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Making quality products from rubber residues

06 November 2012

Rubber residues have long been recycled into products such as floor coverings and safety crashpads; now, for the first time, it can also be processed into high-quality plastics.

Rubber residues can be used in a variety of ways in high-quality materials (photo courtesy of Fraunhofer UMSICHT)
Rubber residues can be used in a variety of ways in high-quality materials (photo courtesy of Fraunhofer UMSICHT)

Each year throughout the world, up to 22 million tons of rubber are processed and a large proportion of it goes into the production of vehicle tyres. Once the products reach the end of their useful life, they typically land in the incinerator. At best, the waste rubber is recycled into secondary products. Ground to powder, the residues are used in the manufacture of floor coverings and doormats.

Hitherto, techniques for producing high-quality materials from these recyclables did not exist. However, researchers at the Fraunhofer Institute for Environmental, Safety and Energy Technology (UMSICHT) in Oberhausen have developed a material that can be used to manufacture products like wheel and splashguard covers, handles, knobs and steerable castors.

The new plastic compounds - elastomer powder modified thermoplastics (EPMT) - comprise powdered rubber residues blended with thermoplastics. Shredded rubber pieces are granulated to 3mm size particles, which are subsequently cooled with liquid nitrogen and then ground into an elastomeric powder. The powder is introduced to the melt-mix process with the thermoplastic (polypropylene) and additives. 

EPMT may contain up to 80 percent residual rubber; only 20 percent is made up by the thermoplastic. It can be easily  processed in injection moulding and extrusion machines, and products made from EPMT are themselves recyclable. Moreover, physical properties such as elasticity, breaking strain and hardness – can be individually modified, according to the customer’s needs. The researchers are presently able to process some 100 to 350kg of EPMT per hour.

Nike tests EPMT
In the “Re-use a Shoe” project, sportswear manufacturer Nike has been collecting used sneakers for a while now, recycling their soles and reprocessing them (under the Nike Grind brand) as filler material for sports arenas and running track surfaces. EPMT compound is now enabling Nike to place new products on the market.

As one of its official promotional partners, 'Tim Green Gifts' created  the first EPMT-based promotional articles under the Nike Grind brand, like frisbees, shoehorns and boomerangs. Discussions about using new EPMT compounds in the original portfolio, such as zippers, bag bases and sports equipment, have also been initiated. 

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