Every end-of-life car is a source of raw materials - in theory anyway. (Credit: Image courtesy of Fraunhofer-Gesellschaft)

ScienceDaily (Nov. 10, 2007) — Once plastics have been built into a car, they are rarely recycled. Compressed into granulate material, the shredded plastic parts are usually too indiscriminately mixed to permit any further use. Researchers have now found a way of separating the different types of plastic.

Every end-of-life car is a source of raw materials - in theory anyway. In practice, however, these resources are still used far too seldom - particularly where plastics are concerned. During the recycling process, the polymers land in the non-metallic shredder residue along with dust, slivers of metal and textile fluff, and are made into granulate using the SiCon process. This mixes the plastics so indiscriminately that it has never yet been possible to separate them into the individual types again. They are normally used as reducers in blast furnaces.

In future, this granulated plastic could be salvaged and transformed once again into dashboards and other car parts. In a joint project with Toyota and Sicon, researchers at the Fraunhofer Institute for Process Engineering and Packaging IVV in Freising have laid the foundations with CreaSolv®. ''We developed a special solvent that removes a particular type of plastic from the granulate: the polyolefins used to make air filter housings, shock absorbers and side panels,'' says IVV project manager Dr. Martin Schlummer.


''While this type of polymer dissolves in the solvent, the other plastics remain in the granulate.'' The solvent is separated from the polyolefin and re-used. There is a further advantage, too: The CreaSolv® process is so effective as a cleaner that scientists can also separate out any toxins with which the polymer may have come into contact during shredding. ''Using this technology, the overall recycling rate for end-of-life cars - metals, plastics and textiles - can be increased to over 90 percent,'' says Schlummer.

The researchers have already been using the idea behind CreaSolv® for about a year, with great success, to recover styrene copolymers from electrical appliances such as computers and TVs. In this way, the researchers can recycle about 50 percent of the high plastic content in discarded electrical appliances. Nevertheless, a great deal of development effort was necessary before it was possible to process the plastics from cars as well. ''Different polymers are used in cars than in electrical appliances, so we had to develop completely different solvents,'' the expert explains.


The researchers have already put the basic process into practice. In future, they intend to recycle other types of plastic from cars in addition to the polyolefins - perhaps by combining the methods for recovering styrene copolymers and polyolefins. Eventually, Schlummer hopes, it will be possible to make optimum use even of plastics from shredding plants where refrigerators, kitchen ranges and cars are all shredded together.

Adapted from materials provided by Fraunhofer-Gesellschaft.