When performance counts, biobased materials deliver

Sebastien-Jun Mougnier, sports market development manager at France-based specialty chemical company Arkema would like to correct a misunderstanding. Contrary to what is often believed, bio-based, high-performance materials for sports applications are just as good, or sometimes often better than conventional products. He should know: Arkema has been producing them for decades.

Bio-based materials, said Mougnier during a recent webinar, are materials that are bio-sourced, or in other words, made from renewable sources. “Bio-based materials are not all biodegradable and ours are not, but as thermoplastics they are recyclable” he stressed.

The bio-based trend is a logical development in light of the push towards improved sustainability, leading to a more eco-friendly approach to innovation, as consumers look for responsible sports products that also provide the quality they are used to.

Bio-based materials meet these requirements, and can deliver performance that is equal or even superior to conventional materials. “In my opinion, this combination of performance and low environmental impact is a winning one, now and for the future,” said Mougnier.

The sustainability trend in sports is visible in various ways. In the outdoor market, he noted that brands were increasingly using recycled polyesters, recycled nylons or even bio-based materials in an effort to produce more ecologically responsible products.

Footwear is another area where sustainability has taken hold. A well-known example is Parley and adidas: on Earth Day in 2015, Parley first announced its partnership with adidas. In the five years since, the brand has worked on phasing out single-use plastics and microbeads and launched entire product lines. The Parley shoe, for example,  uses materials based on recycled plastic bottles for the upper. New brands, such as Veja or AllBirds – have introduced shoes made from recycled materials, biobased materials, or even both.

Winter sports equipment is a third area where biobased materials have gained a foothold.

Renewably-sourced materials have been used for a number of years already to produce high-end ski boots.

Performance is key

“What’s interesting is how the message has changed,” said Mougnier. “Yes, sustainability as a topic is becoming more and more important, but in a product, it’s performance that counts.”

Performance materials that are biobased can deliver results that are just as good or better than conventional materials, he added. “Arkema has two product lines that fall into that category: Pebax Rnew materials, high-performance thermoplastic elastomers, and Rilsan polyamide 11 polymers – each range designed for extreme lightness, energy return, fatigue resistance, and durability.”

“PEBAX®, RNEW® and RILSAN® are all registered trademarks belonging to ARKEMA,” he added.

Arkema’s biobased materials are made from on castor oil, which is derived from the seeds of the hardy, drought-resistant castor plant. Castor oil is an ingredient used in pharmaceuticals and cosmetics, but not food. No GMOs are used. The castor oil is used to produce amino 11, which is then polymerised into 100% biobased Rilsan polyamide11. The same monomer is also used to produce the partially biobased high-performance TPE, Pebax Rnew range, which has a bio-content of between 30% and 97%.

“The Pebax Rnew material is a copolymer based on a rigid block and a soft block,” said Mougnier. “The soft block is based on polyether, while the rigid block is a long-chain polyamide. For Pebax Rnew products, we use biobased Rilsan polyamide 11 in the rigid block. So far, the soft block, the polyether, is not biobased.”

Arkema has been producing Rilsan resin for over 70 years and Pebax resin for some 40 years. In that period, the company has gained a wealth of experience and expertise in production optimisation and yield optimisation, as well as in the formulation and chemistry optimisation of the products to meet the challenging technical requirements of its customers, said Mougnier. “PEBAX®, RNEW® and RILSAN® are all registered trademarks belonging to ARKEMA,” he added.

As a result, they are available in a wide range of grades, with a bending modulus from very  flexible to very stiff - from 20 megapascal up to 20 gigapascal.

“We have a grade that is highly suitable for biobased, breathable, stretchable and waterproof membranes for sports. The soft grades can also be used to make biobased foams. Others are used for injection moulding, for the top skins on skis and snowboards, biobased yarns and even 100% biobased 3D printed sports components.”

However,  one of the first applications was in textiles, in the 1950s.        

“Now the bio aspect is becoming more and more important, we would like to re-explore this product: to see if we could bring something interesting in addition to the bio-aspect of our product,” said Mougnier.

Benefits of biobased – are they real?

“Yes,” said Mougnier. “One key factor is the lightness of the material. For example: Rilsan polyamide 11 resin is up 10 to 15% lighter than conventional nylon 6 or 66, so in Pebax materials, this can mean a 10-20% lighter material.” A lighter material means athletes use less energy, allowing them to reach a higher speed or maintain a high speed for a longer period of time.

Another factor is how the stiffness stability of the material is affected by moisture or temperature, an important consideration for sports gear, as conditions of moisture and temperature are very liable to change.

