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“Everyone always says ‘thermoplastic composites are 100% recyclable.’ And they are — it has been proven you can do it. But nobody’s really doing it,” says Winand Kok, co-founder of . (Spiral RTC, Enschede, Netherlands).

Thermoplastics are considered to be inherently recyclable because thermoplastic polymers, by definition, are able to be melted down and then remolded into a new, usable form.

Recycling thermoplastic composites (TPC), given the addition of fiber reinforcement, is a bit more complicated, but there are a variety of methods developed for recycling TPC. These include thermal and chemical processes for separating the fiber from the resin — but these, generally speaking, are focused on reclamation of the higher-value fiber without taking advantage of the more recyclable properties of the resin.

Spiral RTC is focused on mechanical recycling of TPC, which involves shredding or milling an entire TPC part or scrap material, and then melting it down into material that can be reprocessed into injection moldable pellets to manufacture new parts. Kok and co-founder Hans Luinge started Spiral RTC in 2022, inspired by years of experience at thermoset and thermoplastic composite materials supplier Toray Advanced Composites (and its predecessor TenCate Advanced Composites), where they recognized firsthand the need for TPC waste solutions.

Recycling scrap materials is vital to a manufacturer aiming to reach internal sustainability and emissions goals, or to meet current or future sustainability regulations. Beyond sustainability, though, there are also a variety of practical reasons for a materials supplier or fabricator to recycle TPC scrap, Kok says. These include decreasing the amount of waste generated, minimizing disposal costs of transporting waste to landfills and — for those with applications suitable for the recycled material — allows for less dependency on raw materials.

As they began researching TPC recycling solutions more seriously, Kok and Luinge realized there was a need for an independent recycling company that is small enough to be flexible and adaptive to the needs and changes in the market. “The goal is to be an independent hub in the center of the market, able to collect waste from a variety of sources in the supply chain. This isn’t easy if you’re just the recycling arm of one large material manufacturer, for example,” Kok says.

For the process technology, the partners decided to advance mechanical recycling methods that have already been proven. “The background starts 30 years ago with scientific papers, proving that [TPC recycling] can be done in the form of mechanical recycling and compounding into an injection molding compound,” Luinge explains. “The next logical step was to make demonstrators, to prove that the academic research can be done on a practical level. A lot of successful demonstrators started appearing, from the TPRC [ThermoPlastic composites Research Center] but also GKN Aerospace and Clean Aviation, and others. From there, the next logical step is implementation on an industrial level, and that’s where Spiral RTC comes in. It’s all based on the foundation of research and technology that’s been in development for decades.”

Kok adds, “There are many challenges and considerations when trying to scale from an academic lab process to an industrial recycling level.” These include securing a steady supply of materials, addressing technical challenges associated with processing variable materials, ensuring efficiency at a larger scale, developing applications for the recycled materials and waste treatment regulations. “There were — and still are — a lot of questions to answer,” he says.

Kok and Luinge began by partnering with the TPRC on several successful R&D projects, and Spiral RTC has an office on-site. The company’s recycling operations take place in a refurbished aircraft shelter at a nearby former airfield, Twente Airport.

Recycling operations, supply, end products

Spiral RTC’s business model comprises three steps: 1) collecting waste, 2) converting it into usable material and 3) commercializing it again — in other words, finding an application for it. “All of these parts need to grow more or less in parallel for any recycling business to work,” Luinge says.

At its production site, Spiral RTC stores, classifies and cleans incoming waste material, and mechanically shreds it into smaller sizes — typically smaller than 1 × 1 inch. The processed regrind flakes, which combine both the short fibers and residual resin, are then delivered to a compounding partner where they are melted down and converted into pellets. These pellets are then returned to Spiral RTC to supply to companies with applications for recycled TPC.

Spiral RTC currently processes more than 10 metric tons of waste material per year — “still small, but considerably larger than an R&D project,” as Kok describes it. “It’s a really straightforward process. We aren’t trying to reinvent recycling, we’re trying to implement proven concepts and build it up to a commercial level.”

