Of the nearly 300 million tires discarded in the United States each year, more than half end up either as landfill or are burned for fuel in cement kilns and in other industries.
Lehigh Technologies of Tucker, GA, has developed a process for rejuvenating discarded rubber that could open up new recycling opportunities. If the company's technology catches on, it could carve out a billion-dollar market for high-performance recycled rubber.
Used rubber is hard to recycle because it is vulcanized--hardened and rendered chemically inert--by the addition of sulfur and other compounds to the material's long molecular chains. Small chunks of used tires can be partially melted and used as filler in asphalt, but devulcanizing rubber involves expensive chemical and thermal processes.
Lehigh Technologies instead shatters rubber into a fine powder using a process that involves freezing old rubber and smashing it to pieces. This starts with tires that have been torn into half-inch chunks using conventional shredding equipment. Lehigh mixes these rubber pieces with liquid nitrogen, cryogenically cooling the rubber to -100°C. The rubber is then fed into a high speed "turbomill" that shatters it into particles no more than 180 microns in size.To read the full, original article click on this link: Technology Review: New Life for Old Tires
Author: Phil McKenna
