April 24, 2001

Cornell Chemists May Have Struck Gold in Rubber Plastic

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In the near future, the price of your new sneakers may decrease thanks to Cornell researchers. The researchers have created a new class of rubbery plastics that can be inexpensively produced from ethylene and propylene, two common and inexpensive petroleum derived chemicals.

Geoffrey Coates, assistant professor of chemistry and chemical biology, assisted by graduate student Phillip Hustad and postdoctoral researcher Jun Tian, discovered a titanium based catalyst that allows the new polymer to be made. A catalyst is a compound that speeds up a chemical reaction without itself being consumed in the reaction.

This catalyst “allows us to make a class of polymers no one has ever made before,” Coates said.

Since the 1950s, scientists have been working on metal-based catalysts, and right now there are only five other ones that work in a similar fashion as the newly discovered catalysts. However, “what sets our catalyst apart from the other catalysts is that it works with ethylene and propylene to make the elastomer,” Hustad said.

Similar polymers are currently made from styrene and butadiene, two relatively more expensive chemicals than ethylene and propylene.

According to Coates, the polymer is produced using a “living polymerization” process, where the ethylene and propylene are connected in an endless chain.

Specifically, this polymer is made of three repeating pieces. It starts with a piece of propylene in a hard form called syndiotactic propylene. This piece is then connected to a piece of ethylene-propylene co-polymer, which is soft. Finally, another piece of the hard syndiotactic propylene is added to the end.

It is the combination of the soft piece between the hard pieces that gives rise to the rubbery properties of the polymer, according to Coates.

Coates compares the process of “living polymerization” to a pasta machine, which produces spaghetti, then linguine, and then spaghetti, all connected together.

Before the discovery of the catalyst, scientists could produce the spaghetti and linguine, but couldn’t keep the two connected. With this catalyst, “we found we had a catalyst that could go on for a whole day,” Coates said.

Rubbery plastics, such as this one, are called thermoplastic elastomers and have the property that they can be melted and recycled.

“You can heat up little pellets of this rubber and it will melt. You can easily recycle them and make new types of materials out of them,” Coates said.

These types of rubbery plastics have many uses, including roofing materials, adhesives, and even shoe soles.

Since this is a completely new class of polymers, its properties will need to be tested.

“Based on the properties, we will decide if its worth pursuing commercially,” Coates said.

Coates presented his research at the April 3 national meeting of the American Chemical Society and, according to Hustad, the Journal of the American Chemical Society accepted the research paper for publication.

Archived article by Luke Hejnar