There are many applications of plastics in medical technology. Is the use of vitrimers a conceivable option in this setting?
Schubert: Yes, it is one of the aspects we are looking at in more detail. Think of implant materials with a protective layer on the surface to prevent tissue inflammation: You might consider using a type of plastic that can be recycled and healed to promote a prolonged use. Or you can use nanoparticles capable of releasing active ingredients when they are stimulated to support sustained use. These are all smart properties of polymers and plastics. To accomplish this, you need chemical bonds that you can break and form or that are able to reversibly switch back and forth. This is something you can achieve with vitrimers.
Are these types of applications already available?
Schubert: Some developments are nearing market launch, while several manufacturers are exploring patterns to see if they can be used. However, the licensing and certification process is a major obstacle in the medical technology sector. Typically, people are unwilling to accept limitations to material properties just to make a product "self-healing". It’s a characteristic they prefer to have “on top” of the other properties and it should ideally not be an added cost. That cuts down on the options. Having said that, the legislator puts pressure on entities to promote the recycling of composites. That is why we currently see an increase in research grants and funding.
How does plastic recycling work in this case?
Schubert: The previously mentioned wind turbine rotor blade is made of plastic and glass fiber. If you were to heat it above the ultrasonic temperature to where these bonds are broken, you could then pass the material through a sieve. The composite material – glass fiber etc. – would get stuck in the sieve, while the now liquid polymer is able to pass through. It could then be collected and solidified again once it cools down. This would allow its subsequent reuse.
Could this result in a loss of quality?
Schubert: You would have to prove that this is actually not the case. A present hurdle is the technical requirements pertaining to the flexural modulus or bending modulus of elasticity that must be met. We have to provide evidence of functional requirements specification that documents all protocols and standards and shows that we meet these criteria. Our research currently focuses on all these aspects.