Plasticizer Migration: What is it and why is it a problem

Plasticizer Migration: What is it and why is it a problem

  

You’ve heard of plasticizer migration, but you aren’t entirely sure what it is and why it could be a problem. you will have a deeper understanding of plasticizer migration and its effects after you have read the article below.

 

What is plasticizer migration?

 

Plasticizer migration is the unwanted net movement of a plasticizer component out of a compound . 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.

The plasticizers can migrate from the PVC to 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?

 

. 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.

 

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. 

1. 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.
2. 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.
3. Coating the surface – The plasticizer cannot migrate out of the surface if there is a coating that will not allow it to pass through.