New technique allows scrap rubber to be recycled into high-quality plastic
By Paul Ridden
November 13, 2012
It's reckoned that most of the 22 million tons of rubber that is processed every year worldwide goes into making vehicle tires and that once rubber products reach the end of their useful lives, for the most part they end up being incinerated. Even when the rubber residues are reclaimed and re-used to make new products, the lack of techniques for producing high-quality materials means that the recyclables are relegated to secondary products such as arena or playground floor coverings or padded doormats. Looking for new ways to optimize the recycling of rubber waste, researchers have developed a material called EPMT that has the desired material properties and characteristics for use in the manufacture of high quality products such as wheel and splashguard covers, handles, knobs and steerable casters.
Holger Wack, Damian Hintemann and Nina Kloster from the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT in Oberhausen, Germany, have so far developed three basic elastomer powder modified thermoplastics (EPMT) recipes and have formed a new company named RUHR Compounds to bring EPMT to market. The company is also offering custom services which examine where EPMT can be used to replace existing materials in customer product ranges and then come up with special recipes to match specific requirements.
Machines currently used by the researchers are capable of producing up to 350 kg (770 pounds) of EPMT every hour and individual material properties like elasticity, breaking strain and hardness can be modified according to the need of the customer.
"In the first step, the rubber residues – that can be meter-long rubber pieces are granulated to three-millimeter large particles," explained Dr. Wack. "The particles are cooled with liquid nitrogen and then ground into elastomeric powders. This is then conducted to the melt-mix process with thermoplastics and additives. Here we use, for example, polypropylene as a thermoplastic material."
The new compounds can contain up to 80 percent residual rubber and the researchers claim that EPMT can be easily processed in injection molding and extrusion machines. EPMT used in the manufacture of new products can itself be recycled again when those products reach the end of their useful life.
For almost ten years, sporting manufacturer Nike has been collecting used sneakers under its "Re-use a Shoe" program and recycling the soles as filler material for arenas and running tracks under the "Nike Grind" label. The company is now working with the Fraunhofer researchers to place new EPMT-based products on the market, with the first promotional items already available from Tim Green Gifts.
Source: Fraunhofer (UMSICHT)