The world is on the move. To keep physically fit, more and more people jog for miles, across fields and along roadways. You can go running just about anywhere. All you need is comfortable appareland a pair of running shoes. The global sports equipment industry is profiting from an increased enthusiasm for running: Worldwide, runners spend an estimated €15 billion on their equipment. Customers place top priority on good footwear. Even people who only go jogging occasionally now look for lightweight soles that provide optimal shock absorption and enhanced running comfort.
Today’s sports shoes are genuine high-tech products compared to previous versions: The many different materials used to manufacture the shoes make them lightweight and stable. These materials enable the shoes tobe tailored precisely to suite the style of running, the customer’s expectations and the various running disciplines. All this can be confirmed with a look around the development laboratories of sports shoe manufacturers: Test subjects run over sensitive pressure measuring plates which analyze and evaluate everystep. High-speed cameras film the movement patterns and the heel-to-toe motion of the feet in the tiniest detail. All this information goes into the subsequent shoe design, which enables athletes to achieve new personal bests – and also offers recreational runners optimal running conditions.
Manufacturers are permanently on the lookout for cutting edge technologies and innovative materials. adidas is alsoconstantly further developing its running shoes. The company, headquartered in Herzogenaurach, Germany, has been supported by BASF materials experts for more than 20 years. Using BASF’s new foam InfinergyTM, adidas has now developed the Energy Boost, a thoroughly new running shoe with unique spring and cushioning properties. Its outstanding feature is the midsole, the central element of every running shoe. It is made from a new particle foam which absorbs the shock impact on the foot during jogging, while simultaneously cushioning the foot. The high rebound effect of the material provides therunner with an energy return not offered by any other running shoe.
InfinergyTM is made of expanded thermo plastic polyurethane, in short E-TPU. “E-TPU is manufactured by foaming the starting material, TPU granules,” explains Dr. Uwe Keppeler, material and process developer at BASF. “After pretreatment with pressure and heat, the individual granules measuring up to five millimeters each are blown up like popcorn.” In the process, its volume increases tenfold to produce oval foam beads with tiny,closed gas bubbles inside. “These sealed air cells make the lightweight foam beads very elastic and provide the desired rebound effect. The individual beads can be imagined as being like tiny footballs: The more air they contain, the better they bounce and rebound back,” says BASF research scientist Dr. Frank Prissok.
Left：Cross section of a single foam bead: Thescanning electron microscope image shows tiny air bubbles (measuring 30 to 300microns) enclosed in the BASF plastic.
Right：Rebound effect material: 2,500 Infinergyfoam beads form the midsole of the new running shoe.
2,500 foam beads in one shoe
For every midsole, adidas needs about 2,500of these small beads. To convert them into the desired form, they are treated with hot steam, a process in which the out most layer of the beads melts slightly, causing them to bond into a stable shape. The internal air cell structure remains unaffected by this process.
A midsole made from Infinergy can be compressed to an extreme degree: by about half of its volume at a pressure of two bar. This property is particularly effective in absorbing the shock impact onthe foot. As soon as the compressive impulse subsides, the foam returns to its original shape at lightning speed. The sole therefore absorbs the runner’s energy, but then returns a large amount to the runner. This rebound elasticity of the individual Infinergy beads literally transforms the running shoes into energy stores: “When the foot is pushed off the ground, the force expended is largely returned to the athlete. This results in completely new and improved running behavior. Many runners have told us that the shoe feels like it is almost alive,”explains Gerd Manz, Senior Innovation Director Global Brands at adidas. Anotheradvantage of BASF’s specialty foam: It’s not only lightweight, but it also remains elastic over a wide temperature range. The particles make sure that the Energy Boost shoe also retains its positive properties at minus 20 degrees Celsius.“The running characteristics are therefore the same at frosty temperatures as at summer like30 degrees Celsius,” says Manz.
Join us at Chinaplas 2014 for more about InfinergyTM:
- Booth B41, Hall N1
- Shanghai New International Expo Center, 2345 Longyang Road
-9:30 - 17:30, April 23-26, 2014
We create chemistry for a sustainable future!
