“Plastics help to reduce CO₂ and conserve resources”

Mr. Düssel, today the word “plastic” makes many people think of microplastic particles in food or the Great Pacific Garbage Patch. But you regard plastic as an especially sustainable material. Why?

Most people don’t have a problem with plastics as such. However, they’re concerned about the careless way plastics are being dealt with, especially in the area of disposable products. We need plastics to solve the huge challenges that confront us today, ranging from the thermal insulation of buildings to modern concepts of mobility, digitalization, and the expanded use of renewable energy sources. No wind turbine spins without plastics. No train runs without plastics. No mobile phone functions without plastics. Plastics help us to make products smaller and more robust. In many cases, that reduces CO₂ and conserves resources. By comparison with glass, metal, and wood, plastic weighs less, is easier to process, and is more durable in many applications.

What role do high-performance polymers play in these areas?

They are used wherever standard plastics such as polyethylene and PET aren’t up to the job—for example, in the production of small and moving components or in products that are subjected to extraordinary environmental and climatic conditions or high levels of thermal and mechanical stress. These high-performance polymers are rarely found in packaging, but they are often used in machines, electric appliances, furniture, and high-quality design objects. Polyamide 12 is used in automobile production and the manufacture of consumer goods, among other things. 3D printing is creating brand-new areas of application for powder or filaments made of this high-performance polymer. 

What properties make a plastic a “high-performance polymer”?

The more specific a material’s characteristics are, the more challenging is its production process and the smaller is the amount produced. Although several tens of millions of tons of the standard plastic polypropylene are produced every year, only a few tons of polyether ether ketone (PEEK) are produced. In the well-known pyramid of plastics, the standard plastics form the base and the high-performance polymers form the tip. Between them are the technical plastics such as polyethylene terephthalate, which is used for PET bottles. 

Why are these top-rated materials so interesting for researchers?

Because they can be developed to perfectly fit specific applications. If customers have very specific requirements, high-performance polymers often offer the properties that are needed. For example, battery casings for electric vehicles have to be especially lightweight and heat-resistant. In addition, they have to optimally protect the battery from damage in case of a collision. Here’s another example: Since the 1970s, the proportion of plastics in airplanes has increased from four to approximately 50 percent. That’s another reason why today airplanes consume less kerosene and fly for longer periods of time. Developing materials that fulfill such demanding requirements is very exciting.

What application has been the most impressive for you personally?

One important area of application for these materials is medicine. Just last year, an initial set of patients received vertebral implants that had been completely 3D-printed using PEEK. In Europe we now have the first clinics that print individual cranial implants themselves for people who have sustained serious head injuries in an accident. And just think of the children for whom 3D printers are creating customized prostheses that hardly weigh anything and enable the kids to regain more mobility. These solutions are hugely improving the patients’ situation and directly supporting their recovery. 

What role is played by the combination of high-performance polymers and 3D printing? 

Customized applications are becoming increasingly important—and that’s exactly where high-performance polymers are demonstrating their strength. They make it possible to produce small batches very flexibly. This means that replacement parts that are no longer available can be created individually in a 3D printer. This will help to repair high-quality products and machines more easily and inexpensively. In the future, the right to repair will affect more and more areas of industry, and high-performance polymers can play an important role there. 

In the years ahead, will there be completely new materials that can be used to produce high-performance polymers? 

This is certainly an exciting time for researchers working in this area. Again and again, we’re seeing new challenges that can sometimes be solved with a monomaterial and at other times with a composite. 

However, in recent years we haven’t seen any completely new monomer that plays a role on an industrial scale. Why is that?

It’s true that ideas for new monomers are constantly cropping up. Evonik too regularly tests new materials. But there are high hurdles that a completely new material has to overcome with regard to its scalability. When plastics processors are selecting materials, a crucial role is played by factors such as specific weight, prices, and availability, as well as the CO₂ footprint and recyclability. Many requirements can already be basically met by the high-performance polymers or composites that are available today. When a new monomer offers a crucial advantage only in a very specific application, the market is often too small for this new product to be commercially successful. 

High-performance polymers are comparatively expensive. Is there a danger that they will be driven out of the market by advanced standard plastics?

It’s true that better additives, as well as progress in the area of processing, have improved the performance of standard plastics. For example, if you touch a piece of artificial leather today, you can hardly tell it apart from genuine leather. However, if especially stringent requirements are set regarding durability and robustness, there’s no alternative to high-performance polymers. Thermal and electric insulation properties play a huge role in many applications. Applications in automobiles require crash resistance and radar transparency for the sensor system. In plant construction, low levels of material fatigue, as well as resistance to chemicals and X-rays, are crucial. And in the area of prosthetics, the important qualities are biocompatibility, biostability, and bone-like mechanical properties. All of these conditions are fulfilled only by high-performance polymers. 

How can the sustainability of plastics be further improved? 

It’s important to look at the entire life cycle of a product. It already begins with the design. Products must be designed so that they need as little material as possible to manufacture and that at the end of their life cycle their various materials can be easily separated from one another. 

However, even if the product has been used as economically as possible, the problem of disposal remains.

It’s essential to systematically collect plastic waste and feed it back into the cycle. However, high-performance polymers are often produced in small quantities and processed in long-life products such as automobiles or large machines. So it’s not easy to recycle the material and reuse it after the end of these products’ life cycle. So far, it has seldom been worthwhile for mechanical recyclers to extract high-performance polymers and correctly sort them according to type. That’s why this kind of plastic waste still lands in the incinerator much too often. We have to change that!

How could this plan work? 

There are several possible starting points. Some plastic producers are working to develop recycling systems. For example, for every correctly sorted kilo of material that is delivered to them, they offer a discount on the next order. Chemical recycling is another option. This makes it possible to break down even mixed and soiled high-performance polymers into their chemical components and transform them into new raw materials. Digital product passes and tracing technologies can also help with the AI-controlled collection and sorting of high-performance polymers in automated sorting facilities to obtain pure materials for recycling.

Is it necessary to cut back on performance so that plastics can be recycled more easily?

If special solutions are required, today we can sometimes use composites or materials whose properties are improved by means of additives. For high-performance polymers of this kind we need special recycling processes that are already being worked on. High performance is not incompatible with recyclability. We must continue to do intense research in areas such as replacing composites with new and very high-performance monomaterial plastics. 

Are recyclates or alternative raw materials suitable as a basis for high-performance polymers?

Yes. Plastics made from chemically recycled materials have the same quality and material properties as new materials made of fossil raw materials. And of course the carbon that is needed for producing high-performance polymers can also be derived from biomass and CO₂. Today 19.5 percent of all newly produced plastics in the EU already consist of circular raw materials, and this proportion will go on growing. Evonik also has a broad portfolio of high-performance polymers that are already based partly or wholly on biomass. In the process, we are relying on the mass balance system…

…in which the bio-based raw materials are not used directly but are ensured by means of a certification, so that the corresponding amount is fed into the system as a whole. Why is this path necessary?

Because this is how we can directly use even small amounts of bio-based or recycled raw materials. That’s because the available amounts are often so small that it wouldn’t be possible to operate a separate facility or production line with them. 

What plastic product is still missing in your life?

I’m looking forward to air taxis, and I hope they appear as soon as possible. That would would be a new mobility option, for example, thanks to high-performance polymers in the rotors.