Concept Shoe Emphasizes ‘Green' Materials

At K 2010 held last month in Dusseldorf Germany, Bayer MaterialScience presented a concept for a new type of shoe.

The shoe features polymers made from renewable resources and demonstrates the potential for environmentally friendly materials in the shoe industry, a growing trend.

"Footwear manufacturers, end consumers and, not least, the environment can all benefit equally from this development," says John Zhang, head of Bayer MaterialScience's Global Footwear Competence Center in Shanghai, where the concept was developed.

The shoe cap used in the prototype of a safety shoe is made from a blend of corn-based polylactic acid and polycarbonate. It's also lighter than a conventional steel version. The material is engineered for special impact resistance and is recyclable.

Click here for larger image.

Thermoplastic polyurethane based on a high proportion of renewable raw materials are used in the concept shoe's heel counter, shoelace eyelets and the manufacturer's logo on the sole. The abrasion- and wear-resistant bio-based TPU can also be used for traditional TPU shoe components such as outsoles or decorative upper parts.

In microcellular polyurethane elastomer systems for outer soles and midsoles alone, the proportion of renewable raw materials is as high as 70 percent.

TPU films form a vapor-permeable membrane to reinforce the inner sole, without using plasticizers.

A counterfeit-proof label based on polycarbonate film is laser engraved.

The green shoe concept also offers health benefits for employees of shoe manufacturers. "The aqueous coating and adhesive products are completely solvent-free and, compared with conventional production, the polyurethane products used do not contain any heavy metals. This is also important for disposal, once a shoe has reached the end of its service life," says Dr. Zhang.

Bayer MaterialScience is also working on development of materials from straw and wood waste.

The Global Footwear Competence Center was opened in Shanghai by Bayer MaterialScience in response to the widespread movement of shoe manufacturing to China. Engineers from the Simple Factory Group in China participated in the collaboration.

Established in 2006, the Footwear Competence Center includes injection-molding machines for thermoset and thermoplastic polyurethane applications, casting machines as well as a pre-polymer and polyol formulation pilot plant.