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Polyurethane saves weight in shoes

Walking on air

Test marathon: A sole clamped in this machine is flexed 100,000 times in order to test its resistance to cracking.

The average person buys five pairs of shoes every year. When choosing a pair of shoes, their weight should be just as important as their design. Plastics experts at Bayer MaterialScience have now developed a new plastic that turns heavy "clodhoppers" into footwear which is light as a feather. Because when it comes to walking and sports shoes, it is crucial to save as much weight as possible.

Polyurethane foam for lightweight basketball shoes

Nowadays light elastic polyurethane midsoles are used as standard in sports shoes. But in order to reduce the weight of basketball boots and work shoes even further, isocyanates and polyols – the liquid starting materials of polyurethane – are placed under several atmospheres of pressure in the mixing machines. This allows a large quantity of gas to dissolve in the chemicals. Under normal pressure the gas separates again from the viscous liquid and forms micro-bubbles. The resulting foam is less dense and altogether lighter. Read the article (PDF file) below to find out what cake mixture has in common with the soles of modern jogging shoes.