Polestar 5 takes aesthetics and circularity approach to biocomposite seatback design

Adoption of recycled and recyclable materials within automotive design continues to grow in importance for automakers — especially in Europe, where proposed legislation sets requirements for recycled plastic content and design for dismantling and reuse.

Electric vehicle (EV) manufacturer Polestar (Gothenburg, Sweden) is one company that has been working on developments in sustainable materials for years, culminating in its current Polestar 5 vehicle which features more interior recycled, thermoplastic, mono-material and bio-based components than any of its predecessors — including, notably, several innovative flax fiber composite parts made in partnership with supplier Bcomp Ltd. (Fribourg, Switzerland).

Polestar is known for its EVs today, but got its start as a racing team in the 1990s modifying Volvo (Gothenburg) cars. In the early 2000s, the team became Volvo’s official performance car partner, started working on road versions of its racing cars and was ultimately acquired by Volvo in 2015 with a new focus on hybrid and electric road vehicles. Polestar was spun off as its own entity in 2017 alongside the launch of its first production vehicle Polestar 1, with Volvo retaining a share of the company and Volvo’s parent company, Geely Holding Group (Hangzhou, China), owning a majority stake.

Polestar’s relationship with high-performance flax materials supplier Bcomp goes back to the EV manufacturer’s Volvo days. “The relationship started when [Polestar founder and former CEO] Thomas Ingenlath and I were both working at Volvo, working on what would later become Polestar’s first vehicle,” explains Per Mårtensson, chief revenue officer at Bcomp. “I was working on the composite structure, and he was driving the idea of the concept coupe, and this became the flagship for the brand Polestar.”

By 2018, Mårtensson had been recruited by Bcomp to support business development and sales for the startup’s flax materials. At this point, Polestar was operating as its own company and assessing its approach for future vehicle development. “[Polestar] had this idea of developing the most sustainable EV,” Mårtensson says. “They weren’t only looking at the fact that it’s powered by a battery and saying that was enough, but actually taking a holistic view of the car and all of its components and trying to get as close to a zero-emissions vehicle as possible.”

“Nothing is undesigned. Nothing is in the vehicle without purpose,” explains Maria Uggla, head of CMF (color, material and finish) design at Polestar. “We are always trying to understand the impact of the materials we use — do we need all of these different polymers in the vehicle, for example, or can we try to make it as few as possible? Then for the ones we use, what should they be, what has the lowest impact and how do we create our interior in as smart a way as possible?”

This design philosophy is two-fold: Designing for recyclability at the car’s end of life (EOL), but also designing with low-carbon or circular materials to begin with.

“A lot of things are recyclable on most cars, which looks great on paper, but that only works out if they’re actually recycled in the end,” Mårtensson points out. “If you use as much circular material [like natural fibers] as possible within the vehicle, then at the very least you’re trapping the CO₂ and boxing it into these materials. If you use synthetic materials that you can’t recuperate energy from, then all you can do is try to compensate for the CO₂ that was emitted.”

He continues, “Bcomp, of course, is focusing very hard on providing sustainable and circular solutions for the automotive industry. So in 2018, [Ingenlath and I] met up again, and the fit between the two companies was there.”

Developing a Polestar-specific flax fabric

“We [Polestar] were looking for materials that were lightweight and high-performance but also something more innovative in terms of the design,” Uggla explains. “And in terms of sustainability, it needed to be the real deal. That was very important. There are so many ways to fake it and greenwash it and make things that look sustainable but in the end don’t add any benefit.”

Up to that point, Bcomp’s signature ampliTex woven fabric and lattice-like powerRibs flax fiber/epoxy products had been demonstrated in a variety of motorsports and performance sporting goods applications, but they had not yet broken into higher-volume production applications such as automotive.

Mårtensson says there was a lot of reason to believe these materials would be a good fit for automotive — and they have, today, been used on several prototype and production automotive platforms: They can be manufactured in a one-step compression molding process, contribute a unique design and provide both lightweighting and performance potential to the overall vehicle.

“We were interested in using bio-based composites and we were also interested in Bcomp’s background in high-performance applications, so we started taking a look at the materials and trying to understand how we could use them in our vehicles,” Uggla says. From a designer’s perspective, though, “I saw immediately that we needed to do something with the material’s design. It would not fit in a Polestar vehicle the way that it looked. We needed to do our own take on the material.” This was important because one of the goals was to find a bio-based material that could be used in visible as well as structural applications within a vehicle.

Bcomp’s original ampliTex high-performance fabrics had been designed to mimic the weaving patterns of a carbon fiber fabric — something familiar to motorsports and performance sports customers. “Polestar wanted the performance that the material offered, but wanted it to not look like carbon fiber — it needed to look unique and high-tech and to match their style. But of course, without losing the performance or environmental benefits. It needed to incorporate ‘sustainable performance,’ which became something of a tagline for us during this project. It was an interesting challenge,” Mårtensson says.

The two teams began sending designs and eventually sample materials back and forth, trying out different weaving techniques, colors and patterns. “All of our interiors are dark, so we knew we wanted it to be charcoal, but we also wanted to play with different lines and patterns,” Uggla says.

