You’ve heard of plasticizer migration, but you aren’t entirely sure what it is and why it could be a problem. There could be several reasons why you’re experiencing plasticizer migration, but you just want to know a little more about it.
Here at Forgeway, we manufacture industrial adhesives. We often come across instances where plasticizer migration impacts the performance of the adhesive. So we understand what it is and the effects it can have on adhesives.
That is why we wrote this article. We want to help you understand plasticizer migration and the effect it can have on your adhesive products. By the end of this article, you will have a deeper understanding of plasticizer migration and its effects.
What is plasticizer migration?
Plasticizer migration is the unwanted net movement of a plasticizer component out of a compound (like an adhesive or plastic). It can occur through gas volatilisation, liquid extraction, or solid migration. Collectively these are known as plasticizer migration.
Plasticizers are often put into materials to make them more flexible or malleable. As an example, PVC is heavily-plasticized to increase its flexibility. So when bonding PVC with adhesives, those plasticizers can migrate from the PVC into the adhesive.
Plasticizer migration is more likely to happen in certain circumstances. For example, if there is little interaction between the polymer and the plasticizer (it hasn’t mixed well), plasticizer migration is more likely to occur.
Why is plasticizer migration a problem?
You may be wondering why we, as an adhesive manufacturer, are writing an article about plasticizer migration. We sometimes see plasticizer migration becoming a problem when our customers use adhesives. We will describe the different problems that plasticizer migration can cause.
Plasticizer migration can cause Environmental Stress Cracking
When some plastics are under stress, they can develop hairline cracks known as environmental stress cracking. If other components (such as adhesives) come in contact with an area of plastic under stress, then certain chemicals within these other components can accelerate the stress-cracking process.
Migration of plasticizers through these other components to the surface of a plastic under stress is a likely culprit to blame for environmental stress cracking. So in the right conditions, plasticizer migration can cause environmental stress cracking to take place.
Plasticizer migration can impact a products performance
A plasticizer’s main purpose is to increase a product’s flexibility. So when the plasticizers migrate out from that product, flexibility can go with it. This then causes embrittlement.
In the case of adhesives, this can cause the adhesive to become unfit for use in an application. This is particularly the case if the adhesive is in an application that requires flexibility.
It’s not just about flexibility though. Plasticizer migration can cause other additives to migrate too. Typical examples of these additives are UV stabilisers or Anti-Oxidants. If plasticizer migration causes these additives to migrate, the overall performance of the adhesive will deteriorate.
Plasticizer migration can affect the aesthetics
There are several occasions where plasticizer migration can have aesthetic effects.
- Fogging in glass automotive applications – The plasticizer in an automotive dashboard application outgasses, causing the glass around it to fog up.
- Paint issues – Migrating plasticizers can damage the finish of the paint. They can also cause issues when painting over.
- Dirt pickup – Plasticized adhesives can become sticky on the surface and pick up dirt. This dirt pick-up affects the aesthetic of the adhesive.
- Plasticizer leaching – When plasticizers migrate out of a compound, they can bring pigment with it, causing the pigment to ‘leach’ down the substrate.
Plasticizers can be toxic
When an adhesive is in a medical, dental, drug, or food application, there is the risk of plasticizers causing harm to humans. The plasticizer in the adhesive will have to be carefully chosen to ensure it doesn’t harm humans.
It’s not only humans these plasticizers can harm. They can have environmental impacts too. Ecosystems get damaged through the bioaccumulation of plasticizers.
Can you prevent plasticizer migration?
The simple answer is yes, you can prevent plasticizer migration. When formulating a polymeric compound (like an adhesive or plastic), manufacturers can take steps to prevent it from taking place.
But you can take preventative measures yourself. You will need to have an understanding of the adhesive and the plastic you are using. Once you understand the level of plasticizers in your materials, you can decide whether or not you need to be doing something about it.
There are three main ways you can prevent plasticizer migration.
- Use specialist plasticizers – Plasticizers with a high molecular weight or a high degree of branching will prevent movement. Plasticizers with high molecular weight will find it difficult to migrate due to their size in the network they are bound in. Plasticizers with a high degree of branching will become entangled in the network, meaning they will find it difficult to move.
- Use a reactive plasticizer – Reactive Plasticizers will chemically graft into the polymer matrix. This means it is much more difficult for the plasticizer to migrate out of the material.
- Coating the surface – The plasticizer cannot migrate out of the surface if there is a coating that will not allow it to pass through.
Choosing an adhesive to avoid plasticizer migration
Now that you know about plasticizer migration and why it causes problems, it’s time to decide whether it can affect your application. You will want to know whether plasticizer migration is going to affect your bond.
Here at Forgeway, we manufacture industrial adhesives. We often help our customers overcome issues with plasticizer migration as it is a complex topic with some critical factors to consider. Your adhesive choice could make a big difference on the impact of plasticizer migration.
But choosing the right adhesive for your application is never easy. There are so many different factors you need to consider. You may struggle to know where to start. That’s why we want to help you.
An adhesive expert is just a click away from helping you choose the right adhesive. Or, if you are the independent type, you can work it out for yourself. You will need to assess the different factors you need to consider when choosing an adhesive. The article below will give you an overview of those different factors.
