Waste Tires Emerge As Important Plastics Ingredient

Use of highly processed tire waste in plastic compounds is growing 75% to 100% a year because the materials can replace more expensive plastic without compromising mechanical properties, says Bill Schreiber, technical director of plastics for Lehigh Technologies (Tucker GA).

Use of micronized tire waste is growing rapidly in plastic compounds.

“Business is going crazy right now because the micronized rubber powders help reduce costs,” Schreiber said in an interview. The pace of phone calls to Schreiber’s office increased when polypropylene and polyol prices jumped earlier this year. The list price for a 400 micron rubber powder is 25 cents per pound compared to $1.20 per pound for a specific type of polypropylene. Use of mineral fillers would reduce costs, but would also reduce mechanical properties of the compounds.

Schreiber says there is significant intellectual property involved in retaining rubber properties in the reprocessed powders. The preferred “feedstock” is waste truck tread because of its high quality. Lehigh Technologies then uses a patented cryogenic process to freeze the scrap, which is then resized in mills. Critical factors include consistent size and shape of the particles, which can be compatabilized for use in polyolefins, nylons, polyesters and polyurethanes.  Compatabilization creates a chemical bond between the rubber and the plastic.

The micronized rubber powder is called MicroDyne. Schreiber says they can improve the tensile strength, flexural modulus, and impact properties of recycled plastics, and avoid loss of mechanical properties with virgin plastics. Loadings range from 5 to 50%.

Injection molders can add the rubber powder using press side feeders.

He said that more than a million parts made from MicroDyne compounds are on the road, primarily in components that reduce the vibration in exterior mirrors. He said there is also significant potential to use the material in polyurethane foam in car seating.

The rubber particles can help offset rising polyol costs while also helping auto manufacturers achieve environmental goals. According to Lehigh Technologies, every pound of its micronized rubber powder saves nearly a gallon of oil and keeps tires and other post-industrial waste from going to landfills.

The company last year increased its plant capacity to 140 million pounds. The project included increased capability for pre-processing and material handling, micronized rubber powder classification systems, engineering enhancements on six production lines as well as the installation of state-of-the-art monitoring for process and quality control.

“These investments show our ongoing commitment to becoming the largest and most technically advanced supplier of micronized rubber powder in the industry,” said Alan Barton, chief executive officer of Lehigh Technologies.

Dave Petroni, vice president of operations for Lehigh Technologies said, “our production volumes have been growing rapidly over the past three years and at the same time we have expanded our product line to include a broader range of micronized rubber powders, such as nitrile, butyl and natural rubber.”

Markets for the micronized rubber include asphalt, construction, consumer goods, coatings, industrial rubber, plastics and tires. Powders come in a range of mesh/micron particle sizes – from 40 mesh (400 microns) to 300 mesh (50 microns).

Lehigh Technologies was founded in 2003 and is financially supported by by Kleiner Perkins Caufield & Byers, Index Ventures and NGP Energy Technology Partners.

Look for more technology advances to come. Last year, Lehigh Technologies and Dow Chemical announced a partnership to combine proprietary technologies to modify the rubber particles to make them even more useful.

“Our primary customer base, the world’s leading tire companies, has been requesting advanced technologies to enable increased sustainable content in tires.  The Dow-Lehigh research program is part of a broader technology program at Lehigh, aimed at providing sustainable solutions without compromise,” said Dr. Barton. “Our objective is to have one billion tires on the road manufactured with our alternative material – our collaboration with Dow is a critical step in realizing this significant milestone.”


About Doug Smock

Former Chief Editor at Plastics World and Senior Technical Editor Design News
Automotive, Composites, Construction, Filler, Green, Industrial, Injection Molding, North America

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