CFRTP supply: Controlled, aerospace-grade prepreg

Currently, Spiral RTC receives carbon fiber-reinforced thermoplastic polymer (CFRTP) material scrap directly from material suppliers or end users (like Collins Aerospace, as described in CW senior technical Ginger Gardiner’s plant tour of the manufacturer’s Netherlands facility).

“In terms of value, we’re starting from well-controlled, high-end, aerospace-grade, long fiber CFRTP aerospace materials with high-performance polymers from nylons and up,” Kok says. Typical materials are carbon fiber-reinforced PA, PEI, PPS or PAEK. “You are sacrificing some of the value in the length of the fibers, but there’s high economic value and technical performance in these materials still — which is important, otherwise there’s not a business case for doing it.”

He emphasizes that a business case is necessary. “We are not waiting around for legislation to force people to reuse waste, because that takes too much time. We can only do this if it makes sense economically for all parties.”

The materials choice also has to make sense ecologically. “If you take, for example, a glass fiber-reinforced polypropylene, and do the life cycle analysis, it might not actually make sense to recycle it, ecologically or economically,” Luinge explains. “But it’s so energy-intensive to manufacture carbon fibers and these high-performance polymers that it makes sense to use this manufacturing scrap rather than throw it away.”

As the company prepares to accept materials from more sources in future, Spiral RTC is also working to solve potential challenges related to efficient material collection, accurate identification of material types and separation of different materials. “This requires time and working together with different stakeholders, so we’re starting now to have a solution ready for the future,” Luinge says.

Kok adds, “I know volume is a valid question, and one we’re always conscious of, and have backup plans in place. The volume is still small, unfortunately, so we combine similar materials from different sources, but we have plenty of supply at the moment.”

What about CFRTP parts at their end of life (EOL)? Currently, this is an area of research for Spiral RTC. Through aerospace industry partners, the company has acquired several glass fiber-reinforced PEI smoke detector pans that flew on now-decommissioned commercial aircraft (see CW’s original coverage of the pans’ design in 2013). The Spiral RTC team dismantled and shredded the components, and these will be compounded into injection molding pellets and tested to see how the properties compare to similar virgin materials. “This is a case study using the parts we have available to see how to deal with EOL parts, to understand the complexity involved,” Kok explains.

End products and applications

Spiral RTC works with compounder (Witcom, Etten-Leur, Netherlands). Typically, the recycled material is mixed with neat polymer and/or other additives such as lubricants during the compounding process to create a new compound. The challenge is to convert the regrind flakes into a form that can be processed in standard compounding equipment, while maintaining needed stiffness and strength properties in the final product. “It’s been an iterative design process, but one that Witcom has invested in,” says Nico Harperink, technical sales manager for engineering plastics at Witcom.

In addition to injection molding pellets, Spiral RTC is also working on pellets for large-format 3D printing, as well as forged carbon intermediates and bulk molding compound (BMC). The BMC work is being done in collaboration with the TPRC and its sister organization ThermoPlastic Composites Applications Center (TPAC), with the goal of creating a product that can incorporate material with longer fiber lengths.

What types of applications can these materials be used for? One area with a lot of potential is industrial applications — such as bearings — that can benefit from the strength, stiffness and chemical resistance of recycled carbon fiber (rCF). “It’s not a drop-in replacement, but these materials are relatively easy to use,” Kok says.

Spiral RTC recently worked with a pump manufacturer partner to develop a complex rCF/PPS pump casing for use on an industrial dewatering pump. The 9-kilogram, 56 × 43 × 16-centimeter part, typically machined from cast aluminum, can be manufactured more cost-effectively with injection molding.

Why the choice of rCF/PPS? Kok explains that the PPS resin provides the required moisture and chemical resistance, while the rCF is high enough quality to add the necessary dimensional stability. “It is a great example of the use of our circular materials, originating from aerospace composites, now used in injection molded machine components,” Kok says.

The company is also working with partners on demonstrating the materials in applications such as sports equipment.