“In polyamide 11, the modulus is relatively stable - between 1.5 and 1.3 gigapascal - whereas with nylon 6, under the same conditions, this can fluctuate from 3.2 to 1.5 gigapascal – a huge jump.”

This same jump is seen in the glass or carbon-fibre reinforced nylon 6 grades compared to polyamide 11 compounds.

Obviously, the role of temperature is an important one for winter sports gear. “TPU and Pebax Rnew materials may have the same stiffness at room temperature, but at -30◦C, the modulus of the TPU increases significantly while the modulus of the Pebax TPE remains stable,” Mougnier pointed out.

Impact resistance is another area where polyamide 11 beats nylon 6 or polyamide 12, in addition to offering improved UV resistance and better chemical resistance compared to short-chain nylons.

Extruded polyamide 11 has long been used in top sheets for skis and snowboards, thanks to precisely these properties of low temperature performance, UV and scratch resistance - but also, said Mougnier, because it enables the use of dye-sublimation technique, “something ABS or TPU cannot handle”.

Yet the main reason Pebax Rnew material has proven to be immensely successful in applications such as high-performance sports shoes is because of its efficient energy return – or ‘snappiness’, as this is called. Its intrinsic energy loss during flexural cycling is extremely low, and it is maintained  over a wide temperature range. In other words, it does not become brittle or lose its elasticity.

“Especially in the softer range, there is a huge gap in terms of snappiness between the same TPU hardness and Pebax Rnew material,” Mougnier pointed out. “And this gap is also transferred to foam applications, as it is these grades that are usually used for foaming. It’s why we usually see a better rebound for Pebax TPE than for TPU.”

Obviously, biobased materials also offer benefits in terms of the environment. Compared to conventional, oil-based polyamide 12, the CO2 emissions per kg production of Rilsan polyamide 11 is 40% lower, while also obviously reducing our dependence on fossil fuel. For TPU versus Pebax Rnew material, again a 40% reduction in CO2 emissions is seen, on top of which the 20% difference in density between the two materials produces an even greater reduction in carbon footprint on a volumetric basis (and not by weight).

In addition, bio-based Pebax Rnew and Rilsan polyamide 11 resins also offer benefits in terms of, for example, recyclability. Unlike conventional PTFE membranes, Pebax Rnew membranes are nylon based and can be easily recycled. Unlike EVA foam, Pebax foam is not crosslinked, again, making it easily recyclable.

Additive manufacturing opens up new possibilities

Design freedom, a faster development process, an optimised output – these are just a few of the ways additive manufacturing is changing the sports world. Using additive manufacturing processes (3D printing), product designers take advantage of new materials and complex geometries that are impossible with traditional manufacturing methods, creating products that are stronger, or equally strong, while using less material.

Understanding the growing importance of this technology in sports, with its potential for functional rapid prototyping and completely customised equipment, Arkema has developed a polyamide 11 SLS (selective laser sintering) powder called Rilsan Invent Natural that can bring functionality into the product, said Mougnier.

“The elongation at break is much higher than for polyamide 12, and in terms of impact resistance, there’s no break even at -30 degrees C.”

The material is already being applied in the market. In the UK, a company called Hexr produces the first eco-bicycle helmet made using 3D printing, using Rilsan polyamide 11 SLS powder.

The polyamide 11 can replace the ePP or ePS foams in traditional helmets, using a honeycomb core that has been independently tested to be 26% safer than traditional foam helmets.

Because of its low density, polyamide 11 offers flexibility, ductility and impact resistance.

A 10-second head scan is taken of each customer, to ensure each helmet is precisely customised to each individual’s head shape, enhancing fit and comfort when wearing.

For the future

As the world’s leading producer of polyamide 11, Arkema is also working on projects aimed at boosting sustainability in the supply chain.  Together with BASF, Jayant Agro-organics and Solidaridad, Arkema founded Pragati, a sustainable castor initiative to enable sustainable castor bean farming in India. The goal of Pragati is to enhance castor productivity in India, where the majority of the world supply originates.

End-of-life is another area of attention. Today, Arkema produces high performance materials that are also biobased. In the future, the company will be working with customers both to design recyclable finished products and to recycle them.

Arkema’s new Virtucycle recycling program represents a virtuous cycle that enables customers to partner with Arkema in open-loop and closed-loop initiatives for post-industrial and post-consumer recycling projects for its specialty polymers.

“The objective is to regenerate the materials, not only to recycle them and this is what we are open for discussion with all direct and downstream customers - to close the loop in sports products,” said Mougnier.

So in the future, we will have high performance biobased materials that offer lightness, a high energy return, stiffness stability, a low carbon footprint - and we will help to recycle them.”