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Material lighter than steel stronger than train - made of everyday plastics

Staff Writer |
Imagine a material lighter than steel, longer-lasting than lumber and strong enough to support 120-ton locomotives.

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Now imagine that material is made from milk containers, coffee cups and other plastics that we recycle.

It's called structural plastic lumber, and the ingenious, nontoxic material was invented by Thomas Nosker, an assistant research professor in the Department of Materials Science and Engineering and principal investigator in the Center for Advanced Materials via Immiscible Composite Materials at Rutgers University. The late Richard W. Renfree, Nosker's graduate student who later became a Rutgers professor, helped invent the revolutionary material.

"People complain about plastics because they don't degrade," Nosker said. "We found a way to turn that to our advantage with a product."

That product is increasingly used to build bridges on U.S. Army bases and elsewhere -- docks, picnic tables, park benches, parking lot stops and other structures across America and overseas. It's been used to make about 1.5 million railway ties in the U.S. alone.

Since each tie weighs about 200 pounds, that means roughly 300 million pounds of plastics have not ended up in landfills, won't choke marine life and won't soil beaches.

Nosker, a prolific inventor, and his colleagues have been on the leading edge of plastics research for decades. They developed several types of structural recycled plastic lumber, a standard way to test plastic lumber, fire retardants for plastic lumber and machines to make plastic lumber.

All told, Nosker co-holds 28 patents or patents pending in the United States, in addition to overseas patents, reaping millions of dollars in revenues for Rutgers.

Thirty years ago, Nosker, now 59, was a doctoral student at Rutgers trying to deal with growing mountains of discarded containers. Plastics were rapidly replacing glass for packaging milk and soda - two high-volume grocery products - and ending up in landfills.

Nosker and others devised ways to sort, clean and process soda bottles made from polyethylene terephthalate (PET). They sold the material for a profit to make rugs and insulated jackets, stuff mattresses - even produce new soda bottles. Far more problematic was another type of plastic waste - known as high-density polyethylene (HDPE) - that was used to make milk containers.

"Prices for HDPE were so low that you couldn't even afford to wash used milk bottles in preparation for recycling," Nosker said. "But we couldn't just turn around and throw it away. Plastics experts said it was potentially recyclable, and we wanted to work on that."

Initially, Nosker and his colleagues tried making bottles into a substitute for chemically treated wood used in park benches and decks. But recycled HDPE planks sagged over time, when people repeatedly sat or walked on them. Some researchers tried combining HDPE with other plastics used to package foods and household goods, but had little success.

"We combined HDPE with polystyrene from old Big Mac containers," Nosker said. At a specific proportion, the blended plastics gained strength because of the way tiny plastic particles interlocked.

Making the leap from creating strong recycled plastics to using them to build objects traditionally made of wood required an innovative show-don't-tell strategy. For centuries, wood lumber from trees has been the go-to durable, flexible and affordable raw material for construction.

But wood has its drawbacks; because it needs protection from insects, other animals and the elements, it is often treated with toxic preservatives that can leach into the soil, water and groundwater, posing risks to people, animals and plants. Structural recycled plastic lumber, which is mostly polyethylene reinforced with stiffer plastics or recycled composites like car bumpers, does not pose such risks.

So 18 years ago, Nosker and Richard G. Lampo, a materials engineer at the Construction Engineering Research Laboratory of the U.S. Army Corps of Engineers in Champaign, Illinois, built the first structural recycled plastic lumber bridge for vehicles at Fort Leonard Wood in Missouri.


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