BASF polymer brings better bounce to runners’ steps

Running enthusiasts may enjoy what some call a runner’s high, but that euphoric effect can be tempered by pain from the pounding on their feet. A new polymer developed by BASF (Ludwigshafen, Germany) for running shoes aims to improve comfort while also conserving a runner’s energy.

The polymer is a new blend of Elastopan, a polyurethane material used in running shoe midsoles. BASF developed the new material for Brooks, a maker of running shoes and apparel based in Seattle, to address runner concerns about weight, comfort, durability and stability. Polyurethane is suitable for high-impact applications, including running shoes, because the material is versatile, said Chau Nguyen, footwear market manager for BASF in North America based in Wyandotte, MI. Just as important, polyurethane can take the pounding of millions of steps with very little degradation, he added.

“Brooks was able to give us a clear target, and we developed a high-performance elastomer for them using purer ingredients for superior performance and longevity,” Nguyen said.

Some midsoles are made from materials such as ethylene vinyl acetate (EVA), a copolymer valued for its flexibility and toughness; in running shoes, the material also provides a strong energy return. Brooks’ own research into runner preferences found many runners want a shoe that offers a “more responsive and springy ride.” But that research also uncovered concerns that a high-energy-return midsole could sacrifice performance or stability.

BASF developed the new Elastopan blend by making modifications at the molecular level, changes that the company said improved the material’s performance and longevity. Designed to better cushion a runner’s foot, the material expands under the foot with each stride. That expansion returns more energy from the force that is applied to it, which means that runners need to expend less energy. For every foot pound of force, Brooks says tests showed that the polyurethane midsole returns 72% of the energy. That’s 5% more than BioMoGo DNA, a different cushioning system available in Brooks running shoes. The new Elastopan blend is now available in Brooks’ Levitate line of running shoes.