Coperion's Peter von Hoffmann on the one extruder that handles every polymer : "Modularity is a genuine advantage"

How has your product lineup changed over the past five years, particularly regarding material-specific requirements? Are you seeing more specialised machines and fewer general-purpose models?

As we evolved into the recycling market, we realised that the raw materials we work with are quite specific, and so we had to adapt our machinery accordingly. We developed equipment capable of handling low-density, fluffy material — the kind you typically encounter in recycling. Post-consumer films, for instance, are sliced and diced, reduced in size, and become very airy and voluminous. Getting that material into the machine efficiently is a real challenge, and we have developed a range of units specifically to address this. That evolution has made us considerably more capable in this space.

What drove the decision to move into the recycling market?

The topic had been growing steadily. We started — I would say — more than ten years ago, perhaps fifteen, through increasing contacts with compounding companies and, later, downstream recycling companies. We recognised we needed to expand our offering in that direction.

Then came the legislative turning point: Asian countries, most notably China, decided to stop importing post-consumer plastic waste. The market essentially skyrocketed overnight. That was the moment when we shifted recycling from a side chapter into a genuine focus area.

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Twin-screw extruders are highly regarded, but are there materials or situations for which a single-screw extruder would be the better choice?

It is more a question of output scale. At lower outputs, other systems — including single-screw extruders — can deliver sufficient quality. But once you reach roughly one ton per hour, the twin screw's advantages become clear. Single screws have inherent limitations at higher outputs.

Above that threshold, the twin screw enters its sweet spot. It delivers excellent homogenisation, effective degassing to remove volatile content, and all of that without damaging the product — no gels, no degradation. That combination is what sets it apart.

Is the demand for twin-screw extruders also driven by the larger material volumes customers now need to process?

Yes, exactly. When China closed its borders, the available material streams became much larger. Suddenly there were significantly higher volumes to process. Before that point, recycling was more of a local affair: modest volumes, local operators. When the streams grew, so did the required tonnages. Our machine was very well suited to meet that demand.

Looking at food-grade PET versus contaminated post-consumer polyolefins — is there a meaningful cost difference between the extruders required, and if so, what drives it?

The technology used for the recycling process needs to complete and pass a challenge test to achieve food-grade approval. We have done this for PET, and have just received the Letter of No Objection (LNO) from the U.S. Food and Drug Administration (FDA) for PP HDPE. 

The extruder itself does not necessarily cost more if the recycled material is intended for food contact. Twin screws are inherently well suited for food-grade production: the shear conditions, temperatures, and residence times inside the machine provide the required process conditions without extra design complexity. 

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Many customers process more than one type of plastic. Is there a trade-off between running a highly specialised line versus a more general-purpose one? How do you advise customers on that choice?

The twin screw's great strength is its flexibility. These machines routinely process all polymer types — ABS, polystyrene, polyamide, polyolefins, PET, and more — without requiring fundamentally different setups.

The machine is also highly modular. Barrel segments can be exchanged, and the screw itself is made up of segmented elements that can be rearranged. We have a sizeable processing team here in Stuttgart whose job is precisely that: to review a customer's screw profile, modify the configuration, and adapt it to different products. On a single-screw extruder, you would need to order an entirely new screw. On a twin screw, you simply rearrange segments. That modularity is a genuine advantage.

And in terms of output quality — is that consistent across all the different polymer types you mentioned?

Across a very wide range of applications, yes. The processing window is broader than anything I know of in comparable systems.

You mentioned your test center. How much of Coperion's R&D is directed toward material-specific customisation versus general equipment improvements?

Our test labs serve two purposes: development and demonstration. We have invested significantly — I won't give exact figures, but it runs to several million euros — in our Recycling Innovation Center in Weingarten,Germany. We also run recycling trials at our test lab in Stuttgart, and we have further centers around the world covering different equipment types.

In terms of the split: roughly two-thirds of trials are customer-specific demonstrations and developments; around one third is internal research. 

So customers come to you with a specific challenge and you develop a solution together?

Absolutely. Customers bring specific raw materials and specific quality requirements — and they want proof that the process will work before committing to multi-million investments in a plant. We demonstrate that. Sometimes it is about mixing and homogenisation in the mechanical recycling process; sometimes the question is simply whether the material can be fed into the machine at all. For that, we use our feeder lab. Sometimes it is about conveying — moving material from A to B and discharging it from containers. We prove each piece of equipment individually.

When we develop something new ourselves, the test lab is also where we validate the performance gain — whether it delivers improved throughput, better product quality, or something else entirely.

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Have customer requirements changed in recent years — with new legislation, or with the arrival of AI-driven sorting that is producing better-sorted feedstocks?

The clear direction is: recycle more. The straightforward streams may already be well addressed, and the more complex challenges are driving us toward chemical recycling. When you have a clean, well-sorted stream, mechanical recycling keeps the material in the loop as long as possible — and that is always the preferred route. But when you have a highly mixed or variable feedstock, chemical recycling becomes the right answer.

We have pilot and first commercial lines for chemical recycling that have come on stream in recent months in Europe. In my view, chemical recycling is the end-of-life solution for difficult-to-sort or degraded materials. Through pyrolysis, the plastic is converted back into oil, and from there it can re-enter the cycle as a virgin polymer feedstock.

Is chemical recycling already economically viable?

That is genuinely difficult to judge. It depends heavily on the feedstock mix, the yield you achieve, and the energy costs — or energy source — behind the process. Whether it makes ecological sense hinges on those same factors. In an ideal scenario, you use renewable energy to drive the process and keep oil-based plastics circulating in the loop instead of extracting new crude. The demand for plastics is not going away; the point is to keep the source material in the cycle.

Coperion is also working with blends of virgin and recycled material. Does combining the two create additional complexity in the extrusion process?

