied.
Adhesive Failure
Adhesive failure is a different type of bond failure that occurs when the adhesive hasn’t properly bonded to one of the substrates. This is also called delamination. This type of failure for bonds typically occurs when you try to bond dissimilar materials.
Adhesive failure can be the result of poor surface preparation, a low application temperature, or a long open time. It may also occur because the surface energy of the substrate was lower than the surface energy of the adhesive. Gluing polyethylene and polypropylene, for example, tends to be more challenging because of their low surface energy.
To prevent adhesive failure, you may need to do more preparation before applying the adhesive. You could also look for another adhesive that will bond better with the substrate that was part of the failure. Infinity Bond MMA 500 is one such product designed to bond to more difficult substrates like polyethylene and polypropylene.
Substrate Failure
Substrate failure occurs when the material itself has broken, not the bond from the adhesive. In this case, the bond is stronger than the actual substrate. Substrate failure is often seen as a more desirable result compared to other types of bond failure because it often means the adhesive is working as it should and was applied properly.
In some cases, you may need to reevaluate the joint design to prevent another substrate failure. Another option may be to use a more flexible adhesive.
Thin-Film Cohesive Failure
Thin-film cohesive failure occurs when the adhesive tears close to the surface of one of the substrates and only leaves behind a thin film of adhesive on that material. This film may be so thin that it is hard to see and can sometimes be mistaken for adhesive failure. Thin-film cohesive failure may be the result of using the wrong adhesive or not following proper adhesive surface preparation.
Corrosion Failure
Corrosion failure occurs when the adhesive separates from one of the substrates specifically because of metal corrosion. This corrosion makes bonding to the the surface of the substrate impossible. Corrosion failure typically occurs because of poor surface preparation or a low-quality substrate.
Correcting Bond Failure
Unfortunately, determining why a bond is failing and finding the right solution isn’t always easy, but we may be able to help.
If you are experiencing some type of bond failure, do not be afraid to reach out. Our adhesive experts can work with you to determine potential causes as well as solutions. Just contact us today.
