New composite materials for sports shoes that run into the future
The collaboration between Covestro and Anta Sports (a company that brings together prestigious sportswear brands) has given birth to a new basketball shoe tested by NBA all-star Klay Thompson.
This sports shoes are designed for sport but since the mid-1980s they have forcefully entered everyday life. We ask for everything from our shoes: greater comfort and design but also to represent our imagination and our dreams. No shoe in the world has become more iconic than the gym one, created for the sports fields of various disciplines but soon passed into the wardrobe with all its cultural references.
Sports shoes with a carbon fibre core
Anyone who has seen The Last Dance series, about the life of legendary basketball player Michael Jordan, will have noticed the laborious work of bandaging the ankles before each game. The reason is that when 2-meter athletes move at great speed in a space that is just 28 meters long, the strain on the ankle is enormous.
So sports shoes must meet criteria that prevent injuries. An extremely technical and invisible component of the shoe which is called cambriglione (shank in English) plays a very important role. It is a reinforcement inserted between the heel and the sole to have the right mix of stiffness and elasticity, hardness and softness that avoids excessive rotations of the foot and supports it.
There are even European standards that regulate the performance of the shank, which is usually made of metal. In the Covestro laboratories, it was possible to use the carbon fibre composite material to build a very thin one. The performance is so high that it meets the needs of a high-impact pitch such as basketball.
Technology and design: the perfect combination of iconic sneakers
A quality sports shoe is a technological concentrate made of research and innovative materials in every component. If at first sight the colours and the shape are striking, each part must be designed to withstand specific stresses and give protection, support and elasticity. Covestro's polymer materials offer innovative, beautiful and sustainable sports shoes solutions.
Thermoplastic polyurethane for the upper
By upper we mean the upper part that wraps the foot. In sport's shoes, leather has been replaced by fabric: softer, more elastic and enveloping. From the canvas of the shoes of the 50s-70s, we have moved on to the thermoplastic polyurethane mesh fabric that offers resistance but also softness and therefore comfort. In shoes intended for outdoor use, the fabric is waterproofed with a water-based, ecological and non-polluting polyurethane coating.
Sustainable TPU for the midsole
The midsole is located between the sole and the foot. It is a fundamental part because it is this that must give flexibility and cushion but also a certain return of the kinetic energy of the movement. It must be soft and resistant at the same time, with high resistance to tearing and abrasion. In Anta Sports sport shoes the midsole is produced using TPU (thermoplastic polyurethane) powder printed with the SLS (Selective Laser Sintering) process which allows precision but above all the recovery of unused powder that can be recycled later.
H3: Viscoelastic polyurethane foam for the lining
The lining is the inside of the shoe. In sport's shoes, a well-designed lining helps relieve foot fatigue and provide greater comfort. The solution adopted is a viscoelastic polyurethane foam because it has high energy absorption and impact resistance properties.
Cambriglione (shank) in carbon fibre
We can define it as the secret heart of a shoe. Essential and invisible. For the new basketball sneakers, Covestro, together with the Anta specialists, have created a core in precious carbon fibre with a thickness of only 1 millimetre.
Carbon fibre reinforced thermoplastic composites have a valid use in many applications. The combination of the strength and resistance given by carbon fibres together with the flexibility of thermoplastics creates a material that is ductile in design but strong and durable.
The unidirectional (UD) composite tapes obtained by Covestro are only 120 microns thick. They can be laminated together with different angles to obtain sheets characterized by performance designed for individual fields of application:
from automotive to clothing, from the aviation industry to consumer electronics.
The lamination process allows to obtain a material that has:
The modelling flexibility of a plastic material
The weight reduced even by half compared to aluminium
The resistance tripled compared to steel.
Carbon fibre composite materials, rigid and torsion-resistant, are a true technological innovation in sport's shoes.
The numbers and production challenges of sports shoe
Market research from Global Info Research found that the industry had totalled approximately $ 70 billion in 2019. Forecasts are for an annual growth rate of 6.5%, thus exceeding 100 billion in 2024.
Sports shoes, from the time of the legendary Air Jordan, have become a real mass phenomenon and meet the more informal lifestyles that are emerging. No other item of clothing has become a social and cultural sign like this.
Companies are looking for ever greater quality and scale production capabilities. And together they want to have a careful look at sustainability and the recovery of materials for the increasing success of these issues with consumers.
Covestro plastics and composites can be thermoformed efficiently with high yield rates and reduced production cycle times, thus achieving cost rationalization. The recyclability of the material, thanks to its thermoplastic matrix, offers added value for footwear brands that want to focus more on sustainability.
Lisa Ketelsen, Head of Covestro's Thermoplastic Composites Business, says:
“We are very excited to support the companies in the design and development of athletic shoes by contributing our expertise in composite materials. We see them as materials that enable efficient mass production for high-performance components in a wide range of applications, including footwear. Another advantage is that composites can be tailored to the desired performance and different production sizes and offer great value creation across all industries.