Blending has actually been done for many years — long before recycling became a hot topic — primarily for economic reasons. People wanted to reduce raw material costs, and in-house recycling was common practice.

A good example is a customer of ours with a multilayer packaging film operation. He has a zero-waste concept: when you produce film, there is always edge trim and off-cuts that used to be sold off for external recycling. Now he keeps that material in-house, runs it back through one of our twin screws, and feeds it as a pre-mixed compound into certain layers of his film. In years focused on sustainability, that gives him an ecological credential and a commercial story. In years when raw material prices are high, it saves him the cost of buying virgin polymer. It works in both directions.

And for the equipment itself — does the blend ratio require significant adjustments?

Minor adaptations, yes. Virgin polymer alone is predictable and straightforward. When you add rework pellets — which is standard practice now; most compounding lines include a dedicated rework feeder — our processing team will review the screw profile and perhaps extend the melting zone. But it is not a major reconfiguration. The extruder accommodates it readily.

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How quickly can the machine switch between different materials or recipes within a single production day?

Very quickly, in practice. We have customers who run batches as small as ten kilograms. On a machine processing 100 kg per hour, you barely have time for a coffee before the lot is done and you need to change over. They do this day in, day out.

Production planning is the key. Operators identify which recipes share the same screw profile and sequence jobs from light to dark colours over the course of a day. At a natural break point, they carry out a cleaning cycle or a screw change — which on a medium-sized machine takes one to two hours — and then move to a different product type with a new screw configuration. That kind of daily flexibility is routine for both compounding and recycling operations.

Does the degassing capability also transfer across different materials — can the same vacuum setup handle a wide range of polymers?

Yes, for the most part. For around 80 per cent of applications, a standard vacuum pump  will handle a wide range of polymers and degassing tasks. Where it gets more specialised, for example with PET where you want a lower vacuum level, you add a second pump in series. The size and sophistication of the vacuum system can scale up, and where greater performance is needed you can add separators or additional stages. But the fundamental flexibility of the system remains.

Does chemical recycling and pyrolysis require a significantly different extruder design?

Yes, the design requirements are quite different. Chemical recycling plants operate at much larger scales — outputs of six tonnes per hour are common, corresponding to a screw diameter of 133 mm, for example. Compare that to a mechanical recycling line running one tonne per hour on a 70 mm screw.

The objectives are also different. In chemical recycling, the aim is to fully melt the material, capture and trap unwanted substances — chloride traps for PVC, for instance — degas the melt, and then bring it to as high a temperature as possible, typically around 350°C, before it enters the pyrolysis reactor. Delivering material at that temperature means less external energy is needed downstream. In mechanical recycling, you do the exact opposite: you minimise temperature throughout to avoid further degrading the product.

Is demand for chemical recycling technology actually growing? Are you seeing more enquiries?

I would not describe it as booming at this moment, but a number of large players are building pilot lines and gaining hands-on experience. They want to understand how well the process works, what proportion of their material streams it can cover, and how to meet voluntary recycled-content targets. That interest is sustained and continuing to grow.

What kind of people do you look for when staffing your labs and development teams?

"Smart people. Motivated, internationally active, open people." That is what we look for. We do have a very high density of engineers — in our processing team, our sales team, our project management team. Engineering is clearly the dominant discipline here. But fundamentally, we are looking for people who are enthusiastic and capable of pushing these topics forward.

Is there meaningful collaboration across the industry to drive innovation — with universities or research institutes, for example?

Very much so. We work closely with a number of institutes, including a university here in Stuttgart, and we have lab-scale machines placed at universities and research institutes around the world — both private-sector organisations and state universities. Our processing and development teams maintain close, ongoing relationships with those partners. The larger industrial companies also have their own R&D teams, and they interact directly with us as well.

Is the R&D focus more on handling new or emerging material streams, or on optimising performance for materials customers already process?

Both, genuinely. Customers often have a defined portfolio of materials they compound or recycle. But then a new customer arrives with an attractive volume and an unfamiliar feedstock. Our processing team engages with them, and we try to help our customers win those orders — in the expectation that success leads to new machine purchases further down the line. At the same time, existing customers continuously ask us to optimise their current processes. It really is both.

Do legal regulations — including elements of the European Green Deal — have a significant influence on your market?

Definitely. We saw this clearly when certain jurisdictions banned single-use plastic shopping bags — our biopolymer line boomed as a result. The same dynamic applies in recycling: the industry is essentially waiting for mandatory recycled-content quotas to come fully into force. When they do, demand for our equipment will accelerate sharply. The uncertainty right now is whether and when those requirements will be finalised and enacted.

Looking globally — where do you see the strongest growth in demand for plastic recycling technology?

All three main regions: Europe, Asia, and North America. We have active recycling projects in all of them.

Europe is driven by legislation and already robust environmental standards. North America is perhaps surprising —many companies there operate with environmental responsibility, and brand owners with large packaging volumes stick to their recycling commitments. In Asia, China remains a significant market, and India is increasingly important — there is strong activity there right now, and we have sold lines in that region. Even in Africa, we are beginning to see genuine interest in recycling investment.

Finally, do you expect the market to move toward greater specialisation with material-dedicated lines, or toward even more flexible, multi-purpose equipment?

Honestly, both trends will coexist. In traditional compounding we already see a move toward larger scale on one hand and greater flexibility at smaller scale on the other. I expect recycling to follow the same pattern.

There will be operators identifying niche feedstocks and requiring flexible, adaptable equipment. And there will be large commodity-scale streams where the economics justify a single dedicated high-capacity line. We provide solutions for all types of systems — from small recycling extruders and individual components to complete turnkey recycling plants, including grinding and washing lines at the front end and the compounding system at the back, delivering a finished, specification-grade compound.