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.”