Engineering a Rock-Solid Plan for Recycling Plastics

08/03/2007
By Used with permission from Mass High Tech By Jay Rizoli

Engineering ߞ; be it chemical, civil, electrical, mechanical or other ߞ; addresses the composition, design, manufacturing and operational applications of the science.

But when the discipline is plastics engineering, there’s also the matter of what to do with one of the world’s most ubiquitous and practical substances once its primary use is over.

At the University of Massachusetts at Lowell, which has the largest, most established and only accredited plastics engineering program in the United States, that area of study falls to Robert A. Malloy, whose focus includes plastics product design, polymer processing, polymer process instrumentation, applied polymer rheology and, of course, recycling of plastics materials.

Malloy, along with several students and civil engineers at Tufts University, has developed a cinder block composed of 20 percent recycled plastic and 80 percent ash from coal-fired power plants. The concept emerged five years ago, and the trial production run of blocks occurred last year.

“A cinder block has three components ߞ; aggregate, sand and cement,” Malloy said. “We’re replacing the rock portion with fly ash and plastic.”

That idea was initiated, Malloy said, by Christopher Swan, an assistant professor of civil and environmental engineering at Tufts, who was investigating the reuse of hazardous and nonhazardous waste materials for construction.

“He came to us with the ash idea but didn’t have the plastics knowledge,” Malloy said.

The melted plastic combined with the ash is formed into a solid block, then ground into small chips called synthetic lightweight aggregate. That material is sent to a manufacturer, in this case Camosse Masonry Supply Inc. in Worcester, to be combined with sand and cement formed into a lighter-weight commercial building material.

“The 20 percent-80 percent mix is the best balance of properties,” Malloy said. “Obviously the more plastic there is, the more flexible it’s going to be. The plastic is the glue that holds it together, and the properties are determined by the percentage that’s in it.”

Next up is a patent, for which the department applied last year and hopes will be granted within a year. Following that, they hope for a possible sale of the technology, “if we were able to supply the aggregate at a competitive price,” Malloy said. “It could be a waste management company that wants to pursue it, or a utility company that has the ash.”

Whatever the case, disposal costs for coal ash are steep, and paying a fraction of the current cost to a plant that will reuse the waste should be appealing.

“What we’re doing is taking on and making a product from two waste streams, both of which are currently going to landfills,” Malloy said.

Another upside to the cinder block project is that it has helped generate enough interest in plastics recycling to prompt the construction of a lab facility for research and education in recycling, as well as helped garner corporate dollars to do so.

“One of the things about this program is that we are so focused, and our students and alumni so close-knit, that they support our program,” Malloy said.

And it increases focus on the plastics engineering department in general, which teaches a growing and evolving science that is truly vast in scope.

“The department is focused on technology for people who design plastics, companies like Boston Scientific,” Malloy said. “There are thousands of different kinds of plastics, and it’s like mechanical engineering, but unlike a mechanical engineer our students take a lot more chemistry.

“It’s almost like being a metallurgist only with plastics, and there’s a lot more to know.”