UA team discover process to turn waste sulfur into plastic

2013-12-01T00:00:00Z UA team discover process to turn waste sulfur into plasticBy Drew McCullough Arizona Daily Star Arizona Daily Star
December 01, 2013 12:00 am  • 

Science requires a lot of hard work and a little bit of luck.

Both came into play for a UA professor and his research team. They invented a new chemical process to make plastic out of liquid sulfur for the first time.

Jeff Pyun, University of Arizona associate professor of chemistry and biochemistry,  began this project in 2010 when the UA gave him funding to explore a new area of batteries.

Pyun said he didn’t want to work with lithium-ion batteries, which are the most common in portable electronic devices, because it would be hard to distinguish himself in that area.

Instead, Pyun turned to lithium-sulfur batteries, which have a lot of potential and one big drawback.

Pyun said lithium-sulfur batteries store five times more energy than ion batteries, but they don’t last nearly as long.

“Typical lithium-ion batteries can go through 500 to 1,000 charge-discharge-charge cycles,” he said. “For these lithium-sulfur batteries, you’re dead before even 100 cycles.”

Pyun and his team made it their goal to give lithium-sulfur batteries a much longer lifetime. The team then began studying the chemistry of sulfur.

“Sulfur is great for things like batteries and optics, but it’s really hard to work with,” Pyun said. “No one’s developed any chemistry to work with it. It doesn’t dissolve in most things, and you can’t melt it like a plastic — it’s just evil.

“We were the first to melt it and do chemistry in this liquid-molten sulfur,” Pyun said. “We did that and had a plastic in one step.”

Jared Griebel, a UA graduate student of chemistry and a member of the research team, discovered the co-monomer to mix with liquid sulfur that ultimately led to success.

Griebel, who was named the UA’s Student Innovator of the Year for 2013, found that by mixing 5 to 10 percent of DIB, an inexpensive, common precursor of plastics, with liquid sulfur, it made a stable plastic.

Griebel demonstrated how the 10-minute process works in a recent visit to his lab. He said the beauty of the process is how simple it is to complete.

The team coined its process as “inverse vulcanization” because it’s basically the opposite of vulcanization — a process invented by Charles Goodyear in which small amounts of molten sulfur are added to rubber to make tires.

The term was especially appealing to Pyun, who said his team’s story is similar to Goodyear’s.

Goodyear invented vulcanization in the 1800s when he accidentally knocked a container of sulfur into an experiment he was looking at and the substance turned into a tire-like material. Pyun said his team also made its discovery from luck.

In addition, “we share the same birthday — April 26,” Pyun said. “It’s a very eerie coincidence.”

When the team used the new polymer to make a battery, it found that it worked much better. The team is now exploring other uses for the new polymer and offering it as a solution to the waste-sulfur problem.

Pyun said the team’s new sulfur plastic could help to make lenses much thinner for glasses or cameras because it has a higher refractive index than most high-refractive things.

Pyun and his team also realized that if they found an everyday use for their product, they could have a beneficial impact on the environment.

“There’s tons of sulfur in the world,” Pyun said. “We call sulfur the ‘garbage of transportation’ because before the oil companies can sell you gasoline, they take out the sulfur” through a process called hydro de-sulfurization.

There are very few uses for the extracted sulfur, so oil companies place it in large mounds that grow exponentially every year, he said.

Pyun said: “There’s more sulfur in the world than we know what to do with. The average American easily generates their weight in sulfur every year.

“In addition to the battery stuff,” Pyun said, we thought, “If we could be the first to think about how to take all of this (waste sulfur) — that could be not only for energy, but also for sustainability and the environment.

“That’s kind of the mantra of our group,” he said, “from garbage to plastic to energy. That’s the way we think about this.”

Pyun said his team is working to find a company to manufacture the plastic and battery on a commercial level. He said he has attracted lots of interest, but couldn’t mention the companies yet. The team’s application for a patent is being reviewed by the U.S. Patent Office.

Although Pyun is the leader of the research team, he said: “All the credit goes to my students and post-docs.

“They’re the ones that actually go in the lab and make things happen with a whole lot of blood, sweat and tears,” he said. “I think that it’s really the love of science and the love of the unknown that makes this group of young people extraordinary.”

Griebel said that although he might have discovered which chemical process was successful, it was a team effort.

“We’re actually a really small group,” Griebel said. “There are currently four grad students, two post-docs and three undergrads.

“Being able to hold our weight and fight pound per pound versus some of the bigger-name people in the country on chemistry, I think that really shows the caliber of research we do,” Griebel said.

Drew McCullough is a NASA Space Grant intern at the Arizona Daily Star.

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