January 28, 2005

Researchers Create Plastic From Oranges

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Oranges and plastic don’t usually go together, but Cornell researchers have found a way to make plastic from limonene, an oil in orange peels.

For the past six years, Prof. Geoffrey Coates, chemistry and chemical biology, joined later by Scott Allen, post doctoral associate, and Chris Byrne grad, have been working on developing polymers especially from renewable resources.

They tried using limonene oxide and carbon dioxide to make polymers instead of petroleum-based compounds. According to Allen, over the past years, the research team has had the goal of making plastics either entirely, or in part, from renewable materials. One benefit to using renewable resources is that, according to Coates, petroleum is a limited resource and is increasing in price.

“It’s just that it’s a lot easier and cheaper to make polymers out of petroleum,” Allen said.

Limonene makes up about 95 percent of the oil in orange peels. According to Byrnes, limonene oxide has similar properties to polystyrene, a compound from petroleum. Orange peels are one of the most abundant sources of limonene, but the compound can also be obtained from over 300 plants, including pine bark, other citrus fruits and byproducts of the paper industry. Limonene can then be oxidized to make limonene oxide. The research team used the new zinc-based catalyst to allow the limonene oxide and carbon dioxide to react and produce the polymer polylimonene carbonate.

Limonene oxide and carbon dioxide will not react on their own, so the team developed a zinc-based catalyst to enable the reaction to proceed.

“We’ve got the only known catalyst for this reaction,” Coates said.

The study, “Alternating Copolymerization of Limonene Oxide and Carbon Dioxide” was published in the Journal of the American Chemical Society last fall. According to Coates, there has been a growing interest in making plastics from renewable resources.

“We are working with local startup company Novomer in looking at properties and potential applications [of the polymer],” he said.

“Lots of people want to know the properties: how strong is it, is it stretchy, brittle, or tough,” Byrnes said.

Future work includes finding out more about the properties of the polymer and how to improve efficiency of polymer synthesis.

“This is still in the discovery stage, right now the chemistry is very new,” Allen said.

Cargill Dow, a Minneapolis-based company, has been making plastics by fermenting starch from corn. Grocery stores are starting to sell produce and deli cuts packaged in polylactic acid, a polymer from corn, which is biodegradable.

Archived article by Vanessa Hoffman
Sun Staff Writer