Uggla and her team spent two days with Bcomp trialing about 100 different fabric samples with a variety of binders. The top designs were brought back to Polestar’s offices in Sweden to be pressed with polypropylene (PP) films into demonstrator components that would be tested and trialed.

“The material didn’t just look good, it was also performing really well,” she emphasizes. “This has helped the panels to be extra strong and rigid. We also did an LCA [life cycle assessment] calculation and compared to a seatback in ABS with adhesive and PVC — the flax fiber/PP version lowered the emissions by half, but it also lowered the weight and only required around half the use of plastic.”

The Precept: Thermoplastic/flax fiber seatback

These trials ultimately fed into the development of the Precept concept vehicle, Polestar’s battery-electric four-door sedan announced in 2020. For this concept, both exterior and interior components were trialed using natural fiber composites, including a seatback made using ampliTex reinforced with powerRibs, as well as powerRibs on the exterior trunk trim and interior side console.

One of the most visible of these is the seatback for both front passenger seats. This shell-like component serves as support for the passenger’s back — both in terms of safety and comfort — and connects the upper and lower portions of the seat.

The compression molded part combines three reinforcements: an outer, high-performance layer of ampliTex fabric made using Polestar’s signature charcoal color and what Uggla describes as a crepe weave; an internal core of traditional natural fiber polypropylene (NFPP) board (a compression molded flax fiber nonwoven combined with PP); and a layer of powerRibs where needed for additional support and stiffness and to keep the panel as thin and light as possible. These are laid up in the mold with layers of PP films, and pressed in a one-step process. In the production vehicle, attachment points are injection overmolded in PP onto the finished seatback.

Why PP? Polestar and Bcomp knew that a thermoplastic would offer the best recyclability scenario. “Of these, the manufacture of PP has the lowest emissions,” Uggla says.

“If you go down to the material level, the seatback is all one material. It’s flax fiber and PP, all of it,” Martensson says. “You’re using different physical shapes, but everything is the same material, which means you can more or less mill it down into an injection moldable material at its end of life.”

The design also had to match the overall look of the vehicle, which, Uggla explains, was based on three images. “One was a very high-tech, lightweight tent. Another was a leaf with veins. And the third was a knitted sneaker. Those are three quite odd images that became the flare of the concept car.”

The seatback design was inspired by the leaf image. “The powerRib technique evokes the veins of a leaf, and they give structure to the part the way veins do for leaves,” Uggla says.

Unfortunately, the placement of the ribs makes them invisible once the full seat is assembled. So, for the Precept’s unveiling, the team had the idea to make them visible through the placement of backlighting installed inside the seat. “We loved this, and ended up putting this backlighting throughout the vehicle in various places,” Uggla recalls.

Moving into production: The Polestar 5

As Polestar began to look forward into which elements of the Precept to carry over into future production vehicle designs, the company decided to pursue interior flax fiber/PP components, at least for the first production version. “From a market-readiness and pricing perspective for where we were with flax fiber composites 5 years ago, this made sense to start with the simpler, interior parts,” Mårtensson says. “We as an industry are a lot more mature today when it comes to use and expertise in these materials for exterior applications.”

Polestar has strived to make each progressive model year of its production cars more and more sustainable over time, Uggla adds. “With the Polestar 3, we began using recycled materials for as many places as we could — for example, the carpets in our vehicles are now made from 100% recycled material. With the Polestar 4, we expanded this, and began developing mono-material parts that are more easily recyclable.” The Polestar 4, for example, includes interior door panels made from NFPP boards combined with PP components.

“For the Polestar 5, we went even further, and this time, following up on the Precept, we wanted to focus on light weight and use more biocomposite materials, also displayed on certain components, as an important part of the design,” Uggla says.

The Polestar 5 includes several components made using material from Bcomp, including two seatbacks, the interior trunk lid, trunk header and the two sides of the console.

The car also incorporates additional NFPP materials, bio-based vinyl and recycled textile or aluminum in areas where possible. “We’re constantly pushing our suppliers and trying to make them come up with more innovative solutions,” Uggla says. This extends beyond materials and part design, as well — the company sets strict guidelines for its own facilities for reduced energy consumption, proper waste removal and recycling, and low-emissions shipping of its products. It also asks its suppliers and partners to abide by its sustainability standards.

Aesthetically, the backlit, leaf-inspired design from the Precept inspired the production seatback design. “The light gray, very thin yarns that we have added really mimic the light soaring through the material that they did on the Precept,” Mårtensson says. “You have so many advantages with it. It looks good and also performs well. It reduces the material you put into the car. And by that, you are also increasing range. I mean, there’s a limit to the impact — it’s only a seatback — but imagine if you take this approach everywhere in the vehicle.”

Use of these materials also saved about 7 kilograms of weight on the seatback compared to an all-plastic version.

The 2026-MY Polestar 5 launched in the European market in late 2025. From here, Polestar and Bcomp continue to work together on next-generation ideas.

Uggla says, “I believe that it’s every modern company’s responsibility to take accountability for the materials used in their products, and to understand that you do have to have material that has already been extracted. In the best scenario, we would have a much more closed loop with the material in the car, so that the material we put in comes from other cars. We take steps forward with each vehicle we make.”