Greener Plastics

“Most plastics are made from oil-based resources, and just as the price of gas goes up, the price of plastics go up, as these resources become more and more precious,” Coates says. "Carbon dioxide is extremely inexpensive. Arguably, for most resources, it's a free chemical compound."

Carbon dioxide is stable-- it's hard to make it react with other chemicals to form new materials. But Coates and his colleagues were able to design special molecules called catalysts that can drive these reactions.

They started up an Ithaca-based company, called "Novomer, Inc.," to develop these new plastics into products.

"These plastics can be used for basically anything where common plastics are currently used," he says. “They also have many special applications because they decompose really cleanly when you heat them, so making ceramics, high-tech electronics… making cast iron and cast aluminum engines, these plastics have a lot of really important potential uses.”

In fact, the company’s first commercial product, announced last week, is a specialty plastic designed for use as a sacrificial binder— a substance that acts as a temporary adhesive during precision manufacturing and is then removed, ideally by burning it away. 

Novomer chemical engineer Jeff Conuel explains: “The customer would take it into solution, put it in place, it holds stuff in place during the manufacturing operation, and then when they’re done with that they heat it up a little bit and the polymer just goes away, leaving little or no residue behind, nothing to interfere with the manufacturing parts.”

Destroying the polymer releases carbon dioxide and water, not toxic byproducts. “It’s pretty neat,” says Conuel. “It’s a novel material-- no other materials can perform like that.”

Coates says that while it hasn’t previously been impossible to use CO2 in plastics, it has been way too impractical.

“It’s important that if you have to use a lot of the catalyst or if the catalyst is really expensive, if the catalyst is really slow, that making the polymer becomes very expensive. So ideally, you want a catalyst that converts the feedstocks into the plastic in a very quick time scale. So if you’ve got a really expensive chemical factory, you don’t have to wait for weeks worth of reactions to take place,” he says.  “Our catalyst is significantly faster than any of the other  catalysts that are out there.”

Not 100%

The company’s goal is to make plastics out of 100 percent renewable resources, but 50 percent CO2 is likely the limit.

“Nature makes its plastics out of carbon dioxide completely, although it does a lot of chemical processing and using photosynthesis,” Coates says. “In our plastics, we have to use another molecule because carbon dioxide itself has very little driving force, so it’s a very stable compound, so we have to add these helper molecules to make the plastic form,  which at the current time is based  on oil.

“One of the things we’re doing at Novomer is trying to find non oil-based resources for this other part of the polymer so that at the end, the entire plastic will be made out of renewable substances,” he says.

And unlike conventional plastics, the new plastics are biodegradable.

“If somebody were to use this plastic and accidentally leave it in the environment, unlike polyethylene or some of the other common polymers that'll exist in the environment for decades, if not centuries, these polymers degrade under relatively short time scales,” says Coates. “So we won't have unwanted plastic dispersed in our environment."

Not Off the Hook

The researchers, who are indeed concerned about the environment, say none of this lets us off the hook when it comes to recycling, or conserving energy.

“Our long term goals include packaging,” writes Novomer’s Erik Hoover.  “For example, we see opportunities to blend our materials with other biodegradable plastics, giving better properties, farther down the timeline.  But waste stream and end-of-life issues are complex.  We don't like to imply that people are off the hook for their behavior. So, the chemistry that makes biodegradable plastic is just part of the solution.”

And Coates points out that it will take many different solutions to solve global warming. “Of the oil that we use every year, about 90 percent is used for energy. The other 10 percent is used by the chemical industry. Of that 10 percent, about 90 percent is used to make plastics,” he says.  “This might help in reducing the amount of CO2 that enters the atmosphere, but realistically, it’s only going to make a very small dent.”

Conuel says it’s exciting to at least be part of the solution. "To be able to take somebody's waste product and turn it into something that's really useful, is great," he says.

This research was published in Angewandte Chemie, November 2004; US patent 7304172 to Cornell Research Foundation, December 2007, and funded by the National Science Foundation, US Department of Energy and private investors.