Working toward an rCFRTP bicycle frame

For example, Spiral RTC has spent about 2 years collaborating with Witcom and bicycle frame manufacturer  (Herent, Belgium) to produce prototype rCFRTP bicycle components.

“The bicycle industry produces a lot of waste in manufacturing, so we wanted to find solutions for reusing our own scrap in new parts, but we also needed this solution to be cost-effective and able to meet industry standards and our manufacturing volumes,” explains Juan Geerts, materials research engineer at Rein4ced.

He adds that the company had worked with other recycling companies before, “but they sent back essential thermoset composite dust, not a material we could work with.”

When designing a demonstrator project with Spiral RTC, Rein4ced decided to start with a bicycle frame component, with the goal of working toward development of a full frame. Spiral RTC and Witcom collaborated to create custom pellet material that met the performance requirements Rein4ced asked for. For this project, rCF/nylon continuous fiber tape scrap was recycled and combined with neat nylon to manufacture the new component.

“Now, we’re working on gathering data, not only [to determine] that the parts are up to standards but on their CO₂ footprint versus virgin carbon fiber,” Kok says.

Ultimately, the partners aim to produce a full, multi-material bicycle frame incorporating as much rCFRTP as possible. The next step is to complete a complex, full multi-material frame with Rein4ced by 2026. The part produced so far is said to have very close to virgin properties, and as long of fibers as possible.

Market competitiveness: Cost and carbon footprint

How do these materials compete in the market in terms of price and environmental impact?

“Today, recycled materials in general are at a similar price level as virgin materials, but have a significantly lower carbon footprint,” Kok says. He adds that he sees rCF as a solution for projected carbon fiber supply chain shortages in future as well.

How do the recycled materials compare to virgin materials in terms of carbon footprint? This is data that the Spiral RTC team is working on, and have recently performed a life cycle analysis (LCA) with the TPRC and DLR Institute of Lightweight Systems (Braunschweig, Germany).

According to , the LCA showed “significantly lower greenhouse gas impact compared to the production of virgin materials. Notably, the recycling process even has a lower environmental impact than the incineration of the same material.” Spiral RTC’s granulation process is also reported to consume 85% less energy than similar processes recorded in the databases of Sphera, the software suite used for the LCA.

“In general, we can say the [footprint] is an order of magnitude lower compared to virgin compounds. But there are, of course, variations depending on the material, and we don’t want to rely on assumptions,” Luinge adds.

According to Kok, you can recycle the injection molding compound a few times, increasing its attractiveness from a carbon footprint perspective. “Plus, compared to other recycling techniques, the energy needed for mechanical recycling is really low,” Kok says.

Transportation also plays a large role when determining the footprint of recycled materials. How far does the material need to be transported from the production facility to the recycler, then to the compounder, then to the end user? “This type of ecosystem only works in a local model, so right now we’re operating in the Netherlands and surrounding European region. Once we prove out this facility, we have ideas for expanding to build sites in other regions, such as in the U.S.,” Kok says.

Scaling up and building a circular economy ecosystem

“We are ready to scale up. The technology is here, but what does it take to get to the next step?” Luinge says. “There have been a lot of great demonstrators, but how do you make it widely adopted, a broadly implemented recycling route?”

The biggest challenge lies less in the technology itself, but in the collaborative ecosystem needed to make TPC recycling really happen at industry scale. A large part of Spiral RTC’s role is in trying to build this ecosystem, aligning both upstream waste sources and downstream applications of the recycled materials.

As Kok explains, a lot of companies supplying prepreg waste expect the composites recycling system to be more mature than it currently is, anticipating payments and steady supply and demand rates. “We are working toward these things, of course, but the waste material only has value once it’s been made into a new application, and the ecosystem is still being built up to mature the whole value chain,” Kok says.

He emphasizes, “We need parties who are willing to really make the next steps toward a more circular economy. Governments can force that, and some will, but it’s better if the motivation comes from the industry itself, from the companies and consumers. This is the real challenge. A lot of people say they want to do recycling, but we need to turn enthusiasm into action.”